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)...