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planetary gearbox questions


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Glen
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planetary gearbox questions

This one might get a little tricky,

planning on remaking the 2 speed dewalt gearboxes that have 3 planetary stages in them. one high speed gear and one low gear.

what im wanting to do is basically remove the low gear from it to make it smaller/lighter/more efficient etc and im trying to work out which stage it is that i have to remove. i think i know but want to run it by everyone first..



this is the first two stages (with the first gear carrier removed) in low gear. so all the planetary stages are working to add to the gear ratio.

now when you put it in high speed this is what happens -




the second stage has the sun planet and ring gear all locked together and rotate as one piece, so its my understanding that this stage is now providing no reduction?

so in my plans im going to remove the second stage from the gearbox and run the first stage into the 3rd to have the high gear constantly engaged.

thoughts, advice, questions ? cheers
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Post Tue Jan 06, 2009 1:30 pm 
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timmeh
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Yes should work.

Iv done the same thing with some ryobies you remove the middle gears and the first and last stage magicly fit together.
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Post Tue Jan 06, 2009 1:43 pm 
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Nick
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If you are going to take out stage 2, the sun gear on the first carrier will have to match up with planetary gears of stage 3. if the stage 1 & 2 sun gears are the same, the project is feasible.

Are you planning to replace the whole case of the gearbox?

Post Tue Jan 06, 2009 1:52 pm 
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Glen
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yep well the 2nd and 1st gear carriers are identical except one has 2mm pins the other has 3mm ones. so the plan is to retain the 2nd and 3rd stage but drill the first stage gears to fit.

yeah planning to make a solid casing and remaking the last ouput stage to have a shaft instead of a socket so itll basically be this with a dewalt on the end - http://www.robotmarketplace.com/products/0-PIRGB1.html
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Post Tue Jan 06, 2009 2:38 pm 
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Nick
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Sounds like quite a bit of work, but the results could be amazing Smile You need to take care sizing the holes in the gears - drilling them slightly under sized and reaming them out in the mill will give the best results.

I have not seen the output plate from a Dewalt, but it could be difficult converting it to a plate + integrated axle.

Post Tue Jan 06, 2009 8:19 pm 
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Glen
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just down to cadding it now but it looks at this rate like itll be a bit lighter then the entire setup i have now even tho its all ali and a heck of a lot narrower

this is the output plate - its just the same as the drills but with a shorter end shaft and the X spline broached in the cneter. so making it solid shouldnt be too much of an issue provided the holes for the pins go in the right place.



not sure about how to drill the gears though. seems like clamping them in the lathe or mill will damage them badly
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Post Tue Jan 06, 2009 8:56 pm 
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Nick
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That end plate has casting marks all over it - you can make your replacement thinner if you are going to lathe it from bar stock. Have a thought about making a 4130 axle and TIG welding a plate to the end of it - could be much faster than lathing down a large bar

You will need to be very precise with placing the pins - get it wrong and the gearbox will bind up. I think its possible to mathematically work out the pin placement and then either a rotary table or a DRO will let you re-create it

Don't worry about drilling the gears out, I solved all those problems when I modded the Banebots gearboxes - PM me when you need the details and photos.

Post Tue Jan 06, 2009 9:11 pm 
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Valen
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could you post it here? inquiring minds want to know ;->

we have a rotary table if you need.
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Post Wed Jan 07, 2009 10:28 am 
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Nick
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I published the info in a Servo magazine article last year - I will email the word doco with some updates. It relates to the Banebots 42mm motors but the techniques are basically the same for all small planetary gearboxes.

Post Wed Jan 07, 2009 10:43 am 
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Glen
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if i could grab that too would be appreciated Very Happy
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Post Wed Jan 07, 2009 11:24 am 
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