Tamiya TXT axle gear help

[Saito2]

I've got a wear problem on both my TXT-1 and Agrios in the upper axle gear train. The third gear in, right after the two bevel gears, referred to as the MR16 drive gear, which meshes with the main diff gear below, is suffering from premature wear. The gear is not splined to the shaft, but features a semi circular hole that mates with the end of bevel gear shaft MR10. This semi circular hole is wearing rapidly. The gears must be diecast aluminum, as that familar "aluminum grinding paste" (like Tamiya aluminum pinions) is present. I've seen pics of the inside hole of this gear actually "exploded" outwards and stripped. I'm trying to think of any way to bond this gear to the shaft to stop the wear. My first truck ran twin 14.4v 550s, but the Agrios runs a Castle SV2 4600 motor. The punch control is turedn up to ease driveline shock and bring the truck up to speed slowly. This has saved the driveshafts, but this gear still wears. The big problem is I can only source the replacement gear by getting the whole diecast bag at $50. I know most don't mess around with these big trucks anymore, but any insight would be helpful.

[Backlash]

I wonder what pitch the MR16 gear is??

If its something common, like Mod1, then maybe you could replace the aluminium gear with an M5 Pinion gear, and lock the gear onto the shaft with a grubscrew..

Otherwise, could you replace the MR16 gear with a new one that is not worn, and lock it to the shaft with some Loctite bearing lock or similar to stop it moving on the shaft..

OR maybe you could just reinforce the old gear by gluing it to the shaft with something like JB Weld or similar..

[Robo3]

I used thin shim stock( Steele ) on the flat spot on gear and pressed the gear on the shaft

[Saito2]

Thanks for the ideas guys! I think I'll try the shim stock on the flat and then add the Loctite bearing lock for extra insurance.  

[kontemax]

The best idea is to replace the entire gears.

Mad inventor has the machinery to make the gears, probably steel gears would be helpful.

 

Max

 

[mwitkowski]

Steel gears, Like this.  This is a steel replacement for the stock drive gear.  We are in the testing them now.  If all goes as well these will be ready for sale soon.

[Saito2]

That's exactly what I need . I myself, could use 4 right off the bat for my TXT-1 and TXT-2 Agrios. Very interested! I really love these trucks and want to keep them on the road for years to come.

[kontemax]

4 hours ago, mwitkowski said:

Steel gears, Like this.  This is a steel replacement for the stock drive gear.  We are in the testing them now.  If all goes as well these will be ready for sale soon.

These are great!

You should make also the diff gear. Would be great with a ball differential inside.

 

Max

[mwitkowski]

16 hours ago, kontemax said:

These are great!

You should make also the diff gear. Would be great with a ball differential inside.

 

Max

We are working on a new diff, but not a ball diff.  We are also looking into steel replacement gears for the trans.

 

[kontemax]

I will be a buyer probably. Will you do it for the Clod also?

Do you have a website?

Don't forget to post the parts in the Design section.

 

Max

[Xeqshnr]

Thought Id chime in on the drive gears. My TXT has been the test bed for them, running a 3500kv 1/8th scale motor on 3s, and I havnt been nice to them lol. So far things are going well, I did shear off the shaft the gear rides one time at the snap ring groove. The D hole in the gear is holding up well. The ring gear on the diff is showing some wear but Im trying to determine if thats going to be a problem or if its just the 2 gears breaking in. Youre definetly not going to twist the center out of these.

[MadInventor]

On ‎01‎/‎10‎/‎2016 at 11:28 PM, Xeqshnr said:

Thought Id chime in on the drive gears. My TXT has been the test bed for them, running a 3500kv 1/8th scale motor on 3s, and I havnt been nice to them lol. So far things are going well, I did shear off the shaft the gear rides one time at the snap ring groove. The D hole in the gear is holding up well. The ring gear on the diff is showing some wear but Im trying to determine if thats going to be a problem or if its just the 2 gears breaking in. Youre definetly not going to twist the center out of these.

just found this thread and it's very interesting to see someone putting some after market development work into this trans. Interesting about the comment about the shaft shearing off. Perhaps a solution would be to manufacture a replacement shaft as well. Given the machining effort going into putting the internal flat on the gear, I would take a 6mm shaft, use  a spline for the flat gear, put an 1160 bearing in the centre of the shaft, then turn the other end of the shaft down to add the spline the for the bevel gear. If the straight cut gear is made to the right size the retaining circlip should not be required, which means no snap ring groove and a stronger shaft, a simpler manufacturing technique for the replacement straight cut gear.  I'd actually be tempted to make the straight cut gear and shaft out of 1 piece of steel (No flats or pins or glueing required then, then machine the shaft with the spline for the bevel gear, which a 1160 bearing should fit over. That should then be a massively strong solution.

I'd be interested to see what the manufacturers think of this.

Also, have you seen the mod I did to my TXT axle to fit a TT-01 one way roller unit in it ? Would be very easy for me to get an off the shelf gear to make a final drive gear for this mod, if I knew what the module / dp of the final drive gears is.

I have also designed and built an effective replacement gearbox for the TXT-1 that is designed specifically for using a single 1/8 motor, but retains the use of the standard TXT gears.

I've no intention of making any more of them, but I do think it is a good design if you want to use a single brushless motor in a TXT, so there might be a market out there for them if they can be made cheap enough.

PS, Sorry for the bit of the thread hijack, the gears you've come up with look great, I'd like to know the module of them, I do think that the steel gear is going to eat the main diff gear though, and that you will need to make that from steel as well.

[Xeqshnr]

I used an online gear calculator and it came out really odd... like MOD 1.2. Its definetly something Tamiya made just for these axles. Have you seen the Solidworks files of the TXT on Cadgrab?? Really cool stuff there and from what I have checked its accurate. My original thoughts on the drive gear was to have the shaft and gear one piece. I only sheared that shaft once and it was in the front axle... odd since the rear takes more punishment. So far the replacement shaft has held up. 

[mwitkowski]

For some reason, I was not able to use the Solidworks files of the TXT on Cadgrab. To get the correct pitch, I went old school and used an optical comparator and copied what Tamiya did.  The verson of the gear you see above, doesn't need the "c" clip to hold it in place.  We made a shoulder on each side.

MadInventor, I am impressed with the work you have done.  I love reading your threads and I am always amazed with the work you do.

[MadInventor]

4 hours ago, mwitkowski said:

For some reason, I was not able to use the Solidworks files of the TXT on Cadgrab. To get the correct pitch, I went old school and used an optical comparator and copied what Tamiya did.  The verson of the gear you see above, doesn't need the "c" clip to hold it in place.  We made a shoulder on each side.

MadInventor, I am impressed with the work you have done.  I love reading your threads and I am always amazed with the work you do.

Thanks, but I'm just a bodger with a mill really

I certainly couldn't produce the gears you've shown above. I'd be interested to know how you manufactured them , particularly the flat on the inside of the gear shaft.

 

[mwitkowski]

The gears wear drilled and milled on a CNC machine, Then the "D" hole and gear profile was cut on a wire EDM machine.

[Mr. Horsepower]

Apologies in advance to resurrect such an old thread but I have the exact same issue as Saito2. It would be very nice to have an option for steel MR16 replacements but it seems these never were made available for sale and neither @mwitkowski  or @Xeqshnr have been seen here for at least a few years now. Saito2, did you ever have any luck implementing any of the prior suggestions to help manage the problem?

It seems to me one of the biggest issues with the stock MR16, in addition to the material, is that the entire hole area is weakened by being so thin walled. Not sure if this will work but I'm going to try filling in the surrounding area with JB Weld to see if it's enough reinforcement to at least help slow the deformation of the hole and flat. Once I've run it for a while I'll post back with my findings.

 

 

Edited March 16, 2022 by Mr. Horsepower
spelling mistakes

[Rb4276]

I have 4 of Mark’s  (mwitkowski) steel gears that i may part with. They are brand new I bought from him over 2 yrs ago. I dont recall what i paid for them.

[Mr. Horsepower]

Well, if you do decide to sell them I would absolutely want two pieces. Thank you.

[Mr. Horsepower]

So I was never able to get any of Mark's steel gears. But luckily similar pieces are now being manufactured in the far east. Got four steel versions of the MR16 from RCdamper on eBay. At first glance they seem well made and match up well with the stock part. Thus far my JB Welded stock gears seem to be holding up okay but when they do fail I'll try these out. I've asked if they have any plans for a replacement star shaft. No word on that yet but hopefully they do.

 

 

[Saito2]

I fixed the potential future problem by selling the truck. Then I built a TXT-1 with Clod axles. Problem solved. Sort of...lol. Seriously though, I'm glad you got some steel gears.