Crazy 8 wheel 4WD idea

Hi guys,

I just wanted to put a little idea out there for a build I am planning on starting mid-summer. I go to school at Worcester Polytechnic Institute, and there are quite a few E-Sk8s popping up all around campus, most are DIY. I saw a video of an 8 wheel skateboard, and instantaneously knew what I wanted to make. An 8 wheel 4WD E-Sk8!

Now, I know what some of you are thinking.

“It’s not cost effective.” “It won’t be efficient.” “It’s too complicated!”

But that’s not the point. The point is to make something truly unique! I want to make a board that a bystander will do a double take and say “wait… that is an 8 wheel longboard… and he’s not even pushing!”

I have already been tossing around ideas on paper. Here is one belt layout I’ve been thinking about. It’s by no means my final design, but is merely a schematic to show what it might look like.

There may be some issues with the motor pulley skipping, I’ll look into it.

There is still so much left to do. Lots of modeling in CAD, lots of machining (my specialty at WPI :wink: ), and lots of trial and error. And most of all, I have to finish my current E-Sk8 project before I head off for a project term in Copenhagen, Denmark (Really looking forward to E-Sk8ing there! Most bike friendly city in the world!).

What do you guys think? Please give me all your thoughts!


You’ve just split the majority of your torque between two wheels on this setup with one getting more than the other wheel. I might be wrong on that thought. Would be better if each wheel was a hub motor, but I know you have budget limits…

The torque should be evenly split, not that it really matters. In fact, if one wheel loses traction, the other wheel will absorb most of the torque. I think it’s more of a situational thing.

Could you explain your uneven torque theory a bit more? I don’t quite follow.

I was assuming that thought based off driving a four wheel drive car with the transfer case because power splits between the front and rear wheels depending on road condition but what you said is correct after consulting the internet about the distribution of forces between multiple pulleys assuming each pulley as the same number of teeth.

Makes sense. At this point I still have no idea how well this thing will function. But, I’m still hoping for a unique piece of engineering!

nice to see another pic of those crazy double truck things. they’re so rare even on the internet. Have you seen or ridden them in person? I imagine they handle fine. how about just getting one 63mm motor on it, especially on that little board, or any board, unless you plan to do a lot of long sustained hills or you’re heavy the extra motors are likely overkill. And you dont care. maybe get some miniature motors. i can’t imagine any benefits of having 4 motors and pulleys vs just one motor especially with the ability to drive two wheels with the one motor using that weird double truck thing…I imagine it wouldn’t effect the turning i see you have 63mm motors already planned. 4 of those you could make four boards. at least try the one maybe before going through the time screwing them all down. there are children starving in africa and you want four motors on a penny board. yuk yuk

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Oh that is just a stock photo I used to show the general idea of an 8 wheeler. My deck will be much larger.

I have not seen or ridden any, but I think I’ll machine some tandem mounts for a push rider I have, just to test it out. It may turn out that I hate it, would be valuable to know before building a whole E-Sk8 around it!

the tandem mount could be a platform on which you could put all the electronics and even the battery, and of course the motor and drive system. all on that one screw on part. that would be some cool engineering and bet people who could only turn one screw would turn that one needed screw to be turned. not your idea but I love those crazy tandem things. never even seen them in real life

This is one reason I got so excited about making a tandem mount. It would be a universal solution that could be used on any truck! Not only that, but it also widens the wheelbase, something I understand is sought after among E-Sk8ers.

this is a cool idea. My eyes widened as soon as I saw it!

however I see a few issues. first is that one of your wheels doesn’t have more than a third of the teeth in mesh. also the RPM of the wheels are locked together and that will make turning corners difficult as there is no differential.

i think the motor with its fewer teeth is more in question and in this instance it’s good. the other pulleys look like lots of teeth and will get enough engagement.
turning, I think since both wheels will be traveling on the same path they will turn the same speed.

no they wont. every wheel will have its own axis and turn at different speeds.

think so. given that these two powered wheels would travel the same path they will be traveling the same distance when turning unlike a single axle where the inner wheel has a shorter distance to travel while turning.

I have to say that I agree with @Hummie. For a 4wd car, with ackermann steering, this is probably true. However, these wheels are always aligned. Any difference in speed should be negligible.

maybe even a 2ah 6s battery or something small mounted with the vesc on top of that tandem thing. or on the outside. really like the idea of a single bolt electric drive system.

I’m probably not going to mount anything but the motor to the tandem truck, in the interest of keeping it light and responsive to the road (needs to pivot). Also, I would be afraid of the vibrations transmitted to the battery and VESC if they were directly mounted to the tandem mount.

there was a time jacob, of jacob’s hub motors, or emf, was trying to make a vesc that went in the hub motor or at least right beside it. a lot of vibrations. I’m still obsessed with potting one or at least doing a large conformial coating. I think the vibrations could be made not a problem. the battery and vibrations shouldnt be a problem I wouldnt think. not your plan though. maybe the extra weight on the truck would help keep it stable or at least the weight would resist speed wobbles

Would definitely be a great way to save space! I think you should go for it.

@hummie @Alanhunt123 yeah, you’re both wrong. but I’m not going to argue.

go ahead and do it, and then report back your findings. that’s how I have done everything. its probably negligible. I do all the things people have told me not to do. and look at me now!

it’s not arguing just talking about how it would work. look at you now?

in my mind since the two powered wheels are both the same distance and angle from the center of the truck they will have very similar revolutions from a turn. I’m still voting it’ll work without any downsides in handling until someone gives a good reason it wont work well.