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Unread 03-07-2003, 14:28
Andrew Andrew is offline
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32DP gears (odd sizes)

I spent many hours looking over my usual sources and could not find this part. Anyone out there have better sources.

I need a 32DP, 20 degree PA, 13 tooth gear.

I had no luck with Stock Drive, PIC, Emerson, Boston Gear.

Anyone have a better source? Is this a part that does not exist?
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Unread 03-07-2003, 15:25
sanddrag sanddrag is offline
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MSC has a 12 and 14 in plastic. Berg has them in aluminum and stainless steel. The 14 you can get with a clamping hub. Mcmaster has 12 and 14 in brass.

As for the 13T, Check with Rino Mechanical and www.pic-design.com

Hope this helps.
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Unread 03-07-2003, 15:52
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Pinion Wire may work...

I don't know your application, but Stock Drive Products sells steel and brass pionion wire with 13T, 20 deg PA, 32 DP. 13 Teeth are not too easy to hold in a lathe, but you can usually find a collet to hold them. Even a 4 jaw chuck can work if you don't mind crushing some of your gear stock (and are willing to fuss around a bit to get things to run true).

Part number: A 1B 9-Y32013 (brass) or A 1C 9-Y32013 (steel).

If these won't work you can always have them cut or burned.

Depending on the quantity and what ever else you need done (hubs, keyways, etc.), you should be able to get them cut or burned for about $40-50 each.

Let me know if you need help finding a source to make them for you.


Joe J.
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Unread 03-07-2003, 17:13
Andrew Andrew is offline
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Thanks, this looks exactly like what I'm looking for.

Just a question, what is the difference between "pinion wire" and "spur gear stock"?

Application: As long as the fab rules don't change dramatically and the kit motors stay the same, we may choose to design a planetary stage for the FP motor.

The pinion is 19T (last year). So, with a 45T ring gear, we would need four planets of 13T.

This would give a GR of 64/19. With the FP NL speed of 15000 rpm, the first stage NL speed would be 4453 rpm.

This is very similar to the Chip NL speed of 5500 rpm and the drill + first stage NL speed of 19670 rpm / 4 = 4918 rpm.
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Unread 04-07-2003, 09:46
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Whoa there, El Presidente...

Andrew,

Go slow. You are about to make a mistake I learned the hard way in my day job about 10 years ago.

Not just any gear sets will work out for a planetary gearbox.

While you seem to have the ratios and the numbers of teeth all worked out, planetary gears have special constraints. Specifically, you are between a rock and a hard place in terms of gear centers. By this I mean that you have nowhere to go if you need a little more backlash to make your gearbox run better -- increasing backlash on the sun/planet jams the planets into the ring.

AND... ... I don't know if the Fisher-Price pinion has been enlarged (I think I recall that it has, but old age has adled my brain ;-) If it has, this is typically not a problem with normal gear engagement because you could just increase the center distance and off you go, but planetary gearsets are another matter.

Also, even if you don't have this enlargement to deal with, you may be in trouble anyway. Basically, planetary gears require a higher AGMA quality number to work AND (finally getting to one of your questions) the AGMA quality of the "pinion wire" from stock drive is not as high as their "spur gear stock"

I am not 100% sure, but from what I see from looking at the parts, the "pinion wire" seems to be made by the mile using some kind of extrustion process while the "spur gear stock" looks like it is hobbed in 6 or 8 inch lengths. This is why the spur gear stock has a shank and a center hole in the opposite end and the pinion wire has only saw marks on its ends. This is also why it is harder to work with pinion wire (i.e. to chuck in a lathe) than the spur gear stock.

Anyway... ...I recommend that you go slow on this -- get some samples and try things out before you plan on building 10 or 100,000 more like it.

I have another question as well. Why a planetary stage? While I love planetary gearsets and I hate myself for talking the world out of making more of them, I wonder if a standard gear set may give you what you need without the bother. Do you need the package space? Do you need to have the ring slip? Are you making a shifter? If not, perhaps there are easier solutions.

Think about it.

Joe J.

P.S. Backlash is almost always your friend in FIRST gearboxes. I would design in TONS of backlash. Typically, I can live with the lower contact ratio. the slightly weaker teeth, and the possible extra noise. I typically cannot live with the inefficiency of gears jamming together. For what it's worth. JJ

P.P.S. If the rules don't change and you want a planetary gearset, I say, buy it don't make it. The Fisher Price motors fit on the planetary gearboxes from the drills two years ago. I think you can buy the gearboxes for cheaper than you can buy the stuff from Stock Drive products. All you would have to do is buy or make the gear that is pressed on the standard drill motor (again, I have fould that the gear from the drill service center is often cheaper than the same gear from Stock Drive Products).

Good luck. JJ

Last edited by Joe Johnson : 04-07-2003 at 09:54.
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Unread 04-07-2003, 11:31
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Joe,
I appreciate your comments.

Part of the reason for designing the planetary stage is to flag all the issues that you raised and work through them. Both conceptually and practically.

Two years ago, we designed and built our own planetary stage using small parts gears (actually Boston Gears). We used all spur gear stock, so perhaps the quality of the gears saved us from difficulties.

When you say "enlarged," does that mean the teeth tip are a little longer than normal?

My second choice for this project was to pull the FP gear off and replace it with another pinion. I was thinking of using the final stage in the new drill motor GB. Bosch has already done the design work there.

I really appreciate the advice and cautions. The only thing better than learning from your mistakes is to learn from someone else's.

Plan C, of course, is to go with a straight gear train from the FP pinion.

As to what we're contemplating...
Last year, we took the drill motor and its first stage and made a housing and a new output shaft. The mounting configuration, space claim, and shaft configuration matches the Chiphua. We designed a GB which got us to our final gear ratio. We then inserted drills and chips into our four identical GBs. Well, if four worked, why not six?
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Unread 04-07-2003, 12:02
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Enlarged...

For gears with small numbers of teeth, you can get thinner teeth than you would like. In particular, the teeth are weaker than the gear it is mating with.

We want to make the teeth on the smaller gear stronger.

There are a number of strategies but they generally involve 2 methods:

1) leaving the larger gear alone and increasing the center distance over the standard distance. The smaller gear then grows ("enlarges") to fill the extra backlash. The how this is done varies, but typically both the OD and the Root Dia. grow.

2) leaving the gears on the same standard center distance and simultaneouly thinning the teeth on the large gear and thickenning the teeth on the smaller gear.

Obviously #2 won't work well if both gears are the same size (one gets stronger, one gets weaker).

Sometimes aon planetary gearsystems they drop a tooth from the planets and add a tooth to the sun and the add 2 or even 3 teeth to the ring gear. This adds gaps that give the gears room to be enlarged.

FYI.

Joe J.
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Unread 04-07-2003, 15:18
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Ken Patton Ken Patton is offline
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new FP pinion

We have in 2 of the last 3 years removed the pinion from the FP motor and replaced it with our own metric gear. Its pretty easy to do as long as you take care not to damage the shaft. We never had one fail. I know team 71 has done something similar, because in 2002 (I think? maybe 2001...) they lent us their very cool pinion puller fixture which made precise disassembly/assembly in the pits an easy thing to do.

That is one problem with swapping thw gear out - if you burn up an FP motor, you need to have a spare with the right gear on it, or be ready to modify a borrowed motor in the pits.

As to going to extremes to use the drill gearbox - I question that approach. The drill gearbox is not as efficient as a simple spur geartrain. It is pretty compact, though... I guess it depends on your objectives.

Ken
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Unread 04-07-2003, 18:34
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Joe,
Thanks for the info. I had seen in the drill motor GB that the number of teeth and (I think) the center distances did not match the theoretical values. I had always wondered about that.

Quote:
As to going to extremes to use the drill gearbox - I question that approach. The drill gearbox is not as efficient as a simple spur geartrain. It is pretty compact, though... I guess it depends on your objectives.
Ken,
One reason that we abandoned stages 2 and 3 of the drill motor GB was efficiency.

Why would we go with one planetary stage on the FP?
1. It's more expensive
2. It will take more time to machine the precision parts
3. It's less efficient
4. We're restricted to fewer options at gear ratio
5. It will require much more engineering time
6. It might not work at all

Umm...not looking good so far...

7. It will look so darn cool!
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Unread 15-07-2003, 23:34
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Re: new FP pinion

Quote:
Originally posted by Ken Patton


That is one problem with swapping thw gear out - if you burn up an FP motor, you need to have a spare with the right gear on it, or be ready to modify a borrowed motor in the pits.

Ken
It's not really that hard. You can custom fabricate a small device that latches onto the motor, and you just smack it with a hammer a few times and out pops the gear. All it needs is 2 machined plates that are about 3/8 in thick. In fact, I did this process today in my garage with a FP motor. The only thing you have to do is have the gear already cut with the pressable hole, which is
.1192 in for the FP motor (standard drill bit size). Then all you do is tap it on (more like smack it on) with a hammer, using the same machined plates. The only difference is that I didn't put a gear onto this motor, I put on it a block of aluminum. (What?! Just some innocent fun.) All done in about 5 minutes. All you need: new motor, already modified gear, hammer, special plates. If you want, I can post the inventor files of these plates.
In fact, I will, but once I find them.
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Unread 30-07-2003, 23:10
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Dennis and I are firm believers in the stock Bosch trans. We modified how the shifting mechanism operates, but the planetary is stock Bosch. Frankly, we are suprised by the durability those little gear boxes display. As far as efficientcy, Lets just say Team 27 has some respect in Auton mode. Our drive doesn't seem to kill batteries and is as fast as most other drivetrain designs. The trans pops out of the chasis in less than 2 min, and is very easy to work on, while not hogging up a lot of space in the chasis. They are also lightweigth at 7.8 pounds each. That's an Atwood and a Bosch motor, planetary section, and the air cylinder.

I for one don't want to reinvent the wheel every year. I would rather use something off the shelf with some minor modifications than have to start froim scratch. I don't see why you couldn't change the pinion on an FP to work with a Bosch trans. Although Ken is correct, putting on a special gear means preparing extras for competition.
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Unread 11-04-2004, 01:24
sanddrag sanddrag is offline
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Re: 32DP gears (odd sizes)

Quote:
Originally Posted by Andrew
I spent many hours looking over my usual sources and could not find this part. Anyone out there have better sources.

I need a 32DP, 20 degree PA, 13 tooth gear.

I had no luck with Stock Drive, PIC, Emerson, Boston Gear.

Anyone have a better source? Is this a part that does not exist?
Sorry to bring up an old thread but if by chance anyone stumbles upon this and is still looking for that gear, here it is http://www2.towerhobbies.com/cgi-bin...?&I=LXEW98&P=7 Sorry I didn't find this thread sooner because I knew about that gear all along.
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