Chief Delphi - White Paper Discuss: Nothing But Dewalts

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Re: White Paper Discuss: Nothing But Dewalts

Quote:

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.

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

Quote:

Originally Posted by pakrat

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

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

I have gotten this question via e-mail:

Quote:

We're planning on adopting this design using 4 CIMS and 4 Dewalts to drive our machine this year. But I don't quite understand how pressing the Top Hat Carrier assembly to the shaft of the CIM shaft keeps it from spinning free without the use of a keyway.

Here is my reply:

Quote:

Talking to an engineer friend of mine (Artur O. from team #469), he told me that I have voilated all the rules with the Chiaphua-Dewalt design:

A press fit with so thin a metal ring left below the root of the tooth,
In fact, I voilated the rule of thumb that you should have at least 1 tooth thickness below the root even without the added stress of a press fit,
a first order stess calculation shows the part should break, and so on
etc.

BUT... ...the things work. That is all I have to say in my defense. They work and they work great.

In engineering, many of our rules of thumb are conservative. Our team has had A LOT of hard driving on our transmissions. We have had no failures. I feel comfortable recommending it to others.

Now to your specific question: the part is a press fit. There is no room for a keyway in the root diameter of the gear that presses on the shaft -- though, now that I think of it, it suppose it is possible that you could put a keyway in the plastic tophat part.

But, in actual fact, we have had good experience with just using the press fit.

You need to be very careful to make the hole in the gear "to print" As I recall, .312+0-.0005 and the shaft itself is .313 so this gives a significant interferance fit.

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

Quote:

Originally Posted by ajlapp

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

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

Quote:

Originally Posted by Derek Bessette

What modifications are required to the fisher price pinion?

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!

Quote:

Originally Posted by Derek Bessette

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.

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

Quote:

Originally Posted by Max Lobovsky

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