White Paper Discuss: Nothing But Dewalts

[tiffany34990]

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

thankies again

[bmusser1]

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.

[Joe Johnson]

Originally Posted by Joe P

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?

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.

[Max Lobovsky]

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

[Arefin Bari]

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.

[Joe P]

Originally Posted by Arefin Bari

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.

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.

[Joe P]

Originally Posted by Max Lobovsky

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

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

[meaubry]

Originally Posted by Max Lobovsky

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

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.

[Joe Johnson]

Originally Posted by meaubry

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.

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.

[Joe Johnson]

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.

[Stu Bloom]

Originally Posted by Joe Johnson

... 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....

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!!

I think I'll visit ebay!

[Joe P]

Originally Posted by Stu Bloom

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!!

I think I'll visit ebay!

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

[ajlapp]

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.

[jimfortytwo]

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.

[Stu Bloom]

Originally Posted by Joe P

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

Originally Posted by jimfortytwo

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.

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!!

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