Tamiya bolt on reduction gear

[RCP57]

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. I am excited to be a test dummy for these!

[Doggy]

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

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.

[fhhhstix]

Originally Posted by Doggy

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

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.

"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.

[Bo Wallen]

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.

[Doggy]

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.

[trewq]

Originally Posted by RCP57

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. I am excited to be a test dummy for these!

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

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;


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
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.

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

[Doggy]

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



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.

[tc1cat]

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

[Lil Giants]

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

[Doggy]

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.







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.

[Claus]

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

[Doggy]

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

Standard GRU is $50US.

[bigford]

just let me know when a standard gru is ready

[Bo Wallen]

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

[Doggy]

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

[Doggy]

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.









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.





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.







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 Cant wait to do the axle so I can test it on the ground with load.


https://youtu.be/XDZABSqhNZQ

[Doggy]

Front axle is now compete and fitted. 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.

[Doggy]

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!

[Doggy]

And finished!

https://youtu.be/zlmRlbCnmb4


Before






And after

[Rimrock]

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.