White Paper Discuss: Nothing But Dewalts
 

Thread created automatically to discuss a document in the White Papers.

Nothing But Dewalts by Joe P

Re: White Paper Discuss: Nothing But Dewalts
 

Great! Thanks Joe and Joe. I'm disappointed to see that its a bit more work than I had thought, but after the additional testing that OCCRA gave it, I think we can be assured that its up to the job.

I thought Joe Johnson had said that he had interfaced the drill motors with it, too. Is this true?

Finally, what exactly does Lou Odin provide in this kit of his? The aluminum and plastic plates for the Chiaphua, neccesary bolts, and the modification of the sun gear? What kind of lead time can we expect during build?

Again, thanks for the great work.

Re: White Paper Discuss: Nothing But Dewalts
 

MAx,
The kit id Drawing 1,2, 3, and 5. You have to send him the carrier gear to be modified.
Yes you can interface the drill motors however we didn't do it in this paper because they may not be in this years kit.

Re: White Paper Discuss: Nothing But Dewalts
 

Great paper - thanks so much for those details. Have any of you done any testing to determine the motor "curves" (torque/speed/current data) for the various motor/transmission assemblies at different reduction settings (1st, 2nd, 3rd gear)?

Re: White Paper Discuss: Nothing But Dewalts
 

Is there any reason that the Globe and Fisher Price versions are shown without a shifter?

Re: White Paper Discuss: Nothing But Dewalts
 

This is Very Cool. Thanks joe for the whitepaper. even though this maybe be time consuming, its definitely worth it. and its not even that much money only 65 dollard. Again, Thanks Joe. :)

Re: White Paper Discuss: Nothing But Dewalts
 

No reason
I did it on the Chiaphua and didn't want to repeat it over again in the paper.

Re: White Paper Discuss: Nothing But Dewalts
 

It is because the shifter is on the transmission side and therefore can be coupled with any of the motor transmission combinations relatively easily. Last year we drove with the motor transmission described without a single issue or repair of the motor transmission set.

Re: White Paper Discuss: Nothing But Dewalts
 

There is one mistake in the paper that I want everyone to know about.
Page 17 - Step 3. for the Fisher Price - The distance from the top of the pinion gear to the front of the motor case should be 0.72 inches. not .072 inches. Had a bad day with decimal points.

Re: White Paper Discuss: Nothing But Dewalts
 

STU,
We just got a prototype chassis running with the CIM Dewalts. We haven't had time to think about this yet. Maybe someone on Team 47 has done some work on this, I don't know?

Re: White Paper Discuss: Nothing But Dewalts
 

Why did you decide to throw out the first stage of the DeWalt for the CIM interface? Did you find a problem with using an input pinion as in the other arrangements?

So these modules were attached to the robot only by the aluminum clamp? Did you ever have problems with slippage?

Thanks for sharing this paper. I had been looking to discard the yellow clamshell, but I'm impressed by your use of it.

Re: White Paper Discuss: Nothing But Dewalts
 

I'm not sure what their reason to discard the first stage for the CIM was, but there is a very good reason I can think of. The gearbox is surely designed for a very high rpm, low torque motor (like the drills from our kit of parts) and the CIM probably has 2 or 3 times the torque of the motor it was designed for. A mas produced gearbox like this is most likely engineered down pretty close to the specs its needed for. It wouldn't take 2 or 3 times the torque.

Re: White Paper Discuss: Nothing But Dewalts
 

My notes say the advertised output torque for the 18V XRP drill is 500 inch-pounds = 56Nm. The stall torque of the CIM (at 107A) is 2.2Nm. So the CIM put through the 46:1 reduction of first gear represents a 101Nm output, or just about twice the number DeWalt puts on the box.

I know someone out there was building CIM-Bosch-DeWalt combos in the off season, and I'm under the impression that the DeWalts survived that fine. Does anyone know if they were using the full reduction?

Re: White Paper Discuss: Nothing But Dewalts
 

Just a note, the CIM assembly involves dropping the first stage of the transmission, so the gear reductions on the CIM assembly are 3:1, 4:1, 12:1. The CIM puts out .79Nm at 40A (which was the amp limit last year) so after the 12:1 gear reduction, the whole assembly puts out about 9.5Nm (assuming I did math right of course!).

Great paper Joe, thanks for posting it. Hopefully more teams can have shifters with this method, since it is so much easier and cheaper than building one from scratch.

Edit: Jim, I believe that Andy Brockway and Team 716 were the people trying out the XRP transmission with the FP and Bosch motors linked.

Re: White Paper Discuss: Nothing But Dewalts
 

Thanks Ryan. I was responding to Max's suggestion that retaining all three reduction stages (not what Joe P recommends) might lead to a gearbox failure. Personally, I think that the XRP can probably handle twice its rated torque-- but thats just a gut feeling.

Although I am aware that the CIM outputs only .79Nm at 40A, it must be remembered that our 40A breakers can actually sustain upwards of 80A for short durations. Using the 40A number, even with all three stages we remain well under rated torque for the transmission. In my calculation I used the stall current to be conservative. I am curious what the real maximum momentary load from a CIM motor is, once you factor in our breakers and our non-ideal voltage source.

Re: White Paper Discuss: Nothing But Dewalts
 

I too am confident the Dewalts can take 2X the published numbers.

As to the 40A fuse letting much more than 40A through for short periods, this is a certaintly. "Short periods" are essentially infinite time for the gear teeth in that once they are broken, they are broken. Beyond this, there is the problem of static vs. dynamic loading.

BUT... ...I really question the need for a 47:1 ratio with the Chiaphua motor. 47:1 with 3 planetary stages will provide effectively 34:1 which would give you 70+ N-m With a 12mm (.5") radius sprocket you'd get 6000N (1400 lbs). That is a lot of force!

Beyond this, the sprocket woud be turning at a mere 2 Rev/Sec. Not very speedy.

Re: White Paper Discuss: Nothing But Dewalts
 

This is a thing easily done. The planetary gearboxes should be pretty close to the "published" efficiencies of 85-90% for each planetary stage (with these low ratios per stage -- higher ratios like 10:1 in one stage can be VERY inefficient).

This would mean that in 2nd & 3rd, the gearbox should be 70-80% effecient and in 1st, the gearbox should be 60-70% efficient.

Note well that effeciencies apply to TORQUE not speed. The speeds are simply divided by the ratio while the torques are multiplied by the (ratio X eff).

Given this data, it is a simple matter to go into DrJoesMotorCalc spreadsheet and get any speed-torque curve your heart desires.

Joe J.

Re: White Paper Discuss: Nothing But Dewalts
 

Yes, I agree with Mike A. The shifter can be applied to any gearbox easily. The WHY is an open question, but I can think of reasons to apply the shifter to other gearboxes.

It is possilbe that future FIRST games will involve balls. One of the things about ball handling is that it is nice to have FAST rollers but with fast rollers that JAM come high current and (perhaps) toasted motors. One may decide to put a shifter on the ball roller transmission to allow for jams to be cleared in a low gear while normal operation involves the higher gears.

Also perhaps you want to drive with the Fisher Price AND a Chiaphua, you may just put 2 Dewalts on each side rather than going to the bother of designing a 2 motor input to one Dewalt. In this case, a shifter on both a F-P and a Chiaphua will be nice.*

Joe J.

*Note that FIRST will have to open up the rules on servos to make this legal because only 2 per robot were allowed in past years.

Joe J.

Re: White Paper Discuss: Nothing But Dewalts
 

The Bosch drill motor is perhaps the easiest to motor to make work with the Dewalts: Buy a Dewalt motor, press off the pinion gear, press it on the the Bosch motor, Bore out the motor adapter for the Dewalt to hold the Bosch, Install the motor.

But... ...FIRST had a fire sale on the Bosch motors so I suppose they are not in the kit.

The seat motor is very very easy to use too, but, I have a suspicion (not inside knowledge, but a suspicion) that Keyang is in the same (lousy) position the rest of the auto industry is in and therefore, I think perhaps they are not going to come up with $20K of motors for free for FIRST.

Given my suspicions and my lack of a "spare" to send Joe P for him to reverse engineer, the details of how to implement the Keyang modifications is left for an exercise for the reader. (Lou Oudin will make you the square hole sun if you want -- FYI)

Joe J.

Re: White Paper Discuss: Nothing But Dewalts
 

We don't know what we are going to do with them but we are sure we will need them.

ASAP we'll be kickoffing off

4 Chiaphua (CIM) transmissions,
3 Fisher-Price transmissions (the extra Mabuchi is the same form factor as the F-P, according to Paul Copioli, it may be the same performance too), and
2 Globe transmissions...

...9 more yellow power packs for CD10. NBD baby... NBD!

Joe J.

Problems? Questions? Successes?
 

From the website I see that 500+ folks have downloaded this whitepaper, perhaps more copies have been shared from person to person.

There have been some relatively positive comments, but... ...I am curious how things are working out.

Initially, I had some e-mails asking about what to do when DewaltServiceNet.com shows backorders of some parts with longish scheduled delivery times.

Right now for example the following important parts are on backorder:


394514-00 MOTOR ADAPTOR
395666-01 GEAR CASE ASSY

My experience with Dewalt is that they almost ALWAYS beat their promise date BY A LOT. For example they were out of clamshells last week with a promise date of late Feb. The clamshells are shown as in stock right now.

Another way to get the parts is to call your local Dewalt Service dealer. They have access to stock that is not shown on the dewaltservicenet.com site.

Finally, you can always use The Home Depot (or equiv.) as a source. The whole drill is only $150 or so (less if you can find them on sale -- even less if you can find them on ebay or elsewhere).

Please let us know what goes well or what goes lousy for you. In particular, I am curious how many folks are using Lou Oudin at Capital Tool and Die for your modification source. I like Lou a lot and I think he will give you good service at a fair price.

Joe J.

P.S. Just to be clear, I have no financial interest in Lou Oudin or Capital Tool & Die.

Re: Problems? Questions? Successes?
 

I sure hope you're right. I just checked my order status. When it was originally placed the clamshells were on backorder. They are still on backorder until 1/21/05, and NOW the Gear Case Assy is showing backordered until 1/24!! :ahh: :ahh: :ahh:

I think I'll visit ebay!

Re: White Paper Discuss: Nothing But Dewalts
 

Can someone explain the purpose of the plastic "top hat" for the CIM modification? Is it some sort of bushing to support the shaft? Is it absolutely neccesary? Do the screws holding it to the carrier gear actually need to transfer much torque, or is it just to press it up to the gear?

Re: White Paper Discuss: Nothing But Dewalts
 

The sole purpose of the tophat is to keep the shifting ring from the second gear stage of the Dewalt transmisssion (which, just for clarity sake, becomes the first stage of the gearbox on the Chiaphua design because the normal first stage is eliminated) from tilting out of alignment.

Normally, the ring from the first gear stage keeps this second ring from tilting, but with the entire first gear stage removed, there is nothing but air to do this.

As to torque, there is no torque needed at all. In fact, there is no reason to have more than 2 screws. We just used 4 because there were four planets on gear stage one, which suggested to us to use 4 screws. Absolutle overkill.

Joe J.

Re: White Paper Discuss: Nothing But Dewalts
 

Alright, so there is no reason to even widen those holes (hardened steel isn't so fun to machine). Just find some small enough screws or other fastener.

Re: White Paper Discuss: Nothing But Dewalts
 

In actual fact there is no reason that the part can't be held in place by a shaft spacer. I never really thought about it, but you could just buy this part (6436K132) from McMaster.com and us that to keep the plastic tophat from backing off from the gear you press on the Chiaphua shaft.

In fact, if you could find a washer with at 5/16 hole and 1.650 or so OD, you could probably eliminate the tophat entirely (together with the above and a standard 5/16 washer)

Good thinking.

Joe J.

Re: Problems? Questions? Successes?
 

STU,
I am having problems getting the clamshells also. I reordered the clamshells
part # 394511-00 and got them in 5 days. If you look at the different model numbers of the cordless drills you can find substitution parts you can use. Our local Dewalt Dealer is helping me with this problem.

Joe P

Re: White Paper Discuss: Nothing But Dewalts
 

can someone post some quick deminsions of the dewalt assemblies....notable the fisher price combo. the nominal length of the entire tranny, the dia. of the neck and the length of the neck. just rough dimensions will do. thanks.

Re: White Paper Discuss: Nothing But Dewalts
 

I wanted to offer that the clamshells for the 12, 14.4 and 18 volt cordless DeWalt XRP's are interchangable for our purpose. My team also had some luck turning up limited quantities of parts with froogle.com. Also, MaxTools.com will sell you the appropriate 14.4V XRP drill for $99 + $10 shipping a piece. Unfortunatly, our local DeWalt Dealer has been unable to help us.

Re: White Paper Discuss: Nothing But Dewalts
 

Thanks guys! In fact I am aware of the interchange-ability for our use between the 12V, 14.4V, and 18V models. I am attaching a spreadsheet that I generated with all of that information, including Dewalt ServiceNET pricing for needed parts (non-common parts are highlighted).

I think I have found a source for the 12V model (DC980KA) for around $75 (without battery) INCLUDING shipping. Now we just have to see how quickly they get here!! :ahh:

I will check on available quantities and report back (including shipping info)...

Re: White Paper Discuss: Nothing But Dewalts
 

We have extra clamshells now and you guys are located near.
Give us a call and if you need clamshells, help or advice we are willing.
254-501-0987

Joe P
Team 647 Shoemaker Cyberwolves

Re: White Paper Discuss: Nothing But Dewalts
 

i think that they are interfaced to drills, but you dont need that this year (no drill motors. :D :D :D

Re: White Paper Discuss: Nothing But Dewalts
 

Forget about the motor, the best part of the Dewalt XRP drill is their TRANSMISSION!

Read the paper, see if you don't agree.

Joe Jl

Full Disclosure
 

I have gotten this question via e-mail:

Here is my reply:

I make no guarrantees, but I believe that you will have a good result with this solution.

I thought I would share this exchange with folks in the interest of full disclosure.

Joe J.

Re: Full Disclosure
 

After thinking about what you had suggested about using a shaft collar and washer instead of the top hat, I thought I might as well use the shaft collar to help transfer power, too. You can bolt the carrier gear to the shaft collar and not worry about the press fit.

Re: White Paper Discuss: Nothing But Dewalts
 

can someone please toss me some general dimensions for the stock dewalt transmission. i don't have one in hand yet...any general length and width dims would be appreciated. thanks.

Re: White Paper Discuss: Nothing But Dewalts
 

If you are talking about the version mated to the CIMs without a servo, I can help you. I used some pixel counting on the pictures in the document (so this is all pretty approximate) and got the following.


Distance to 1/2" shaft from large face of CIM 3.7"
max diameter from CIM to 1/2" shaft 2.7"
1/2" shaft with sprocket, bolt, etc 1"x1" cylinder

Re: White Paper Discuss: Nothing But Dewalts
 

thanks for that. can someone who has one of these trannys, even a stock one take an overall length measurement from the end of the shaft. thanks you.

my assembly will be using the fisher price so i just need a general length measurement.

Re: White Paper Discuss: Nothing But Dewalts
 

Overall length of Fisher Price/Dewalt Assembly is about 8.25 inches. Diameter is 2.5 to 3 inches dependindg on where you measure.

Joe P

Re: White Paper Discuss: Nothing But Dewalts
 

thanks

Re: White Paper Discuss: Nothing But Dewalts
 

The paper suggests that "software synchronization" may be possible for shifting the transmissions. I believe I understand what synchronization is in a shfting transmission; it's waiting until whatever you are shifting is lined up with whatever you are shifting into so that no grinding of gears or shifters occur. Now how could this apply to the DeWalt transmission? How could you tell when the gears are in the right position to shift?

Re: White Paper Discuss: Nothing But Dewalts
 

First off I want to say that this is a great white paper. It makes it a lot easier to start more teams in an area with a small mentor base with ideas like this and AndyMark. I can't wait to try my first DeWalt transmission!!

I do have a couple questions while I wait for my order to come in.

What modifications are required to the fisher price pinion?
Has anyone mounted a gear to 1/2" shaft? My first impression is that a gear would produce a smaller side load but without a transmission in hand I may be missing some issues with mounting accuracy.

Thanks again!

Re: White Paper Discuss: Nothing But Dewalts
 

same for me.......did anyone toss a spur gear on the drill output last year......if so with what implications?

Re: White Paper Discuss: Nothing But Dewalts
 

The paper describes this.
Modify motor adaptor
Make a plate that holds motor to adaptor
Get Planet2 from extra transmission,
enlarge hole to 1/8,
press off 13T that is on FP,
press on 1/8 bore Planet2 onto FP
Mix well... ...Done!

Sprockets, gears, same same. The pitch radius essential determines the side load. One is as easy as the other. If you like, gears you can do the same thing with a gear that we suggest you do with a sprocket.

Joe J.

Re: Full Disclosure
 

That sounds like a great idea to me. Any comments Dr. Joe?

Re: White Paper Discuss: Nothing But Dewalts
 

thanks for the fast reply. just for the record Dr. Joe....Dennis and I are using six dewalts so far. in fact it's nothing but dewalts except for the globe motor, but he didn't need any help.....so he's flying solo.

i don't have one in hand yet, but we're excited to give em a go.

Re: White Paper Discuss: Nothing But Dewalts
 

I just checked the status of my Dewalt order. I had been hoping to see part of the order waiting for me when I got home today. When I placed the order, the motor adapter was on backorder until 1/24. Now it’s listed as back ordered until 2/11, and this was an alternate, P/N 626494-00. But this may be entirely moot because the transmission is now listed as out of stock and no back order date is listed. Hopefully the local service center is open tomorrow and can help me out.

Re: White Paper Discuss: Nothing But Dewalts
 

If I buy the 12 Volt Dewalt Drill, the DC980KA, do I have all the parts I need to make the CIM / Dewalt tranny? I think I do except they only give you one of the screw you need two of? I really need help on this quick, thanks.

Re: White Paper Discuss: Nothing But Dewalts
 

A complete drill will have all the parts you need for a Chiaphua / Dewalt, including screws.

Joe J.

Re: White Paper Discuss: Nothing But Dewalts
 

Steve,
Part 605256-01, in the BOM should be 1 not 2, the reverse threaded screw that goes in the end of the 1/2in.- 20 output shaft. I still need to do a revision to this paper.

Joe P

Re: White Paper Discuss: Nothing But Dewalts
 

Hey guys thanks a lot, We should be getting one soon to see if we want to use them this year. Ill let you know how it turns out.

Re: White Paper Discuss: Nothing But Dewalts
 

Another question, do the 12 voilt, 14.4 volt, and 18 volt drills with the 3 speed all have the needed parts and are basically the same? Was wondering if I needed a specific volt drill or if they all will do.

Re: White Paper Discuss: Nothing But Dewalts
 

As far as we are concerned the 12, 14.4 and 18V XRP drills are the same. The motor is different and there may be some differences in the electronics and/or how the battery plugs into the clamshell, but all the parts that matter are the SAME part number.

FYI, the Hammer Drill is slightly different I THINK that it would be possible to change some of the dimensions and make it work, but I have not actually done it.

Joe J.

Re: White Paper Discuss: Nothing But Dewalts
 

Whats the torque rating on the chippua stripped down version of the transmission? can you take the chippua and run it through a gearbox first? or is that too much of a load ?

Re: White Paper Discuss: Nothing But Dewalts
 

Check my spreadsheet (right click -> save as) attached to this post. Drill model numbers that have the correct parts are:
12V XRP - Model DC980KA
14.4V XRP - Model DC983KA
18V XRP - Model DC987KA

Good Luck!!

Shifting Dewalt transmissions - LITTLE HELP PLEASE!
 

We have completed a couple of these SWEET CIM-Dewalt transmission combos and we plan to utilize their shifting capabilities :p . The only problem is that the shifter feels really stiff :ahh: . I have a lot of trouble believing that our puny little servos will be able to actually perform that function as shown in Joe P's FANTASTIC white paper. Anyone out there who can comment, either positively or negatively, regarding the servo method of shifting these monsters, or any other methods used specifically with these motors/trannys??

THANKS!! :yikes:

Re: White Paper Discuss: Nothing But Dewalts
 

Great paper guys thanks a whole bunch!! some teams are so gonna be taking an advantage on this one. :)

thankies again :)

Re: White Paper Discuss: Nothing But Dewalts
 

We need some help. We used the white paper to interface a fp motor to the Dewalt gearbox and had an issue. We could not tighten down the case all the way or the gearbox would bind up. We left approximately 1/8" of a gap and it ran fine. The only thing we can figure is the gear is pressed on to the wrong depth, although we checked it against the instructions in the paper and it was correct. Any suggestions?????? Seems to work for now.

Re: White Paper Discuss: Nothing But Dewalts
 

We went the dewalt route this year. The shifting is pretty smooth for us-- be sure you've removed the little springy piece of metal that makes the drill "click" at each speed position. Also, we found that if we really crunched down the case, the shifting got stickier and the gears bound a little more.

Re: White Paper Discuss: Nothing But Dewalts
 

i successfully mated the fisher price to the dewalt four times so far.......

did you make the aluminum spacer disk for the motor.......it is crucial for spacing and also stiffens the plastic housing against any warp. double and triple check your parts.............if you build exactly to print your motor should be running perfectly!

Re: White Paper Discuss: Nothing But Dewalts
 

Thanks for the advice. We will check it out further.

Re: White Paper Discuss: Nothing But Dewalts
 

Whoops, looks like our problem is the missing motor plate, sor some reason in our haste we forgot to make that, will have to see if we can get it in tomorrow.

Brian, we don't have that plate in front of the FP so it is probably in too far

Re: White Paper Discuss: Nothing But Dewalts
 

Is anyone using these for their drive motors and shifting them? I wondering if you use one on each side, will they simultaneously shift with the servos? What if you use four, one for each wheel? Will all four shift simultaneously?

Also, can a flex coupling (lovejoy) be placed on the end of the shaft? Will the threads in an aluminum one strip out?

Last, can the Chia gear be reamed on a manual lathe (with a proper reamer of course) instead of EDMed? If so, what size reamer would you recommend (considering the lathe is old and probably not incredibly perfect anymore).

Re: White Paper Discuss: Nothing But Dewalts
 

We used them last year, and again this, at all four wheels. We learned from last year's prototype that YES, all four would shift simutaniously, but it was a struggle. A giant servo was used via cables to shift them, but the #4-40 threads would pull out of the linkage.

We considered shifting again this year with one continuous cable (spectra cord) and a short throw pnumatic. But decided that the risk of getting one or more wheels caught out of gear was not worth it. I.E., six robots and nine goals on the field may not leave many fast lanes open - so we're locked in first gear.

Re: White Paper Discuss: Nothing But Dewalts
 

As to shifting wit a "Giant Servo," I don't know under what theory a Giant Servo would be legal under this year's rules or last year's rules.

But... ...be that as it may, if you shift with one Hitec 311 servo (i.e. a legal servo) per transmission in the manner shown in the white paper, the shifters have enough "guts" to shift. They sometimes need to have the gears moving to find the right mesh, but this has not been a problem. Eventually, the drivers move the joysticks, which allow the gears to mesh if a jam occurs.

As to shift on the fly, I have discussed elsewhere that this is possible. The transmissions don't sound like they like it, but they didn't fail either. We told our drivers to do it when they needed to and not to if they didn't. Also, as I've said before, the shifting can be enhanced with software if you monitor the speed of the output shaft and try to pick the right voltage to make the mesh go smoothly. It is not very complex code.

As to simultaneousness of shifting multiple transmissions, they shift close enough to at the same time that it didn't cause us any problems.

Some thoughts from THE Dr Joe... ...accept no substitutes ;-)

Joe J.

Re: White Paper Discuss: Nothing But Dewalts
 

same info here.....

we're using four dechip's(thats short hand for a cim and dewalt combo) to drive our base. we have one servo per tranny, to whitepaper specs.

we shift them on the fly repeatedly, at full speed, and even while turning. we've beat these things to death on our practice robot for over two weeks and have had no problems.

Re: White Paper Discuss: Nothing But Dewalts
 

Does anybody have the Drawings of the "Chiaphua Plate", "Plastic Top Hat", "Top Hat Carrier", and "Top Hat Chiaphua Assembly" i would like to make a large copy of the drawings for reference and other things but it is hard with the small copy on the whitepaper if anybody can help it would be greatly appreciated. Thanks


Bill Hancock

Re: White Paper Discuss: Nothing But Dewalts
 

Since this thread is resurrected anyways...

As a heads up to any teams planning on buying the CIM NBD kits from Capital Die, Lou Oudin is still doing them, but it's been a year since he last did, and he didn't get all that many orders last year, so you'll need to work with him a little more and have the white paper in front of you when you call. No problems otherwise.

Re: White Paper Discuss: Nothing But Dewalts
 

for everyone shifting plz rd if ur having problems (giant servo theory) http://www.chiefdelphi.com/forums/sh...ad.php?t=42461

Re: White Paper Discuss: Nothing But Dewalts
 

Years later, I'm finally looking at this and wondering if it'd be a good project for our team. We'd planned on building something similar on our own, but our driving directive for the future is, as I've probably mentioned elsewhere, the "12 Hour Drive." If we can't manufacture and assemble a drivetrain in 12 hours, I don't want to know from it.

So, I've got a few questions for folks that I've not seen answered elsewhere -- though I'll keep looking.

1. Is it possible to mount the servo plate (Drawing No. 5) onto the opposite side of the transmission housing than what is shown? I like symmetry and using as little space as possible for anything and everything.
   
2. Is mounting the assembly by a shaft collar genuinely sufficient? It seems like these assemblies can put out quite a bit of torque in first gear at stall and holding it place only by friction seems daring. Might it be better to adapt the Chiaphua Plate (Drawing No. 1) to mount directly to the robot in addition to the collar? I want to mount a gear to the output rather than a sprocket and am concerned that a collar will allow too much play in the center-center distance between the gears and create problems there.
   
3. We can laser cut .125" and .0625" delrin pieces and chemically bond them together to create a plastic top hat as shown in much less time than it'll take to set up and mill them. Will undersizing the .125" piece by as much as .003" be a disaster? The drawing calls for .128". I'd love to laser cut them, since I can then add a keyway in addition to the pressfit.
   
4. Is there a particular reason the modifications to the top hat carrier call for a counterbored hole rather than a countersink? Again, it seems to be it might be easier to countersink the hole than to counterbore it given our tools and desire to get it done quickly.
   
5. Is first gear really all that useful, or should I be treating this as a two-speed transmission? It seems like with gearing designed to make the two higher gears useful -- 1:2.5 at the output, resulting in about 1:7.5 and 1:10 -- the first stage reduction then becomes 1:30 and produces way more torque than even the stickiest of FIRST tires can be bothered with. Perhaps it'd be wiser to ignore that first gear all together, since I'm going to be spinning tires there in any case, and gear the second and third speeds down a bit more. 1:10 is awfully fast and 1:7.5 might be illegal on the Autobahn, even.
   
   

This looks like a really straightforward modification and I think we ought to be able to get two of these setups up and running in the time it'd take to set up and manufacture the parts for one of the gearboxes we'd otherwise been considering.

Re: White Paper Discuss: Nothing But Dewalts
 

Yeah, it's definitely doable. We've always put them on the same side because we would have a default setting on the servos which we used to calibrate them. If you have the servos on opposite sides. If you have the plates on opposite sides then one transmission might have a bias toward 1st gear, and the other might have a bias toward 3rd gear.

We had a debate about this on our team a couple years back, and trust me, those collars are more than sufficient. After 3 years of relying on the DeWalts for our drive train and arms, we've never has a single problem with the collars not being able to take the stress of competition.

Since they don't do anything else, I don't see why .003" would make any noticeable difference.

I think it just has to do with the type of screws they recommend in the whitepaper, but I'm not sure.

First gear is very useful. If anything, you might have more of a problem with the lack of difference between 2nd and 3rd. We designed our drive train to slip the wheels in 1st gear (using rough top on a 6wd). This maximized our speed while allowing us to still use the wheels' coefficient of friction as the limiting factor. In 2nd gear the robot would zip across the field, so we found that 3rd gear wasn't that useful, since 2nd gear was sufficiently fast for all practical purposes.

Re: White Paper Discuss: Nothing But Dewalts
 

I don't trust our ability to make a reliable press fit onto the CIM shaft, so I've been looking at alternatives. It seems like there's enough space on the shaft to allow for the "top hat" piece to be extended back to the motor mounting plate and keyed. Has anyone tried this?

Because we cannot conveniently (or, really, inconveniently) key hubs, I instead was considering that we build up a keyed "top hat" from layers of delrin or some other plastic. We can laser cut 1/8" and 1/16" layers as necessary and extend the overall length of the finished piece into the gap that currently exists between the motor mounting plate and the carrier/pinion gear. This'll get us about 1/2" of key and I'm going by gut when I assume that we can find a plastic that'll hold up sufficiently well this far up the gearing. We could then loosen or eliminate completely the press fit.



We'd be looking at stacking up this assembly on the motor shaft, gluing the layers togethers, then tapping through all of the pieces of plastic at once. Conceivably, we could try plasma cutting these same pieces from aluminum, but we've had mixed results with the plasma cutter, particularly because of its relatively large kerf. It's difficult to get it to make small cuts and holes cleanly.

Also, I'd love it if someone was able to tell me what the distance is between the back of the "top hat" and the motor mounting plate if this is built according to spec. in the whitepaper. The drawing doesn't include that information, nor the face width of the gears in the transmission, from what I've been able to tell. Based on the drawing below, I know only that the overall dimension from the face of the carrier gear to the motor mounting plate is .647" and that the top hat is .188".



I love the idea of making these work for us, but the build out called for in the white paper seems to call for all of our weakest abilities -- press fits, welding, accuracy ( ;) )... and the changes we're making to accomodate that seem significantly vast that we have some concerns. Still, for the weight and price, this arrangement can't be beat, it seems.

Re: White Paper Discuss: Nothing But Dewalts
 

Madison I respect your posts here on CD and I see your doing your best to try and make this work for your team. I don't think that using plastic as a key is such a great idea. This is coming from my background in machining and dealing with different types of plastic. I don't profess to be an engineer but my team has been machining plastic and using it for wheels,turrets and bushings for quite a long time. I have seen this set up and it just seems to me that in a application with the cim motor like you have shown the plastic keys just won't hold up through the whole season. I am only a first year engineering student but whenever there is metal on plastic, plastic usually loses no matter how strong it is after a certain period of time. I think your best bet would be to find someone who can make that size keyway which I believe is 2mm if your talking about the cim. Either that or make the Keyseat on the cim bigger and adjust the plate accordingly. Just a few ideas and I think aluminum would definitely be the way to go as far as the key. I like the idea it just doesn't seem efficient manufacturing wise and from what I read and I reread the post 3 times, that it just won't be durable enough. I do like an idea of a keyway in the top hat instead of a press fit, good thinking.

Just some input and ideas like you asked for,
Drew D.

Re: White Paper Discuss: Nothing But Dewalts
 

Drew,

Sorry if there was confusion -- I should've made this more clear -- but we'll be using a steel key seated between the CIM shaft and the plastic spacers. Last season, we built clutches for the 256:1 Banebots gearboxes that were delrin and acrylic and included the key in the delrin parts. Those keys didn't last very long at all and repairing them on the fly would've been impossible if we hadn't realized early on that we'd made a really dumb decision.

I'm not sure if we'd see better results with a steel key into a plastic keyway, though. It could end up being six of one and half a dozen of another.

Re: White Paper Discuss: Nothing But Dewalts
 

Madison,

Two years ago, we used a NDB CIM to spin up a shooter wheel. We too had a problem getting a good press fit on the shaft and ended up keying the unmodified top hat. Mind you, this was a last minute fix and the key ended up also being wedged somewhat under the metal gear... But it worked fairly well for us in that application. I'd probably be a little more worried about its use in a higher torque application, but not too terribly worried if you're lengthening the keyway. Seeing as how this is the off-season and all, I'd just recommend mocking up a similar keyed hole in something like a long, thin(ish) rectangle that you can rigidly attach to something. Then you can hook up a CIM (preferably that you don't like) and rig up something to stall it at 12V rapidly cycling from CW to CCW. One other thing I'd recommend is cutting your keyway as a semi-tight fit. Any slop you have there is going to increase shock loading by that little bit and make things that little bit less reliable.

Re: White Paper Discuss: Nothing But Dewalts
 

I just ran an FEA w/ the plate being 3/8 thick. At just two times the stall torque of a CIM, the keyway already had a lot of deformation. I really don't think it could take the repeated shock loads of being in the drivetrainn.

I have a question though, If you can cut the keyway into delrin, why can't you cut it into Aluminum? You have a laser cutter, right?

Re: White Paper Discuss: Nothing But Dewalts
 

Any chance you could post screenshots of your FEA results? What was the total deformation?

Our laser cutter can only cut plastic, for the most part. It has a hard time with polycarbonate, as it scores the edges, and melts polyethylenes, for example. It cannot cut reflective materials at all and just isn't powerful enough to get through metal of any useful thickness.

On the other end of the spectrum, our plasma cutter can fight through 1" thick chunks of steel, but its kerf is pretty bad and it does a bad job of cutting fine details in parts. For example, holes almost never end up being round by the time it's done :)

Re: White Paper Discuss: Nothing But Dewalts
 

It's coming to the gallery shortly.

Just to make sure my numbers make sense, I took the stall torque of the small CIM (343.4 oz-in) doubled it, and converted it to lbs (42.9250 lb-in). Then I divided it by 4mm converted to inches to get the force at 4mm (272.57375 lbs). I put a pin constraint on each of the 4, 4-40 holes (at .455 radius... taken from the whitepaper) and applied the calculated load to the keyway.

Does that sound right? Since I'm right out of high school I'd like it if someone verified this.... The sketch is in the NBD whitepaper, and took me 10 minutes from sketch to analysis.

EDIT: It's uploaded.

Re: White Paper Discuss: Nothing But Dewalts
 

Adam,

I ran more or less the same analysis just now. The true deformation isn't near as bad as your picture, you're looking at the scaled deformation. At any rate, the stresses are marginal at the stall torque of the CIM, but keys don't apply load on the keyway exactly like that in practice, and the worst stresses are at the corners of the keyway, and might be relieved by localized yielding in that area. Plus, the CIM is very rarely going to be stalled during actual use. So, again, I think the best test would be a mock-up to test the design in practice.

Re: White Paper Discuss: Nothing But Dewalts
 

If you're playing Defense it's feasible to stall the motors often. Also, everyone time you go from standing still to full voltage. And going from full forward to full reverse would put a good amount of load into it. I know the deformation isn't as bad as pictured, but that just seems like it would fail with the shock loads it will see in a match.

But then again, let's see a test; can't argue with the facts.

-Adam

Re: White Paper Discuss: Nothing But Dewalts
 

Risking embarrassment, I'll note that due to a bug in our PID code from shifting signed variables or something, the PID loop for the aforementioned shooter wheel had a fun quirk. When it overspun by a significant amount, it would throw the CIM into full reverse, or near to. Despite that crazy amount of shock loading, our bootlegged version of a keyway still held up. So I think things might work out better than you'd expect. If you still aim for some kind of press between the gear and shaft, that will also help relieve some of the load on the keyway.

Re: White Paper Discuss: Nothing But Dewalts
 

On a similar note, I talked to a team at Nationals who used a metal bonding agent (I don't know what the industry term is.... that's just what they call it where I work at Northrop) in addition to the press fit for the gear. How much of a difference does that make to the integrity of the press fit?

Re: White Paper Discuss: Nothing But Dewalts
 

JB Weld, maybe?

Re: White Paper Discuss: Nothing But Dewalts
 

So I was wondering if the Dewalts transmission worked good for all of you how have it made and running it on the robot? My team started making our first one, we arn't done yet and I was wondering if they help out or did you all thing it was more of a waste of time.

Re: White Paper Discuss: Nothing But Dewalts
 

My team used the Dewalts last year and they worked very well for us, we had some problems with shifting at our first event,but after we fixed the problem they worked wonders. It was nice to be able to go fast, to score and get away from defensive robots, and at the same time shift to be able to push back if we had to. We also used the low gear to climb up a ramp the one time we had to. I would say they are are not a waste of time, but it also depends on the game that is being played, if 3 speeds are not needed in the game then it may possibly be a waste of time, but they are a nice transmission to use, especially over the bane bots from last year.

Re: White Paper Discuss: Nothing But Dewalts
 

We have used the dewalts from the very moment Dr. Joe invented them.

Some comments:

To get the press fit correct you MUST wire EDM to exacting size.
We use a fixture to press on to the shaft of the motor for correct alignment and distance.
We created a fixture to control the sizes of the housings (we do no sand as per instructions) using a mill.

We do run 4 cims with 4 shifters that are in coordination....no issues

I believe the NBD System is still one of the easiest, lowest cost, reliable drive transmissions that all teams can make.

We have yet to have a transmission failure.

Re: White Paper Discuss: Nothing But Dewalts
 

I'd like to echo everything Dr. Joe said, especially about the EDM, and the fixtures.

Carbide will not work well to machine the sun gears. They are some ridiculously hard powdered metal. If you want to use these transmissions, you really must find someone to EDM them for you. It's quick, pretty simple, and most shops will be happy to do it for you.

There are two distinct variables that affect the CIM mate to the gearbox. One is the final length on the plastic housing, and the other is the press fit of the sun onto the CIM. Both of these will need to be quite accurate, or else you'll need to modify one or the other. We ended up doing this, but it's really not a good idea.

If you do choose to shift (not at all necessary, these gearboxes are amazing just locked into second gear!), you'll need to make absolutely certain that your shift ring slips well, and there are no binds. You'll also need a longer horn to get adequate torque- I recommend buying a new, longer one, and not relying on the adjustable ones that come with the servos. They slip.

Ultimately, the Dewalts, as Dr. Joe has said, really are the best imaginable gearbox that can be adopted for FIRST. They mate to everything, they're super light, easy to mount, have awesome three speed capability built in, and are tough as nails, even if you abuse them. However, the challenge is in making them. If you are willing to invest the planning time and schedule dedication to get everything fabricated and ordered for them, they will give you few hassles, and really make the design of the rest of the robot easier.

However, if you hack your way through the process, you'll wind up with a hacked piece of junk. Imagine that... If you put the proper effort into the Dewalts, they will return it a hundred-fold.

Re: White Paper Discuss: Nothing But Dewalts
 

id like to beg the differ on the modification of the sun gears. my team (1625) had 4 dewalts on the drive of this years robot. and all of the sun gears were modified on a manual lathe with a combination of HSS end mill and 1 carbide ream. and they never had any problems the whole season.

Re: White Paper Discuss: Nothing But Dewalts
 

Could we get drawings of these fixtures? that would be an awesome addition to the whitepaper.

Re: White Paper Discuss: Nothing But Dewalts
 

We have no drawings, but I will have students take some digital pictures of all the fixtures we use and upload them to the cd media section. I will post here when the students have done them.

The fixtures really help.

Re: White Paper Discuss: Nothing But Dewalts
 

I was wondering how the dewalts worked on the programing side of things? having the robots switch speeds during the matches, was that complicated for the programmers to solve? Or was it easy to program.

Re: White Paper Discuss: Nothing But Dewalts
 

I've read over the white paper and the various other threads on the subject with regards to slight modifications. What I hadn't noticed was if anyone had come up with a design or modification to allow these excellent transmissions to work with the Mini Bike (aka large) CIM.

If so, I'd like to hear more about it or discuss it.
It's something that might be worth pursuing.

Thanks

Re: White Paper Discuss: Nothing But Dewalts
 

Phalanx,

Yes we converted the big cim last year when the season was over, we built two of them and put them on a chassis.They were really slow. They would be good for an arm but they are really heavy. I would not use these motors in the DeWalt form, I guess I would not trust them, just my opinion.

Re: White Paper Discuss: Nothing But Dewalts
 

As Josh indicated - without attempting to modify the gearing in the dewalt - the big CIM ran pretty slow. Unless the application was appropriate, I wouldn't use them.
If they were adapted to the proper gear box they could work as well as the other size CIM. Although, it might be easier to drive through an external gear box, to get what you need out of them.
So, if you wanted a big heavy motor that would work all day long, without over heating - and you had the weight available - the big CIM's could probably be adapted.

Re: White Paper Discuss: Nothing But Dewalts
 

Team 33 used A big CIM with a dewalt for drive in 2006. Iirc, it worked out pretty well.

Re: White Paper Discuss: Nothing But Dewalts
 

I should have put this in my previous post, but alas hindsight is always 20/20.

I never had any intention of using the Dewalt transmission with the BIG CIM for a base drive. The thought was as others have pointed out, that perhaps it would be suitable for an arm or turret etc...

Odd are it might be, but it may not be worth it, there might be better choices.

Thanks for the feedback and exploring my thoughts.

Re: White Paper Discuss: Nothing But Dewalts
 

I have a couple quick Questions.

Has anyone had problems removing the chuck off the end of the drill?
And How did you end up getting it off?

We are having problems with it and we need some help!

Re: White Paper Discuss: Nothing But Dewalts
 

Yes, we had trouble. Ended up using heat and impulsive force; i.e., torch, punch, and hammer. That loosened the (left) threads so we could get the chuck off. The trick is using just enough heat and impulsive force to get the job done, and not enough to break things. We had a very experienced tech-ed teacher lead the students through the exercise.

Re: White Paper Discuss: Nothing But Dewalts
 

There is screw that must be undone that is inside the chuck. I believe that it is reverse threaded. To get the rest of the chuck off, we used a socket wrench with a long lever attached to it. To interface the wrench with the chuck we used a hex adapter (something that fits in the socket and is hex-shaped at the other end). The adapter also needs to fit into the chuck. Tighten the chuck around the adapter and use the wrench to carefully unscrew the chuck.
Hope that wasn't too confusing... ;)

Re: White Paper Discuss: Nothing But Dewalts
 

It is easier and cheaper to order individual parts as per the NBD White Papers.

Dewalt has a great website http://www.dewaltservicenet.com

And YES they can be shifted with a simple servo.