Plastic driveshafts

[Lefse]

Hi, I see that many bigger RC cars from Traxxas and Arrma come with plastic driveshafts these days. Are there any advantages to this over steel driveshafts or are they doing it purely to cut costs? I also see that many cheaper RC cars come with steel driveshafts, so the cost saving argument doesn't necessarily make sense? How durable are these plastic driveshafts? Are they made of a durable plastic like nylon or POM or is it typically ABS or something like that?

Should I be worried about durability when buying a car with palstic driveshafts? My GF and I are thinking about buying a car together and the Arrma Vorteks have caught our eye, but the plastic driveshafts have a me a bit concerned. Can they handle the torque and load from a relatively large RC car that will be driven roughly?

I'll appreciate any insight on this as my research on this haven't been very productive.

 

[D3MON]

weight savings is a factor, price, and design.
yes the cheaper ones might have metal driveshafts, but i can tell you now that doesn't mean they are better. case in point, within a few battery packs of bashing on a brushless Exceed infinitive with metal dogbones, every shaft was bent, and that was with 6 and 7 cell NiMh cells.
arrma granite BLX 3s running 3s, arrma Mega converted to BLX but running 2s, and arrma big rock 3s running 3s and at least 10 packs on each only had one driveshaft back off, just re-threaded the screw and good to go, and when they start wearing out its about 19$ for a pair.
design (reinforcement etc) is just as important as material and not all materials are equal, cheap metal is cheap metal.

 

[Lefse]

That makes sense, durable plastic can be better than weak metal. Maybe they were aluminium or zink alloy driveshafts, or just very cheap steel? The steel shafts in my Nanda buggy seem to be quite durable. Didn't even get bent in a crash that ripped the right portion of the front suspension almost completely off. That car does seem well built though, apart from the weak stock servos.

It would be very interesting to know exactly what kind of plastic they use in those plastic driveshafts.

 

[More_Power]

I got tired of twisting up my plastic driveshafts in my 3S VXL 2wd slash. So I went to some steel/aluminum ones.

now on my 4wd slash, I knew the stock shafts and center drive shaft (hollow aluminum) would not hold up to the 2.8 tires and VXL6S power system I put on it. So now I have traxxas steel splined CVDs and techno RC big bone center drive shaft.

I think carbon reinforced plastic could hold up. But it would also require more splines than the 4 lugs that come stock on the traxxas 1/10 scale trucks. It would also require some sort of lubrication to reduce friction; thus reducing heat. I personally believe the frictional heat and absorbed heat (from the diff out drives and the transmission/motor) soften the plastic and cause it to fail. Example; I got the HD axles for my 2wd. They ran good for about 10 mins. Then the yoke at the out puts popped out of the driveshaft ears. I got the steel yokes. This condition got worse. I examined the driveshaft ears and noticed they were bent out. I could not get them to bend back in to position. That is, until I applied some heat from my wife’s hair dryer. I fixed it i thought. It ran good for about 10 mins and it happened again. Low and behold, the ears bent out again. So I deduced that it just have something to do with the heat from friction and absorbed from the diff/motor/transmission

 

[Greywolf74]

Plastic driveshafts in hobby grade kits are generally ok as long as you are using the kit as the manufacturer intended. For example a 2WD Rustler runs just fine with its plastic drive shafts as long as you are running 2S and moderate gearing. You start pushing or exceeding the norm of what the kit was designed to do and then you start having issues. Also D3mon is right too about the metal shafts. not all metal is created equal. If you're gonna go with metal dog bones make sure they are hardened steel or something equally as strong.

 

[Lefse]

I got tired of twisting up my plastic driveshafts in my 3S VXL 2wd slash. So I went to some steel/aluminum ones.

now on my 4wd slash, I knew the stock shafts and center drive shaft (hollow aluminum) would not hold up to the 2.8 tires and VXL6S power system I put on it. So now I have traxxas steel splined CVDs and techno RC big bone center drive shaft.

I think carbon reinforced plastic could hold up. But it would also require more splines than the 4 lugs that come stock on the traxxas 1/10 scale trucks. It would also require some sort of lubrication to reduce friction; thus reducing heat. I personally believe the frictional heat and absorbed heat (from the diff out drives and the transmission/motor) soften the plastic and cause it to fail. Example; I got the HD axles for my 2wd. They ran good for about 10 mins. Then the yoke at the out puts popped out of the driveshaft ears. I got the steel yokes. This condition got worse. I examined the driveshaft ears and noticed they were bent out. I could not get them to bend back in to position. That is, until I applied some heat from my wife’s hair dryer. I fixed it i thought. It ran good for about 10 mins and it happened again. Low and behold, the ears bent out again. So I deduced that it just have something to do with the heat from friction and absorbed from the diff/motor/transmission

You mention carbon reinforced plastic, whats your opinion on nylon with glass additive? Its commonly used for high load parts in airsoft guns, for example pistons, and is pretty durable. Too much friction perhaps? Airsoft pistons made from this typically needs good lubrication so maybe not ideal for driveshafts?

 

[More_Power]

Plastic driveshafts in hobby grade kits are generally ok as long as you are using the kit as the manufacturer intended. For example a 2WD Rustler runs just fine with its plastic drive shafts as long as you are running 2S and moderate gearing. You start pushing or exceeding the norm of what the kit was designed to do and then you start having issues. Also D3mon is right too about the metal shafts. not all metal is created equal. If you're gonna go with metal dog bones make sure they are hardened steel or something equally as strong.

This is also a very good point. If you plan on running the highest power for the system, sending it to the moon or trying to break the posted speed limit, the plastic isn’t going to take it. And powdered metal is not the same at tool steel. Pay the money for quality parts; you get what you pay for.

You mention carbon reinforced plastic, whats your opinion on nylon with glass additive? Its commonly used for high load parts in airsoft guns, for example pistons, and is pretty durable. Too much friction perhaps? Airsoft pistons made from this typically needs good lubrication so maybe not ideal for driveshafts?

glass reinforced plastic is used quite often in cordless tools for the cases/shells. The big difference is how much glass/carbon is in the plastic it’s self. The lower the amount of glass/carbon in the plastic, the more flexible/weaker the part is. Reinforced plastic has a high impact strength and a higher stiffness than just plastic and is lighter than metals. The reason for the lubrication is the fibers have an abrasiveness to it. Glass reinforced plastic is a little more abrasive than carbon. But carbon is more expensive than glass. In RC I think carbon reinforced plastic axles/CVDs with 10 splines (anything more than 4 splines) with a Teflon lubrication coating and neoprene dust seal/boot would be ideal.

 

[olds97_lss]

Really it depends on the truck and driver. If you drive like a fool, you can break anything and anything can have a very short life.

RC companies likely use plastic if they can get away with it for typical users. They are cheaper for them and for the buyer to replace. Less rotating mass usually and typically adds a "weak" spot that helps protect the diffs.

That said, the plastic axles on my stampede 4x4 did not hold up to me with 2S in it. I'd be lucky to get through 2 packs before popping one apart. That was with high grip tires in grass. I spent $140 and got MIP X-Duty's. I now run 1/8th scale electronics on 4S with 3.8" LP tires on it and it does fine.

Plastic axles on my nitro 2.5R jato held up ok. I'd break one on occasion. When I converted it to brushless, they lasted about 2 minutes on 2S. I replaced them with traxxas steel cvd's and they hold up ok on 3S (even a short run on 4S, but I crashed and broke other stuff).

Plastic axles on my 1.0 e-revo held up fine for 4S. I'd replace them about once a year as they would wear/stretch at the yokes and to avoid having them break, I'd replace them and keep the old ones for spares/parts.

Plastic axles on my nitro revo's, small block and big block, seem to hold up fine as well. I do break one on occasion, but it's usually due to the idiot at the wheel landing hard on power.

Steel axles on my outcast hold up ok. The ears on the dog bones wear on the centers pretty quick. I think I'm on the 2nd or 3rd set since 2018, but still running the original outer bones/cvd's I believe. I ran it on 4S for the first year with trencher 3.8's, then 6S. I now run on 6S with a larger 4092/1650kv motor and max6 esc, but I'm running the stock backflips which are lighter than the trenchers (this was due to diff issues earlier).

My e-revo 2.0 came with steel cvd's and the diff output cups seem to wear pretty quick. I got the truck in 2019 and I'm on my 3rd or 4th set of cups. The cvd's seem fine though.

For now, I'm sticking with plastic axles on my maxx 4s. I'm running 4S and the yokes are similar in size to the e-revo's, so in theory, they should hold up ok. The tube part is a bit smaller OD, so will see how it does. Traxxas does make steel cvd's for it, but I want to see how well it does as is before upgrading. If the output cups are anything like my e-revo 2.0... that will be annoying anyway.

For my CVD's/bones, I use white lightning clean ride chain lube on them. Gives them a bit of lubrication without attracting dirt. I apply a few drops after every bash so it's dry the next time I take it out. Seems to help them last longer/wear less. I recently got some Super Lube 11006 to try. It's a dry lube with PTFE in it instead of wax. Will see how that does instead.

 

[D3MON]

This is also a very good point. If you plan on running the highest power for the system, sending it to the moon or trying to break the posted speed limit, the plastic isn’t going to take it. And powdered metal is not the same at tool steel. Pay the money for quality parts; you get what you pay for.




glass reinforced plastic is used quite often in cordless tools for the cases/shells. The big difference is how much glass/carbon is in the plastic it’s self. The lower the amount of glass/carbon in the plastic, the more flexible/weaker the part is. Reinforced plastic has a high impact strength and a higher stiffness than just plastic and is lighter than metals. The reason for the lubrication is the fibers have an abrasiveness to it. Glass reinforced plastic is a little more abrasive than carbon. But carbon is more expensive than glass. In RC I think carbon reinforced plastic axles/CVDs with 10 splines (anything more than 4 splines) with a Teflon lubrication coating and neoprene dust seal/boot would be ideal.

hvae to keep in mind also, harder does not mean better, as the harder they get the more brittle they become. its finding a perfect balance of hard enough, and flexible enough so they dont break easily when it comes a time they need to flex. which can be attributed to a slipper to help save them to last longer, not very often is the slipper adjusted correctly, and landing with correct throttle speed on landings to the application each time they are ran. can see this with the carbon upgrade parts you are able to get for most cars like a-arms, hub carriers, etc. they are stiffer, but have a tendency to snap when pushed near their breaking point, as opposed to having a slight bit more of flex and return back to their shape.
the little bit more flexible driveshafts allow that little bit of extra flex so they don't snap so easy. the plastic they use is a decent all around for what they are intended for, obviously more power is typically going to require more strength because the parts just weren't designed with that in mind.
overall its a balancing act.
i will say with the 3s arrmas that i have owned, have had no issues with the stock driveshafts. now if you were to start going 4s and 6s as I've seen thats when most of the issues arise, or if the slipper is set completely tight, or newer drivers landing full throttle all the time, or a combination of both. they do make steel driveshafts for the 3s series, and if i do eventually run into issues might try them out, but i like knowing the driveshaft will have the extra give to possibly save the diffs and transmission/slipper assembly. as i am most certainly not the best driver.

 

[More_Power]

Really it depends on the truck and driver. If you drive like a fool, you can break anything and anything can have a very short life.

RC companies likely use plastic if they can get away with it for typical users. They are cheaper for them and for the buyer to replace. Less rotating mass usually and typically adds a "weak" spot that helps protect the diffs.

That said, the plastic axles on my stampede 4x4 did not hold up to me with 2S in it. I'd be lucky to get through 2 packs before popping one apart. That was with high grip tires in grass. I spent $140 and got MIP X-Duty's. I now run 1/8th scale electronics on 4S with 3.8" LP tires on it and it does fine.

Plastic axles on my nitro 2.5R jato held up ok. I'd break one on occasion. When I converted it to brushless, they lasted about 2 minutes on 2S. I replaced them with traxxas steel cvd's and they hold up ok on 3S (even a short run on 4S, but I crashed and broke other stuff).

Plastic axles on my 1.0 e-revo held up fine for 4S. I'd replace them about once a year as they would wear/stretch at the yokes and to avoid having them break, I'd replace them and keep the old ones for spares/parts.

Plastic axles on my nitro revo's, small block and big block, seem to hold up fine as well. I do break one on occasion, but it's usually due to the idiot at the wheel landing hard on power.

Steel axles on my outcast hold up ok. The ears on the dog bones wear on the centers pretty quick. I think I'm on the 2nd or 3rd set since 2018, but still running the original outer bones/cvd's I believe. I ran it on 4S for the first year with trencher 3.8's, then 6S. I now run on 6S with a larger 4092/1650kv motor and max6 esc, but I'm running the stock backflips which are lighter than the trenchers (this was due to diff issues earlier).

My e-revo 2.0 came with steel cvd's and the diff output cups seem to wear pretty quick. I got the truck in 2019 and I'm on my 3rd or 4th set of cups. The cvd's seem fine though.

For now, I'm sticking with plastic axles on my maxx 4s. I'm running 4S and the yokes are similar in size to the e-revo's, so in theory, they should hold up ok. The tube part is a bit smaller OD, so will see how it does. Traxxas does make steel cvd's for it, but I want to see how well it does as is before upgrading. If the output cups are anything like my e-revo 2.0... that will be annoying anyway.

For my CVD's/bones, I use white lightning clean ride chain lube on them. Gives them a bit of lubrication without attracting dirt. I apply a few drops after every bash so it's dry the next time I take it out. Seems to help them last longer/wear less. I recently got some Super Lube 11006 to try. It's a dry lube with PTFE in it instead of wax. Will see how that does instead.

That’s also a good point; the difference in power plant. The electric systems are going to be harder on the drive line than gas or nitro. The reason for this is an electric motor can deliver 100% of its available torque at 0 rpm. Instant full shock load. Where as an internal combustion engine makes it peak torque higher in the RPm range. This makes it easier on the drive line due to the moment of inertia; trying to hold together while being forced to go from no momentum to 100% rpm in a fraction of a second (electric motor) vs torque building as rpm increases (gas/nitro motor). Then comes the factor of vibrations/harmonics. As RPM increases, so does vibration because of unbalanced components. The unbalance causes side loading due to a spot that has unequal weight being spun; centrifugal force. As rpm increases, so does the weight as centrifugal force effect increases.

 

[Rustler1978]

The main reason is the rotating mass. Rotating mass= more work on your motor, meaning more heat, which leads to other problems. Going to a metal axle I fine, if your also ready to upgrade transmission components,and cooling options for the esc, and motor. The older velineon systems didn't take metal axles well. They got hot as poop, and had to use a fan on them even on 2s and conservative gearing of 18/83.

The main reason is the rotating mass. Rotating mass= more work on your motor, meaning more heat, which leads to other problems. Going to a metal axle I fine, if your also ready to upgrade transmission components,and cooling options for the esc, and motor. The older velineon systems didn't take metal axles well. They got hot as poop, and had to use a fan on them even on 2s and conservative gearing of 18/83.

The newer systems will do 2s on conservative gearing but still get to like 150 degrees by the time you drain a battery pack. Just be ready if you add weight to the rotation to plan on upgrading esc, and cooling options as well.

You mention carbon reinforced plastic, whats your opinion on nylon with glass additive? Its commonly used for high load parts in airsoft guns, for example pistons, and is pretty durable. Too much friction perhaps? Airsoft pistons made from this typically needs good lubrication so maybe not ideal for driveshafts?

If your axles were carrying heat from the transmission something is wrong inside the transmission.

 

[Jerold]

Hi, I see that many bigger RC cars from Traxxas and Arrma come with plastic driveshafts these days. Are there any advantages to this over steel driveshafts or are they doing it purely to cut costs? I also see that many cheaper RC cars come with steel driveshafts, so the cost saving argument doesn't necessarily make sense? How durable are these plastic driveshafts? Are they made of a durable plastic like nylon or POM or is it typically ABS or something like that?

Should I be worried about durability when buying a car with palstic driveshafts? My GF and I are thinking about buying a car together and the Arrma Vorteks have caught our eye, but the plastic driveshafts have a me a bit concerned. Can they handle the torque and load from a relatively large RC car that will be driven roughly?

I'll appreciate any insight on this as my research on this haven't been very productive.

Not trying to be a jerk here but there is some parts names that need to be sorted out. Axle shafts go from the diff to the wheels and drive shafts go from the transmission/transfer case to the front/rear diff.

Assuming you are talking about the axles shafts, then yes do the upgrade. On my slash the plastic tube is plenty tough, but the yoke breaks on the plastic. Then with the steel driveshafts the spindles are still the weak point.

I bent one center drive shaft (aluminum) on the slash. Not to self don't hit a tree. Aluminum doesn't flex like plastic.

In the end spare parts are cheap, always brings spares.