Aluminum pinion time

[Saito2]

Ok, so, there seems to be some differences in the experiences we've all had with Tamiya's delightful aluminum pinion gears. Perhaps we can share our experiences and possible variables like power levels and greases used that may affect their lifespan.

My personal experience is that aluminum pinions are a wear item unlike their steel counterparts. Tamiya guidebooks from BITD even show a drawing of worn gears with their teeth looking quite thin as if on the latest fad diet. Tamiya basically recommends keeping an eye on them (like they did with any wear item) and replace as necessary to "keep your Tamiya vehicle running in top condition" IIRC.

Since I don't like aluminum stains on my gears I run steel pinions. Admittedly, I am fussy and a bit of a worry-wart about anything that can fail (gradually or suddenly) and damage other components on their way out. Some of my heavier vehicles, like my Bullhead, in my youth (before I knew any better) did show wear on their aluminum pinions when I rebuilt them as an adult. These old kits all ran stock silvercan 540s and used non-ceramic standard Tamiya Grease that looks like petroleum jelly. BTW, the grease seemed ok but had yellowed over time.

Currently, I run Tamiya Ceramic Grease that comes in kits. I throw out the aluminum pinions (or rather hoard them, unused in a drawer, because maybe I'll do something steampunk with them). With ceramic grease and steel pinions, my gears don't get stained as the steel doesn't tend to shed like the softer aluminum. Power-wise, I'm on Nimh batteries and Sport Tuned or Torque Tuned motors at best. These are my experiences.

 

 Others have had issues with aluminum gears elsewhere in the powertrain. This is why it is suggested to use the all-plastic gear set in DF01 buggies to eliminate the one aluminum gear found there. The DF03's mainshaft gear is aluminum and I've seen these shredded to nothing but I've also read some folks have had no issues with them.

As suggested by others, could the microscopic particles in Tamiya Ceramic grease be part of the problem, attacking the aluminum pinions? Its this kit supplied ceramic grease the same as the separate tube available from Tamiya labeled Cera-Grease HG? This HG grease states in its description that it includes particles of boron nitride for lubrication. Or is the aluminum simply softer than the fiber reinforced plastic gears Tamiya typically uses and gets gradually "sanded" away, only causing damage to those gears once the pinions wear to the point of sharpness? 

So what is you aluminum pinion experience and hopefully includes a many applicable variables as possible so we can examine this mystery further. 

[Kol__]

My only experience to date with the aluminium pinions was a horrible noise my Mad Bull started making one day not that long after I'd bought and built it from new, probably only after less that say 8 battery packs through it, so around 4hrs use with the kit silver can. Upon inspection the ally pinion gear was badly worn. Swapped it out for a stock size steel pinion and haven't looked back. Will never run an aluminium pinion again and have bought steel for all my other cars.

I recently built a DF01 and had heard/read something about ally gears in the drive train. Upon disassembly I've got to say they do look pretty crap and weak. Do you know the part number for the plastic gears to use as a replacement?

Also in my experience so far the kits I have do not come with the ceramic grease, but rather the standard silicone grease. Maybe it's kit specific? 

[alvinlwh]

It had also been suggested by some not to use any grease at all, so you may want to add that in as a point of interest for your research. 

For me, I tend to grease up my Tamiya gearboxes with sealed gears but I do use steel pinions so will not be point of interest to your question. For exposed gears like 3R or MST, I run them dry (maybe with just spray of WD40). Most are fine except one. However it had been suggested that there are issues with my motor mount so further investigation is needed on that. 

[MadInventor]

The aluminium pinions are just cheese. The 380 in my original sand rover even managed to wear them down using a 6V NiCad and the standard tamiya grease. The only aluminium gears I've not seen excessive wear on are the TXT-1 diff casing gear and the intermediate gear it interfaces with. (This may be because they of equal hardness). I run them with the tamiya ceramic grease.

 

[Willy iine]

Aluminum pinions were the go-to for brushed motors for me back in my racing days, but these days with brushless (super torque) I don't think the lightness outweighs the benefits of durability of steel.

If given an option, I would just use steel.. or something stronger than the soft aluminum pinions Tamiya makes.  It's funny because there were aluminum pinions I used on my 48 and 64 pitch touring cars (non Tamiya) that lasted a very long time.  It seems Tamiya makes soft pinions..  Not sure why that is because it does make a mess inside the gearbox and replacing pinions is not fun.

[Honza]

7 hours ago, Willy iine said:

It's funny because there were aluminum pinions I used on my 48 and 64 pitch touring cars (non Tamiya) that lasted a very long time.  It seems Tamiya makes soft pinions..  Not sure why that is because it does make a mess inside the gearbox and replacing pinions is not fun.

I think it's caused by lack of anodising on Tamiya pinions. Anodised aluminium pinion I had in one Chinese kit didn't wear as fast as Tamiya...

[Nikko85]

All aluminium is not the same, there are lots of different grades and tempering. Some will be much harder and resistant, so it seems Tamiya use a lower quality Aluminium, I'm sure there are other aluminium gears that would not degrade against a plastic.

 

[alvinlwh]

2 hours ago, Honza said:

I think it's caused by lack of anodising on Tamiya pinions. Anodised aluminium pinion I had in one Chinese kit didn't wear as fast as Tamiya...

 

23 minutes ago, Nikko85 said:

All aluminium is not the same, there are lots of different grades and tempering. Some will be much harder and resistant, so it seems Tamiya use a lower quality Aluminium, I'm sure there are other aluminium gears that would not degrade against a plastic.

 

Tamiya using lower quality parts requiring the user to buy hopup parts is not new. That is why there is a "big 3" essential upgrade for most kits, steel pinions, bearings and oil shocks. Things that are standard OOB in most of my non Tamiya kits. Even a £60 toy grade kit I recently got comes with bearings and steel pinion OOB. 

[No Slack]

In the past I worked in aircraft industry and learned that there are many sorts of aluminium. Aluminium 6061-T6 is a heat treated aluminium and has a good strenght to weight ratio. It is used in the bicycle industry. Another common aluminium is 7075, also heat treated and 7075 is considered stronger than 6061 in certain applications. Could it be that Tamiya buys in aluminium pinions that are not heat treated? Maybe a cost saving? And do we know the specifications of the pinion aluminium? I think not so it will be a very low quality aluminium.

It can be an interesting project to heat treat some Tamiya pinions and see if there is less wear. This requires special equipment but maybe one of the TC members has access to this and give it a try.  

[Willy iine]

3 hours ago, Honza said:

I think it's caused by lack of anodising on Tamiya pinions. Anodised aluminium pinion I had in one Chinese kit didn't wear as fast as Tamiya...

I was referring to why Tamiya does not sell aluminum pinions that are stronger, not why some aluminum are softer than others.  They can sell TRF versions with their odd pitches that are hard to find at premium prices.  I’d buy them if available.. given it was pre-2000 and brushless motors weren’t available as they are today..  but again this is just me.  

[Honza]

@Willy iine ah, sorry about that. In that case, it's just another Tamiya thing... Apparently, they have capacity for surface treatment of aluminium parts, so they could do better pinions, if they wanted. 😀

@No Slack I think that heat treatment is not needed, we use soft plastic gears and they work well. Problem is with surface treatment, or lack of thereof in case of Tamiya. Anodising drastically improves surface hardness of aluminium. It can be even done at home.

[Pablo68]

I have had pinions wear out, but not too many. More of a thing from back in the day when I would run my Hornet mercilessly, over and over and over.
These days I have a few different Tamiya buggies, so they don't all get run that regularly.

Now that I think about it, it's luck that the pinion in my Monster Beetle is brass. That one got run a fair bit and has a brushless system installed.

[Saito2]

7 hours ago, Honza said:

Anodising drastically improves surface hardness of aluminium. It can be even done at home.

Almost curious to try this along with a different grease @Juggular recommended.

[AJB123]

My Fox back in the day wore out its original aluminium 15 and 18T pinons running on non-Tamiya molybdenum grease that my Dad had once I'd used up the tiny Tamiya tube of moly grease. We bought replacement pinions from the local model shop. (We as in I needed, and I expect my Dad bought!)

It was only when I dug it out of the loft a few years ago and replaced the worn out driveshafts etc., once this here internet thing had been invented, that I read about ali vs steel pinons, and that Tamiya ali ones were hopeless, etc. I figured I'd only totally worn out two in all the time I ran that car, so they couldn't really be that bad... But then held a magnet to the pinion that's been in it all those years, and it was steel! So we must have accidentally bought steel replacements back in the day!!

So yeah - my experience is that the kit aluminium ones wore out (to the point of no teeth left and a horrible noise), but the plastic spur survived and an aftermarket steel replacement lasted way better.

[Juggular]

How long can we drive our cars after replacing the engine oil with WD40?  Probably not very long.  Proper lubrication is important, even if you have all-steel parts.  

1) Tamiya would use cheap aluminum.  They'll go cheap for grease too.  So, I use Teflon grease instead of Tamiya grease. Tamiya ceramic grease isn't bad.  It's better than sticky automotive grease that could damage plastic gears. 

But if ceramic grease was totally effective, Tamiya would not sell even finely powdered ceramic HG grease --Boron Nitride is a good lubricant for steel. It sticks to it. Born Nitride decreases wear on steel-to-steel application. It's less effective in steel-to-iron application. That's why I'm not sure it would be any better on aluminum pinions. But finer powder would be better.  (Tamiya seems to be conscientious about the material they use. They don't sell LiPo because of the fire risk. Teflon factories have had health problems before. So they might have chosen not to sell plastic beads and gone with sand beads. Even if it wouldn't be great on aluminum gears. I prefer to use Teflon grease, though. Unlike Teflon coated pans, I don't plan on cooking with Teflon grease.)    

(I can't remember where I took this photo. I think I have about 20 models that are second-handed. The pinions come in a various state of wear.) 

1000 grade aluminum is used on easily bendable stuff like aluminum rivets for small craft projects. Aluminum cans are often made with 3000 aluminum.  My guess is that either 1000 or 3000 grade aluminum is used for Tamiya pinions.  Their machine tools would last long if it carves soft aluminum.  They are certainly not 6000 or 7000 level aluminum used on aircrafts and iPhones. Those are more expensive than steel.  

The teeth developed ledges where the gears didn't mesh. This was replaced. Otherwise, it would turn into something like below. 

These aluminum pinions are not much different than brass pinions of olden days in terms of strength... just cheaper.   

Pot metal gears are not stronger either.  

\

But if you use ultra-sticky grease, the wear could be almost gone. The thickness of the grease prevents teeth to actually meet.  Something this thick should NOT be used on normal gears, though.  It would slow things down and overheat the motor.  (I do this only for diff gears, to turn them into Limited Slip Differentials.)  Never on pinion gears.  

Below is from my 20 year old Wild Willy 2. 

I think I used Tamiya grease for a while and then switched to Teflon grease.  At any rate, I must have gone through 2 dozen packs at least.  It's a silver can, but it's also twice as heavy as the Grasshopper.  But the pinion isn't in a horrible shape.  It developed weird steps on several teeth, I have no idea why.  But I have a feeling that it would have been worse if I didn't use Teflon grease.  

It would take a lot more to make steel pinions wear this much. Even soft steel is about 4 times stronger than buttery aluminum.  

2) Hardened aluminum is a cheaper alternative. (They look powder coated, rather than anodized.)  Some sellers would advertise that their gears are anodized/coated with titanium. I don't know if that's true.  

I'm always curious about these things, so I tried to peel the coating on the neck. It has a thin but glassy and hard coating.  About 20 seconds of hard scratching with stainless steel made it a bit shinier (I didn't use the cutting edge, because plastic teeth aren't that sharp). I could see how it could last a long while even with a 13t, especially with good grease like Teflon. 

I guess having a powder coating is like wearing a leather armor.  It's not as good as wearing a steel armor. But you'd live longer wearing leather than a onesie pajama. So, my preference is 1) to use good grease. If I use just a silver can, Teflon grease could increase the longevity. 2) Using good grease and hardened aluminum pinion could go a long way.  3) For a brushless motor, I'd use steel and good grease.