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.

https://lh3.googleusercontent.com/-G...CCo/s800/1.jpg

https://lh3.googleusercontent.com/-m...CCo/s800/2.png

https://lh3.googleusercontent.com/-N...CCo/s800/3.png

https://lh3.googleusercontent.com/-C...CCo/s800/4.png

https://lh3.googleusercontent.com/-k...CCo/s800/5.png



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.

https://lh3.googleusercontent.com/-U...4181d761-V.jpg

https://lh3.googleusercontent.com/-Y...3e077b44-V.jpg


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.

https://lh3.googleusercontent.com/-W...73079364-V.jpg

https://lh3.googleusercontent.com/-m...73091604-V.jpg

https://lh3.googleusercontent.com/-j...73104901-V.jpg

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.

https://lh3.googleusercontent.com/-M...27475085-V.jpg

https://lh3.googleusercontent.com/-O...28802477-V.jpg
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.

Re: Tamiya bolt on reduction gear
 

I like it! How much $$$?

Reg

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.

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.

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.

Ken

Re: Tamiya bolt on reduction gear
 

Thnx, no I didnt find any other similar products. Please post links if there are alternatives.

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.

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

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.
http://i1116.photobucket.com/albums/...7/IMG_0061.jpg

Re: Tamiya bolt on reduction gear
 

PMD 4:1

http://www.gardentrucking.com/pix/Originals/t1225.jpg
http://www.gardentrucking.com/pix/Originals/T1204z.JPG

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.

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?

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

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.

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.

http://i.ebayimg.com/images/g/jy0AAO...AxW/s-l500.jpg

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.

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!

Re: Tamiya bolt on reduction gear
 

Hmm, printing gears :confused: 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 .

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.

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!

Re: Tamiya bolt on reduction gear
 

I just got a couple of these in the mail! I have to say that I am not that experienced with 3d printing but this is by far a much better print quality than stuff I have worked with in the past. My logo on the back of the cases was also a cool thing to see as it wasn't expected.:cool: I am excited to be a test dummy for these!:bounce::bounce:

http://i1293.photobucket.com/albums/...ps9yapiri1.jpg

Re: Tamiya bolt on reduction gear
 

I am happy you received them and cant wait for you to fit them on. I wanted the logo to stay as surprise :D

If anyone else wants one, feel free to contact me. I dont think I will work on it anymore unless someone manages to brake it. I will continue development of driven front axle, and update the GRU with output shaft for front drive.

Re: Tamiya bolt on reduction gear
 

"and update the GRU with output shaft for front drive"

Now ther is a great idea we have been asking for for a long time. A gear reduction and dual out put that still alows you to use the three speed.

Re: Tamiya bolt on reduction gear
 

Would love that, and what if it was possible to change gear ratio also 4-3 4-2 etc.

I'm in desperate need of five units, for the BeamHaulerMaffia.

Re: Tamiya bolt on reduction gear
 

Well the GRU with dual outputs is out there for years, you can find it on tamiya high lift models. In combo with high lift 3speed its not bad. But the main problem is it sits to low under the gearbox. I would hate to modify my truck to fit it, as I already had to modify my high lift to be able to use it offroad, and its still in the way. Thats why I want to move the front output to the side of the gearbox, but then you will have to use my front axle.


@ Bo Wallen: I can change the gear ratio. Right now the gear ratio si 13-44 20-38. I would say thats a max for plastic gears with 5mm shafts. I will try swap 13T to metal 10T to test the speed on that. But if you want to change it to go faster, there is no problem to make few other gears.

Re: Tamiya bolt on reduction gear
 

I'm jealous now. I haven't got my own logo on the reduction unit... :cop:

Just a tip for the prop shafts, make a beefy one as your torque will be more than 6 times greater now. Here is what has happened to my mid drive shaft after ~15 battery packs, most of the time full loaded truck;
http://i1122.photobucket.com/albums/...pseklqkxgh.jpg

I think that the pin has pulled out of the one ear slowly and I never bothered to check the drive train for this kind of issues.
Once you install your reduction gear you should be very careful if you are shifting gears on the move and with load. I have stripped the third gear cause I was full speed in second and then I decided to shift higher (off throttle, but with lots of speed). The third gear is broken now :D
After that incident I started to shift gears only when stopped and the gearbox unloaded, like if you are on a steep climb and loaded - not the best idea to shift gears then.

The cool thing is that in first gear, you can crawl everywhere with a loaded truck. Like a trailer crawler ha ha ha
There is no problem climbing uphill very steep roads. The only problem is if you wanna go down hill the same way, as the original Tamiya axles are running opened diffs, as soon as you loose traction on one wheel the other one lets go and I ended up having my ~30kg loaded rig going down like crazy. I broke few things too. I reckon I'll wait for Doggy to design and build the remote locker for Tamiya axles and that should solve the problem going downhill. :p

Enjoy your mods and let us know how you like the truck equipped with these.

Re: Tamiya bolt on reduction gear
 

Trewq is testing the the unit to its limits. :D A true test pilot:jump:



And today I worked on AWD GRU unit. This version has front output on the bottom, and I also will try to make other version with the output a bit higher on the side. With this design I can also change front/rear gear ratio independently, as my new front axle will be 38-14, and rear tamiya axle is 40-15.

https://lh3.googleusercontent.com/-N...00/AWD%2B1.png

https://lh3.googleusercontent.com/-H...00/AWD%2B2.png

https://lh3.googleusercontent.com/-L...00/AWD%2B3.png

Re: Tamiya bolt on reduction gear
 

Looks almost like a Tamiya F350 3 speed tranny except that the motor is reversed.

Re: Tamiya bolt on reduction gear
 

Your new design for awd looks promising Doggy, but will the bottom front output be a through shaft for a rear output too?

Re: Tamiya bolt on reduction gear
 

Well it can be if I want it. Right now I did few variants like this, as I want to be able to put it on stock tamiya euro trucks, and driveshaft goes over battery box, so if I put rear output on the bottom, I will have to remove the battery from stock position. But yeah, its easy to make the output front/rear one the same lower shaft if someone needs it like that. But this design will be easier to put clutch on it, to disconnect front drive when wanted, or when in 2. and 3. gear. I will try to work out a way to use stock gearbox gear selector, to engage front drive only in 1. gear. But first I need to test the design in reality. US style trucks have enough space so it will fit on them without problems.

The above design is not really what I wanted for my build, today I did a new version that sits more on the side, so I have a straight driveshaft for my front axle.

https://lh3.googleusercontent.com/-Y...D%2BV2%2B1.png

https://lh3.googleusercontent.com/-D...D%2BV2%2B2.png

https://lh3.googleusercontent.com/-4...D%2BV2%2B3.png

First prototype, this is harder to install. First GRU was 2min job, but for this, few truck parts will have to be removed to be able to install it. And I think I will have to modify battery tray as there is not enough space.

https://lh3.googleusercontent.com/-T...CCo/s800/1.jpg

https://lh3.googleusercontent.com/-1...CCo/s800/2.jpg

Re: Tamiya bolt on reduction gear
 

Is the reduction with the transfer case ready for sale? What is the price?

Re: Tamiya bolt on reduction gear
 

No, its still in the testing right now. Will know the price when its finished.

Standard GRU is $50US.

Re: Tamiya bolt on reduction gear
 

just let me know when a standard gru is ready

Re: Tamiya bolt on reduction gear
 

I want one of each to begin testing In the BeamHaulFleet. So put me i Q. Please

Re: Tamiya bolt on reduction gear
 

No problem. I hope to have standard units ready for shipping next week.

Re: Tamiya bolt on reduction gear
 

I upgraded the 3D printer this weekend so I can print at temperatures above 300C, to be able to print exotic and stronger materials. I had to recalibrate to thing to get the best results. I still need to machine shafts for GRU's an then they will be ready.

I fitted AWD reduction on my truck today, I still have to machine few shafts for my new front axle, so hope to have AWD truck running soon.
Here are few shots of the new setup.

https://lh3.googleusercontent.com/--...03_1538234.jpg

https://lh3.googleusercontent.com/-2...03_1538313.jpg

https://lh3.googleusercontent.com/-x...03_1600158.jpg

https://lh3.googleusercontent.com/-Q...03_1608450.jpg

The servo is a bit tilted, so it would be better to move it on to the next hole. But there is no harm if I leave it like this.

Here is how the new axle looks like. I really like how it turned out, cant wait to test it.

https://lh3.googleusercontent.com/-D...03_1611385.jpg

https://lh3.googleusercontent.com/-0...03_1616561.jpg

So idea is to slide this 2 parts over the cental case, and when you put the axle on the leaf springs, you push it to the end to lock the axle on the leaf springs, then secure it with bolts.

https://lh3.googleusercontent.com/-1...03_1620209.jpg

https://lh3.googleusercontent.com/-l...03_1620580.jpg

https://lh3.googleusercontent.com/-S...03_1622498.jpg

Only problem is, as I wanted more space, I had to turn diff internals other way around, so the axle rotates in the other directions now, so if using stock tamiya rear axle, I need to turn it upside down, to get it spin in the same direction as the front.

Here is a video of testing if new design works:D Cant wait to do the axle so I can test it on the ground with load.


https://youtu.be/XDZABSqhNZQ

Re: Tamiya bolt on reduction gear
 

Front axle is now compete and fitted.:D This is the first version, still need to rework some design on the inside, to have better fit, but this will work good for testing already.

Hope you like it and its more clear where I was going at with my design.:)


https://lh3.googleusercontent.com/-u...04_1814229.jpg

https://lh3.googleusercontent.com/-2...04_1814290.jpg

https://lh3.googleusercontent.com/--...04_1814409.jpg

https://lh3.googleusercontent.com/-f...04_1826004.jpg

https://lh3.googleusercontent.com/-D...04_1923559.jpg

Re: Tamiya bolt on reduction gear
 

And here is a short video of it running

https://youtu.be/o7yvGBWgt3w


And front wheels with offroad tires mounted on the axle. Next is raising rear axle 10mm, fitting and test run!

https://lh3.googleusercontent.com/-X...04_2003074.jpg

Re: Tamiya bolt on reduction gear
 

And finished!

https://youtu.be/zlmRlbCnmb4


Before

https://lh3.googleusercontent.com/-W...73079364-V.jpg

https://lh3.googleusercontent.com/-m...73091604-V.jpg


And after

https://lh3.googleusercontent.com/-t...04_2159594.jpg

https://lh3.googleusercontent.com/-S...04_2159544.jpg

https://lh3.googleusercontent.com/-7...04_2159426.jpg

Re: Tamiya bolt on reduction gear
 

great design work on the bolt-on transmissions, and front axle) The original transmission for sure take up some space in the first place...Tell me, is the advantages with 3 speeds so big, that one easily look away from the space and backlash issues? I just got compact servonaut 1 speed planetary gearmotors in my trucks, never personally missed the 3 speeds, with the large steps between them, I must admit. But sometimes I'm thinking it could be fine with a second speed to choose from with full load in the steepest hills, just like a 'kick down'. Say one speed is 1:1, and speed 2 is 1:1.25, quite close step.