I suppose all these guys need to upgrade their truck axles to 10mm? … cause 8mm solid steel shafts arent strong you say???
I just wish 8mm could be left as standard that way parts are just off the shelf and fit most applications.
Looks good 
6mm motor shafts can snap. I have snapped a SK3 50mm 280KV motor shaft however this well over 1k+ miles. It also hit a pothole pretty bad which is why it snapped.
Yeah same. However the sk3 spare parts were all of about $4 and easy to replace.
WTF?.. how come everyone is talking about 6mm now? it’s confusing… stop it.
the Op said
The switch to 10mm has more to do with the amount of power transfer we are dealing with. No sense in bottlenecking all this power with an 8mm shaft.
skateboard trucks have 8mm axles! so do many brushless outrunner motors! saying that an 8mm solid steel shafts is a bottleneck in terms of torque transfer ability - because they might snap? that’s a bit far-fetched… I have never seen or heard anyone say they have snapped an 8mm shaft! Those guys in the video I posted are landing HUGE tricks and rolling away on 8mm shafts…
There are plenty more bottlenecks before we need to over-engineer the shaft…
- The belt which transfer the torque is definitely the weakest link
- The motor mount itself, some people have aluminium motor mounting plates with cross sections directly next to the motor that are under 6mm! aluminium is going to snap before an 8mm steel shaft will snap!
Spruiking the 10mm shaft as an improvement of an 8mm shaft is a long stretch of the marketers imagination!
For instance what does this mean?
“fewer cases of a pulley or motor housing stripping free”
These maytech motors are crazy. I was looking on their website and found a 6374-330kv motor that has an output of 3200 watts. This would be an awesome single drive motor. I will have to look into them.
@trbt555 Understands why 10mm shafts are used on these motors I bet the engineer who designed them also knows a thing or two about torsional stress. It is easy for most people to see that we can exert more force on a pulley or motor housing using a 10mm shaft vs 8mm or “6mm”.
8mm will work fine for the average board with a top speed around 25mph but many people have issues with the motor housing spinning free from the shaft. With a 10mm shaft this will happen less frequently or not at all, testing will tell.
Our truck axles are not under the same torsional stress that our motor shafts experience. Completely different modes of operation actually, torsional versus flexural. Even a child can see that a 10mm shaft will handle torsional loads better than an 8mm shaft. Many people have experienced torsional failures and remedied this by replacing the grub screws with oversized bolts so pretending like this is not an issue is a disservice to the sport.
To say 10mm shafts are a marketing ploy is laughable. I’ll be sure to let the engineers at Maytech hear that little gem.
So now lets put the whole bent shaft argument to bed and get on with this!
These motors will be arriving in about 2 weeks. I should be all caught up on builds by then since I have an apprentice helping me out around the shop. The plan for these motors is a 40 to 45 mph top speed. We are going to gear it for a 50 mph target speed, 17/36 tooth on 90mm wheels @12s. The pack I am designing for this build will have a max constant output near 8000 watts using 30amp high discharge 18650 cells. Expecting to use around 3000 watts max.
We have one of the larger 150kv 6374 motors coming too. It will go on a single motor build with more rational top speed. Shooting for 28-30mph with same drive as the dual motor build.
I’m curious as to how a 10mm shaft will mean that a motor is less likely to fall apart?
If you are worried about the barrel coming loose (which you won’t need to with maytech) why not modify the design, instead of a flat spot on the shaft & an M4 set screw you could consider a key/keyway at that end. Or have a through hole in the shaft and bolt straight through it. That would be a viable mechanical solution to prevent the issue you seem to be having with your motors that fall apart. I suppose to be transparent we all should know what motors you are using that are falling apart?
My point is that a 10mm shaft is not necessarily going to magically make this better… In fact increasing the diameter of the shaft is increasing the length of the lever, it increases the leverage & the load at the fixture! so the force at that point where the set screw engages with the shaft will now have a greater force being exerted onto it. It could actually make the problem worse.
Also, once at high speed the torsional load one the shaft is minimal, torsional load peaks during acceleration & braking and that load is determined by the load the belt can transfer which will max out before the breaking point of an 8mm shaft.
If you plan to use a chain maybe then a 10mm shaft is better…
Don’t get me wrong! I 100% agree that a 10mm shaft is mechanically stronger than 8mm for torsional torque loads. That’s it though! It won’t solve issues that arise from poorly assembled motors.
It’s my opinion that If you have problems with motors falling apart you just need better motors with better construction quality made with better materials… Maytech is definitely the best…
Jason I read a post of yours somewhere that 15 mm belts cause alignment issues currently.
Could a 10mm shaft remedy that and give better belt alignment?
you cant really compare truck axle to motor shaft, even if they are the same dimension, they are 2 totally different animals. you would smash a motor shaft to bits if you did that sort of thing with it.
Dude? are you serious?
Why would 8mm stainless steel shafts smash to bits?
How is it possible that all the precision downhill trucks work without smashing to bits? Because they all have 8mm diameter stainless steel axles.
the only reason 15mm wide belts can be problematic is due to the arch coming off the hanger of a caliber truck, there is a point where the nice square & flat clamping area of the hanger begins to change shape - this means it’s not good for clamping to anymore, the alignment of the motor mount when too close to the centre of the truck becomes very difficult because its not square/flat.
I have calculated that a maximum belt width of 12mm is compatible. Of course you could add extra washers onto the axle and push the wheel out further. Each speed washer is normally 0.8mm thick so you need another 4 of them to allow a 15mm wide belt. But even at this point you are clamping onto the edge of an area that is not perfectly flat & square, each truck is different also, I personally prefer to keep a few mm away from the angle change that occurs on the hanger.
I have never had an issue with 15mm belts on caliber trucks. Though I’ve always run single motor setups until this last week and I’m using a randall clone on that build.
It’s mount dependent, If your mount is very thick like the current enertion mount which is 17mm thick it’s not a good idea to use 15mm belts. With the original enertion mounts, which were just 13mm thick, it would work easily because they offer more space because they are mounted closer to the wheel pulley.
Ahhh, I didn’t realize your new mount was so thick.
yes I’m serious. there are hundreds of different grades of stainless, all with different properties. none of which are used in the gap vid you posted because street skaters don’t use long board trucks.
stop using potatoes to prove salad.
@onloop
Your statement about increasing the length of the lever and thus the force is wrong.
Actually, the inverse is true: increasing the diameter will decrease the tangential force acting on the grub screw and/or key.
Torque = Force x Lever, so for a given Torque the force will decrease with longer levers, ie thicker shafts, which could be a benefit if you need to convey more torque.
But I get what you’re saying, if an 8mm axle is already OK for a given application, then a 10mm axle will not change anything.
I also agree there may be other more important weak points before a (good quality steel) 8mm shaft becomes an issue.
Maybe if I have some time over the weekend I’ll do some stress calculations for our typical setup to see in which ballpark we’re playing.
On a side note: I wouldn’t want to drop in on those precision trucks, they don’t have an axle in one piece. Failure mode would be losing a wheel instead of bending an axle 
. Those trucks are clearly designed for precision not for vert/park.
Also bear in mind that from a structural perspective, plain carbon steel is often a better choice than a lot of the common stainless steel grades.
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since I’m getting a free physics lesson I might as well ask some more questions.
So in terms of the lever & load concept.
Does it matter where the torsional load is coming from, from outside inwards vs inside outwards… when accelerating it’s coming from the outside in, when braking it’s coming from inside out.
Does this change anything?
So now that you are starting to understand the science behind increasing shaft size you can see why 8mm shafts are inadequate for driving larger drive pulley sizes under heavy load.
Of course all of this is irrelevant if you don’t have the battery pack to drive this amount of power. You can be using the best motors in the world and it would just be window dressing without the power to drive it.
Correct! I’m not a scientist, but I do have lots of experience building eboards.
I do know that the drive train is only as strong as the weakest link, I doubt many people will argue that…
Over the last 3 years of investing hours & hours on forums & building many eboards I have never heard anyone say they have snapped an 8mm shaft…
I also sell motors, lots of them… Never had one snapped shaft! Even the cheapest motors I could find in china never had a snapped shaft. Something else always gets destroyed before the shaft - normally the belt followed generally by things melting due to heat…
I also strongly value evidence & real world test data… you don’t need to be a scientist to gather data or learn from it.
For instance when I was curious about using 3mm pitch belts, I invested in various configurations and tested them to learn the facts. I realized anything under 15mm wide won’t work. This is not just my opinion its knowledge gained from doing the tests…
There is a big difference between opinion vs facts, So let’s make it clear as day - it’s simply your opinion that 8mm shafts are not strong enough.
So until you can give us data or evidence you need to stop saying stuff like
Based on the evidence presented so far there is no reason to stop using 8mm shafts. However, I am willing to change my mind when you can provide some evidence that they fail under load.
The last thing we need is people reading this thread and starting to think that 8mm motors shaft are somehow a problem that need to be avoided… As a community, we need to promote facts and filter opinion.