Compact gearbox for the 22
 

I've recently bought a second hand 22-despite people warning me about it being hard to set up in mid-motor configuration.
What I did notice was that the motor was a lot more forward than the norm, which might explain the aformentioned.

So I figured it might be worth messing about a bit with the weight-distribution.
Hence the idea to make a more compact gear-box as a means of achieving this, without having to resort to a radical redesign of the entire car.

The design :

http://i131.photobucket.com/albums/p...ps37f30a3e.jpg

The motor is +/- 15mm more rearward; as an unfortunate side-effect, it’s also +/-8mm higher,
so my idea might actually have an adverse effect on handling.

So far, I’ve got it 3d-printed, (printed with heated filament wire ) Helas the quality of the print is so poor it barely allows me to check my dimensions ….

http://i131.photobucket.com/albums/p...psb1a55e43.jpg
I’ve requested prices to get a more decent print, but I think it’s going to cost me an arm and a leg..

If anybody’s got any comments on the idea itself or how to get a decent quality print, I’ll be glad to listen

Steven

I think you have the right idea. I fliped the rear arms around on mine to move the wheels forward to a normal length and more rear weight, but I think you're on to something a bit better. I don't think that having the motor a bit higher will have a big negative affect, I think moving it back will far out weigh the high CG

have you tried atomic carbon on here for 3d printing

Not yet, it's "old-timer" isn't it - would he be willing to help for a fee ?
He himself is selling the tardis but it's worth a PM of course

I'm not sure I'd be keen on 8mm higher!

nows there is nice idea. surely with new motor plate or something, you could place the motor lower?

Have you thought about having it CNC'd from Delrin at all ? Not sure if that might be cheaper, plus if you can get more people wanting one you could obviously do this on bulk = bringing unit cost down ?

Just throwing the idea in.


PS - Bloomfield seems to make the mid-motor config work, and work well

Sure, i've thought of having it CNC'ed but the CNC time does't come cheap - I now have a quote for around 86 pounds - printed in a mechanically resilient material ; if I should find a mechanist wiling to do it for about that price , I'd be happy

My driving skills aren't exactly at the Bloomfield- end of the spectrum lol

If you ask nice though he may share his setup for you :)

ouch £86 ! Worse thing is i think the delrin doesnt cost that much material wise...its probably only going to be about 5% of the cost i guess.

Hope you do get what you want done though

£86 sounds a bargin to me, I'd be very suprised if you get even remotely close to that for a one of machined gear box. Unless some one is doing it for spending money of course.

Cool project! :thumbsup: 3D printing will do very nicely, both in strength and accuracy. The FDM printed sample you have is not the neatest ever but does allow you to check if everything fits and 'works.'

As you're messing around with gear meshes - plus a part that (even if it doesn't hold the shock tower or turnbuckle joints) is exposed to quite a few stresses, I would go for a stronger material - and an accurate one at that. CNC Machining is indeed quite expensive - and in fact, may be unnecessary:

Option 1: Have the parts printed in a durable printing material (Nylon printed in an 'SLS' printer for example) - I predict that would set you back 30-40 euros and is just about as strong as nylon of the same blend when moulded :) It is also very accurate. The only potential problem is that the material is slightly porous, so it might not repell all the dust and dirt. This though it easily solved by coating the thing on the outside with paint or glue.

Option 2: Have the casings printed in an extremely detailed and smooth material - it will look moulded and smooth as silk! That's a good thing, because then you can make a silicon mould from these parts and cast (or vacuum mould) parts in these silicon moulds and resell them :thumbsup: It will be more expensive for a single set, but if you do 10 or 20 sets it's already money well spent. A downside to this is that any mods/customizations along the way will have to pay themselves back.

I work at a small company nowadays that does research on polymers and 3D printing, so if you are looking for more information, help finding the right material(s) or even refer you to contacts in the printing business to get the parts made, don't hesitate to PM me :)

Edit: Am I seeing correctly that the front gearbox mounts are the limiting factor to lowering the motor any further? If so, perhaps it's an option to entirely skip these mountings, incorporate TLR4162 (the inboard motor guard) into the gearbox housing and use the chassis holes for that part as the front mounts? Or the holes beside the front suspension hanger of the rear suspension that are unused in the mid-motor setting? :confused: It requires some re-thinking on the mountings of course, but if successful any concerns of adverse handling effects should be off the table :)

Hi,
you might want to check out shapeways.com . It's a company that does 3d printing (SLS) for "normal" people. They are based in the Netherlands. The prize for "strong + flexible plastic" (PA 2200) is $1,40 per cm³ (white).

I did a gearbox for my Academy GV2 mid-motor conversion, because I wanted an option to run 3 or 4 gears. Here is what my cad drawing and the final printout looked like:
http://www.offroad-cult.org/Board/at...1_getriebe.jpg

http://www.offroad-cult.org/Board/at...0_sany0844.jpg

My gear box has a total volume of about 20cm³, shipping was $9,50 so you can do the math (~£25). I don't think you can get it cheaper than that.
You might want to optimize material thickness on your model though to reduce costs. In addition to that, they have a handling fee for each part, so what I did for my three parts (the small one in the picture has nothing to do with the gear box) I connected them with a small link, so the whole assembly counts as one part.
Accuracy was fine, even the gear mesh, holes and fittings tend to be on the smaller side, which I prefer anyways.

Andi

3d printing
 

Hi Andy,

Definitely worth looking into-a company in the Netherlands would suit me very well; I'm Belgian:)
Nice lokking design BTW.

In the meantime I've had offers of help or valuable advice on the design from other forum-members (from, among others,Paul and Marc) all very much appreciated.

For the moment I'm making small mods (read : a complete overhaul :)) on the design and we should be ready for printing.

Someone suggested some more mods for the front of the car I'll be lokking into after that.

In the meantime I've run my other 22, build as a RM, for the first time indoor : against all expectations, it went really well :woot:

Grtz

Steven

Great idea! This was always a problem with the 22, the motor was so far away from the driveshafts in mid configuration! Good to hear you're making this, bet it will make a huge difference in how the car drives. 8mm taller is NO problem in my opinion, after all you've got heavy big bore shocks on all corners, adding 8mm onto the central positioned gearbox won't make that much difference in comparison.

Good work :thumbsup:

After some serious rework it should be ready for printing now:

http://i131.photobucket.com/albums/p...ps36ededf9.jpg

http://i131.photobucket.com/albums/p...ps4d9f80f3.jpg

Grtz

Steven

Are you planning to sell these to fellow ooplers with 22's ? paypal waiting :thumbsup:

Sure, if anyone should see the benefits of the design.

But first, I'd like to see if everything fits as it should.

From what I've gathered so far, 3d printing in a useable material doesn't come cheap-even if I sold the part at cost (wich I'd more then willing to do) you'd be paying maybe tenfold of the original Losi part...

In any case, I'll keep you posted

Steven

Wouldn't it be more cost-effective to adapt the hobao H2 gearbox to your TLR22?

I do like your work though: hope to see it some time in real life. Where do you run?

Why is having the motor positioned further from driveshafts a problem?

Lifting nearly 10% weight of a vehicle by 8mm won't cause any issues? really?

Maybe it would, but designing is half the fun.

I don't think you'd be willing to take the ferry to see it for real; I'm Belgian :lol:

Steven

BTW : I'm pretty sure Mr. Chimp might have a valid point, this is just me tinkering and in no way intended as THE answer to potential set-up issues

First trial fitting with the new print :

*The gear mesh seems fine
*Just one small design oversight that required some slight dremeling
*Printing tolerances well within the advertised limits, a little bit of hand fitting required but nothing major

http://i131.photobucket.com/albums/p...psf32b8753.jpg

They did a pretty quick job with the printing. It looks very neat! :thumbsup: It does look very strange to see the motor mount so high up, but I guess if CoG is an issue you could stick a slab of lead underneath :lol: It'd also help to put the weight bias further to the rear probably, and there's now room underneith the motor to play with something like that.

I'm really looking forward to seeing this box in action!

I fully agree Steven, but being greedy I try to make my designs using of-the-shelve parts (preferably my own shelves)
Why a ferry? Last time I checked Mechelen was still in belgium ;)

As far as I know, we have different types of gearboxes. But my mind is always bothered by this question. How does the car gearboxes works? Will you please give me some specific details of what are the functions of each gearboxes.

Have you tried it yet?
 

Great stuff i hope it works i loved my 22 but couldnt just control it as a learner,
And got sick of being told to get rid, the quality of the car is great, it would do the car justice if you can pull it off best of luck :)

That looks great, its really cool to see people trying more radical mods like this with 3D printing :D

Let me just say that I am quite new at RC racing, but part of me wonders if with this admittedly incredibly cool part you are simply swapping one issue for another. The much higher motor mounting position could cause a number of other issues.

Now let me ask something that to some may be obvious, but isn't to me. Why would this compact gearbox be better than the Cream Extreme RC rear weight or even the mid-motor rear weight kit? Seems to me like the weights allow you to move the weight balance rearwards without increasing the CG... But as I said, I may be missing something super obvious somewhere.

8mm higher motor offers some intersting options to put in the speedo and battery. Looks great! 8mm higher motor is much weight but looking at s ome rear weight kits and alloy gear cases they to the same. Maybe 4mm would be enough though :) .. want wait to read the first driving report.

:thumbsup:

Is it possible to get the file? A friend has a printer but i have no CAD skill:( Thanks!

It's too late now but if you redesign this transmission case in the future I have some suggestions. The problem with the 22 isn't that the motor is too far forward, it is that the rear arms sweep back too much and the diff is too far back. If you look at some of the other mid motor cars the motor is placed right in front of the rear suspension block (just like the 22) but on the 22 the diff is stretched out so the outdrives come out at the rear of the arm. The ideal setup would be to switch the arms left and right (sweeping forward) and design a compact transmission that would keep the motor low and in front of the suspension block, with the diff moved forward to reduce driveshaft bind caused by flipping the arms. I believe this is the setup used by the VEGA kits, although they are a little pricey. If someone were to make a case such as that that bolted straight on, I'd be very interested in buying one.