36:1 - 24:1 Drill gearbox Conversion

I know quite a few people are doing this, and plenty of others are asking questions.
Can someone who's done it, and is yet to do another please take some photos and make a short 'how-to' guide.
A few people (myself included!) are confused about some of the details.

For instance what parts do you need?
What is being changed?
One thing that occurred to me is which stage are you actually changing? If the first then don't you need to change the pinion gear on the motor?
Can't imagine that would be easy without a gear puller and a press.

The first stage in metal gearboxes is often actually plastic, since it's under the least torque. (I think that's correct?) So would be nice to be able to swap them out.

Thanks!

I could do a step by step guide sort of thing as I got all the parts for it, but this is a plain swap from a 24:1 Gr02 setup to a 36:1 GR02 setup
Not sure if this is what you're asking for as the internals of any other motor gearbox might not match with the Gimson internals.
Will have a look at the makita motor gearbox I have and see what they're like

A few people have done conversions on their drill gearboxes with the spares from Gimson, but not on GR's themselves.
This is what intrigues me, since if a straight swap is possible it could be very useful to a lot of people, especially since one of the stages in many metal gearboxes is infact plastic.

For starters, you should always swap the plastic gears out! They'll break before long and the resulting plastic teeth mess will clog up the rest of the gearbox (we discovered this at our first event) and more or less render it hopeless until completely stripped of all grease. I believe the cheapy drills from Argos are currently entirely metal gears, and we got lucky at Homebase a while ago but having bought another more recently they have returned to plastic first stage. If you don't happen to have enough metal gears to swap them, Gimson sell them, you want the 18T ones if you're staying 36:1.

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For the conversion of a standard drill you need:
A 15T carrier plate - http://www.gimsonrobotics.co.uk/spare-g ... _GR02.html

And a set of 15T gears per drill - http://www.gimsonrobotics.co.uk/spare-p ... _GR02.html

You may also want to make life easier on yourself and just get a new motor with the 15T pinion gear already attached so that you don't have to attempt pressing your own on if you don't have the kit to do so. This is what we did, and it saved a lot of headaches.

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Loosen the grubscrews in the front of the gearbox a little bit so that they don't force the whole gear setup upwards. Remove the motor and open up the gearbox of the old drill. Take the first stage of gears out, they'll be 18T so they're spares for the second stage should you need them, though if they're plastic they'll be eaten by the torque in the second stage in no time.

Take out the existing carrier plate. This plate only works for 36:1 setups, so keep it as a spare for your other unchanged gearboxes.

Put in the new 15T carrier plate from Gimson. It will take a bit of fiddling to seat it. I'd suggest putting some fresh grease on the underside, though not too much as on this small scale too much can cause resistance and run your motor harder than necessary.

Place the new 15T Gimson gears on the 3 pins of the new carrier plate, again this takes a bit of fiddling to seat them, and a bit of grease on this side is good as they're completely fresh parts.

If you have a motor with the new 15T pinion (they come with 9T pinions) on, either bought that way from Gimson or pressed on (if pressed bring the front edge of it flush to the end of the motor shaft, as per Gimson's images), grab it now. Move the plastic end plate that joins the gearbox and motor onto the new motor/put it back on the original, making sure to tighten the two screws, as they're often loose from the manufacturer and can loosen in combat.

At this stage you need the metal plate that came with the original drill that goes between the innards of the gearbox (sits over the new 15T gears) and the plastic plate that holds the motor onto the gearbox. They're like a big thin washer. Often the hole in the centre is only big enough to pass a 9T pinion. I don't know where you can purchase ones with a larger enough hole to pass the new 15T pinion. We have several of both types, as these cheap drills seem to come with both kinds. Ask around if you don't have the right thing, or perhaps someone could make up a load for our use. If you have a decent drill you could drill it out fairly easily.

Place the big washer whatsit over the gears, and then position your new motor into the gearbox. You have to line up the little nob that is on the plastic casing of the gearbox with the hole/notch in the plastic plate holding the motor, and of course seat the motor pinion between the gears in the end of the gearbox at the same time. Bit of grease here is good, not a lot, though, none if you don't think it needs it. Getting the motor back on and in can be fiddly but if you have done it right turning everything around a little bit as you put it in should seat it.

Bolt up the gearbox again and tighten the grubscrews once more. I'd suggest running it on a lower voltage battery than the motor, at least initially, to run the gearbox and motor in. If there are any major vibrations or audible clunks as the gearbox goes round, open her up and see if you can see any issues, like debris. A bit of vibration is to be expected from these, especially from the bearings, they're fairly nasty. Leave it running in both directions for 5-10 minutes, this smoothes out the new gearbox and can drop your current draw hugely, and if nothing sounds or feels wrong, you've converted your 36:1 drill to a 24:1 drill.

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If I have missed anything let me know. I will happily make a video of this, the mess from doing this myself is still on the table!

That's excellent Ellis! Thank you very much. Didn't happen to take photos as your went did you?

Good point on buying motors with the 15t Pinion. Means I can also get 24v and non-advanced magnets.

I didn't, no, but if I take one of the gearboxes apart again (we have to strip down the robot at least once more before the champs so I can do it then) I'll make a video/take pics then. In the meantime ask if you have any questions, the past year of fighting our own motors has taught us a lot about them!

Also yes, the higher the voltage you run the more efficient and the greater torque. Though be careful with the 24v ones, I may be wrong but I think I have read something about them being the wrong shape to fit into a gearbox off the bat. That may have been GR02 specific, I'm not sure. The 12v and 18v models go in like the originals.

Also, you might want to think about doing something with the pins in the output shaft if youve got it apart. People have used super glue i think to give them a little more security as they can work loose.

I'm hoping the shaft pins are going to up be up to it, judging from our experience and yours. We overvolted 12v motors by a lot, so they produced a ton of torque, and you overvolted by less but you had motors with more torque to start with (18v). The end result is probably about the same, and the pins can't take it.

Point is if you're running a motor at its nominal voltage I imagine you're safe. The most effective way to just bypass the issue would be to weld the back side of the pins onto the plate, so that they can't loosen. I don't think a bit of superglue is going to do enough to be worth it. Plus you'd have to clean everything back to bare metal, a big overhaul, I doubt any glue would do much with the parts even remotely greasy.

What grease do people use? Can't be too thick, can't be too thin, needs to be juuuuuust right.
I wonder what Ewan uses in his gearboxes before he ships.

We're using this stuff:

http://www.commaoil.com/img/photos/p...large/1254.jpg

Seems to work well.

Cheers!

I've always used copper grease. Two reasons,

1) It's good at high temperature applications and if your gearboxes get stressed that could be the case
2) I always have it in the garage for working on the car

That CV Lithium grease Ellis posted can be bought at your local Halfords for a few quid. Got myself a tub of it the other day, don't see me running out for a few years yet!

I believe Halfords is where we got ours. :proud:

i use lithium based grease as well. but regarding the gearboxes im doing it but i would be cautious about it, there will be a load of more strain on the motor. Wouldn't suggest anyone with 2 motors to do it, and those with 4 wheel drive should still be careful about it.

I plan to test them at many events before I go to the champs, as I can imagine motors going up at the champs so I want to see if its worth it before actually competing with it. And those who are doing it, good luck! would be cool to see how it goes though. But i wouldn't suggest blocking tho motor vents like some people do, as i think that would be the last straw for the motors. And heat sinks would probably go down well.

I don't think it's going to be an issue. Our robot is in no way struggling to move around, it's virtually the same as it was before in terms of grunt, which leads me to believe the motors can happily handle it.

Two-speed cordless drills with 550 motors go to at least 24:1 as they often have a 900rpm option, and they're commercially designed to take the stresses of years of drilling. Plus many people use the 16:1 Banebots gearboxes without issue, which is even more extreme.

I'm open to it being a problem but I don't think it will be.

Only just remembered that the old Kaizer Mk.3 version ran 24:1 gearboxes onto 100mm wheels at Rebel Robots and the UK champs in 2009. It flew all over the place, and would powerslide nicely in the larger Rebel Robots arena. Shame it wasn't the easiest to control. The motors were 16.8V ones running on 24V and we never had a problem.

http://www.youtube.com/watch?v=y1HuBxWVCoI
http://www.youtube.com/watch?v=28_rBS3jy0o
http://www.youtube.com/watch?v=_vbu4v22xrA

Had a go at the makita motors I have on Liftoff and took the gearbox apart - it does not look anything like the GR02 gearbox though!

Its got 3 stages instead of 2, and the ratio is 48:1! No wonder why its so slow... :| Apart from that compared to the GR02 both motor and gearbox are enormous and weigh a tonne!!

I was reading through this and it struck me...rather than mess about with stripping down old stuff would it just be easier to spend thirty quid on some fresh Gimson's?

yes, but it would be expensive. £120 gimpsons, or £40 for the parts to change 4 motors. easy choice for me?

Why £120, wouldn't two motors be enough?

Plus some people have built their robots around existing drill motor gearboxes, the Gimson's, although with better mounting options, are quite different.

Yeah never thought about people with 4 or 6 motors! lol

And yeah see what you mean about people with existing setups just after replacing their internals.

I don't understand the reasoning behind putting too much motors in the machine...in the end I think its useless having more power than you can transmit to the wheels.

The real issue would be the grip/friction at the wheels and motors powerful enough not to stall. But I stand to be corrected :wink:

I admit that there have been times I've seen 6wd robot designs and thought I wonder if it would just wheel spin all the time?.

Nope :)
Ricochet drives nicely, fast, powerful and no wheel spin at all, and it has 6 motors.

Some robots have awesome drive with just 2 550 motors, it's all about how you put the power down and how you get it to the motors.
Having 4 motors and gearboxes is just an easy and cheap way of getting 4WD since setting up pulleys, belts and passive axles can be an expensive and time consuming process.
As for 6 motors though I can see it just being a hindrance since it'll create additional unwanted friction when turning.