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Mechanical tech This is for the mechanical parts of a model. Gear reductions, Axles, Transmissions, General drive line


View Poll Results: Would you buy this if it went into production?
Yes I would buy a metal version 11 32.35%
Yes, but I would like a cheaper plastic version 16 47.06%
No, there are better options out there 7 20.59%
Voters: 34. You may not vote on this poll

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  #1  
Old 06-02-2016, 06:52 AM
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Default Tamiya bolt on reduction gear

Hi guys. Some of you maybe read a thread about my 8x8 truck, and this thread is a part of why I didnt update my 8x8 for some time.

So the story is simple. Since I wanted my 8x8 to drive as soon as possible, I decided you buy tamiya 3 speed gearbox, and just connect it to my transfer case and drive. I will update 8x8 thread with more details about that, and problems with that idea, and I will put here a solution.

I found that the main problem with tamiya 3 speed gearbox, used on my hilux, my 8x8, and on 4x2 and 6x4 trucks, is the speed. This trucks are just too fast to be scale. I googled and I see many people swap motors, others put brushless in, so they cant use MFC esc if they bought it earlier. Than other go as far as removing 3speed gearbox, and just puting geared motor in. And then buy new sound system. As I see it, many spend to much, change to much, and I cant see why??

I started modeling reduction gear to fit on my 8x8 tamiya 3 speed gearbox to slow it down. And after first prototype test, I stopped working on 8x8, and designed complete kit for tamiya trucks.

Here are few 3D photos.













I installed it on my 4x2, and started testing it. I just wanted to try 3D printed parts, and when I got the design right, make it all metal on CNC.






Fiting is fast and easy. Just remove 4 screws on the back of the gearbox, and remove prop shaft cup. Bolt the kit on with new longer bolts, and put a new shorter prop shaft. Thats it, 5min job. My truck is stock out of the box MAN 4x2. I just put 3S ESC in, and I use 3S lipo. Only reason for this is, I dont have 2S batteries at home.







Now the problem is, i guessed wrong, the part that it will brake soon as its 3D printed. IT DID NOT BRAKE. So I tried to push it harder, so it would brake. And I failed. Its still running.




This last photo was too heavy, susspension was on the limit, and truck pulled it like it was empty.
As I couldnt brake it, I made another kit for my friend so he can put it on his scania 6x4 with mfc. He likes to brake stuff, so I tought maybe he will do it. And he also failed, but we were amaized with the change this small kit did in transforming his mfc powered truck. And I dont know why tamiya didnt make it like this from factory as its super fun, and milion times better to drive. We will try to shoot a nice video to demonstrate how the truck work.

Let me know what do you guys think about this? Do you share my toughts about this speed problem on tamiya trucks.
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  #2  
Old 06-02-2016, 09:13 AM
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Default Re: Tamiya bolt on reduction gear

I like it! How much $$$?

Reg
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Old 06-02-2016, 09:25 AM
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Default Re: Tamiya bolt on reduction gear

Wow, I think your really onto something here and I'd be ready to sell these to every member on here. The aesthetics of your design are extremely nice but being a CNC programmer and job estimator I think they will cost a fortune to surface them out of metal. Most aftermarket 3d milled parts on the market could look a million times better if the mill step over was shorted and feed rates were reduced, but of course that costs more. My point is if someone is going to quickly 3d mill something and produce a bad finish (ex. the rc4wd Kenworth grills) you might as well just print it and sell it at a lower price point. At least the color blends in. Kudos to your ingenuity and Im very interested in seeing this evolve.
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Old 06-02-2016, 12:01 PM
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Default Re: Tamiya bolt on reduction gear

Thank you for replys. I would like to answer to you that this case design is only for 3D print version. Milling and 3D printing have 2 completly different aproach. So this is designed so I can get the best print result, and all these 3D sufraces are there for a reason, to be strong enough as the hold ballbearings and load of the shafts. So its more of the ratio for added material where its needed, and again not to much so I dont wait too long for it to print out. So its function over fashion
Milling version will have only streight cut gears, and much simpler case. But the gear ratio will stay the same.


I added a poll, maybe it could give us some results to point this the right way.

Last edited by Doggy; 06-02-2016 at 12:07 PM.
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  #5  
Old 06-02-2016, 02:10 PM
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Default Re: Tamiya bolt on reduction gear

Your idea looks very well thought out and looks promising. Are you aware PMD already has an add-on reduction box for the Tamiya trans? Installation, overall design and appearance is similar to yours.

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Old 06-02-2016, 03:08 PM
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Default Re: Tamiya bolt on reduction gear

Thnx, no I didnt find any other similar products. Please post links if there are alternatives.
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Old 06-02-2016, 03:35 PM
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Default Re: Tamiya bolt on reduction gear

Ok, I found this from PMD.
http://www.ebay.com/itm/New-PMD-4-1-...-/111861062944
It doesnt really look bolt on, and I guess this design use more space, so I couldnt put it on stock 4x2 without moving the stock battery out. Also I see its 4:1.

I forgot to write my reduction is 6.43/1, so its slower.
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Old 06-02-2016, 03:48 PM
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Default Re: Tamiya bolt on reduction gear

i use the carson 4:1 reduction gearbox, i think its abit to slow... been wanting a 3:1.
like this one... http://www.gardentrucking.com/detail...d#.V1CMk_mLSJA
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Old 06-02-2016, 05:34 PM
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Default Re: Tamiya bolt on reduction gear

Here is the GRU I use on one truck. Can't beat the price and I've pulled a lot of weight on a pull sled with it. I currently run a stock can for a good all around speed and go to a 55 turn for crawling/heavy hauling.

http://www3.towerhobbies.com/cgi-bin...?&I=LXVLE9&P=7

This is the best photo I have with it mounted.
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Old 06-02-2016, 10:38 PM
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Default Re: Tamiya bolt on reduction gear

Quote:
Originally Posted by Doggy View Post
Thnx, no I didnt find any other similar products. Please post links if there are alternatives.
PMD 4:1



Last edited by Claus; 06-02-2016 at 10:43 PM.
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  #11  
Old 06-02-2016, 11:24 PM
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Default Re: Tamiya bolt on reduction gear

Plastic might be a good alternative to the PMD one already out there. You mentioned 8x8 and for that you'd need front output also (and reduced) or a separate transfer case anyways. I haven't seen it by a US seller, but a longer output shaft can be made for the 3 speed. I think Willy (CustomRCModels) made them for himself? I think you'd be better off with an R2 IMHO. Freddy used axial transmissions as transfer cases and they were sweet at the time before there were so many options available to the hobby.
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Old 06-03-2016, 04:01 AM
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Default Re: Tamiya bolt on reduction gear

Claus that PMD looks good, and has a fair price for a metal version. Thats what I had in mind from the start, but didnt know where to find something like that.

So I guess a plastic verion, half the price would be a good deal?
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Old 06-03-2016, 04:20 AM
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Default Re: Tamiya bolt on reduction gear

as long as you can print it strong enough. ive had alot of printed parts look great
but snap,wobble. and just fail
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Old 06-03-2016, 04:35 AM
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Default Re: Tamiya bolt on reduction gear

My parts ar printed with 100% infill, so are as strong as material it self, and the design is what makes it strong not to snap or wobble. In this case, only thing that needs to be strong are the gears, and after testing them, only way they will fail is if they heat up too much. So they will melt before they snap. And I dont see how much you would have too pull for it to get worm enough to melt.
But I am waiting for a special more expensive material, designed for printing gears, so with that thing, it should be unbreakable. i will have to make few test videos asap.
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Old 06-03-2016, 10:40 AM
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Default Re: Tamiya bolt on reduction gear

Kind of getting off track here, but some of you mentioned using a transferase and running a driveshaft under the 3 speed. We all know there is not much room under that transmission and you have to lift it sky high, I have bought one of these aluminum transmission cases off eBay, they come in different colors and are one piece so the have to ears to screw them together. Maybe not the biggest help but when running a driveshaft under a 3 speed you need all the room you can get.

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Old 06-03-2016, 10:59 AM
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Default Re: Tamiya bolt on reduction gear

Yes thats offtopic, but maybe I open a new thread with a solution for that problem, as I would like to have on demand driven front axle. First I need to design new axle, and then find new route for the driveshaft, as I would like it all o stay stock.
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Old 06-03-2016, 08:11 PM
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Default Re: Tamiya bolt on reduction gear

The longer shaft (here) has the benefit of the output on the front of the tranny. It also has the drawback of having the output on the front of the tranny since it is already very tight in stock locations!
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Old 06-04-2016, 10:27 AM
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Default Re: Tamiya bolt on reduction gear

Quote:
Originally Posted by Doggy View Post
My parts ar printed with 100% infill, so are as strong as material it self, and the design is what makes it strong not to snap or wobble. In this case, only thing that needs to be strong are the gears, and after testing them, only way they will fail is if they heat up too much. So they will melt before they snap. And I dont see how much you would have too pull for it to get worm enough to melt.
But I am waiting for a special more expensive material, designed for printing gears, so with that thing, it should be unbreakable. i will have to make few test videos asap.
Hmm, printing gears no tanks unless they're printed on the highest quality professional printer in sintered metal . How are you keeping a tight bearing bore in that printed resolution ? How is it for longevity . IMHO, home printed parts are good for cosmetics , but are prone to failure doo to the porosity in the microscopic structure . Parts machined,injection molded and cast have a consistent grain structure which is paramount in the parts strength . Yes, it looks "strong" with all the bulk around the bearing journals, but is it ? A good well placed single weld bead is in most cases stronger then multiple layered poor weld beads .

In short , I applaud your effort for one self . I would consider a different approach of manufacturing if you plan to sell .
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Old 06-04-2016, 11:20 AM
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Default Re: Tamiya bolt on reduction gear

Well, I guess the best way to find out if they are strong enough is to test them?
Yes FDM technology has weak points, but if this gear with all its faults is good enough for 1/14 truck, then I dont see a problem.
I used the printer just to print the prototype, to see how it sits on the truck, and get correct dimensions I would later use on a mill. I didnt think it would be usable, as theory says that. But I was wrong. I also printed beadlock wheels for my 1/10 crawler, they also never failed, and I guess they were stressed even more.

But yes, when I finish a metal version, I will compare them and do more testing.
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Old 06-12-2016, 12:18 PM
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Post Re: Tamiya bolt on reduction gear

Hello all,
I have to give good critics to the reduction gearbox that Doggy has built. And that is not just because I know him and he has taken my 3D printer away from me, but the actual printed gears do work well!

At the moment I am powering Scania R620 which has been bastardised a little to have 10mm more ground clearance and a plastic tub that acts like a halfpipe tipper (lol, my lil guy loves it!).

Having original tamiya axles I have to say that the only big disadvantage of the rig is that it can't climb over difficult terrain uphill as both axles are having opened differentials. I'll post some videos later.

The positive ones are already mentioned, but I'll repeat my favourite ones:
- running stock motor (saves you few bucks doesn't it)
- running stock motor on MFC, without fearing of burning the MFC
- all sounds match the motion of the rig. Previously I've been running Hobbywing 21.5T & Justock ESC but that had problems with sound sync.
- the reduction being installed after the gearbox unloads the gearbox off the drive torque, where the motor mounted reductions load the gearbox much more than the proposed solution. That said, you still shouldn't shift gears under load.
- the rig has lots of power now
- the rig can brake well when loaded heavy

I've also tried a 80T motor from RC4WD, but that was a huge disappointment as this motor has literally no power!

So, with this post, I'm going back to the shop.

Cheers all!

Last edited by trewq; 06-12-2016 at 12:21 PM.
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