Hi everyone, just wanted to start a thread to document the building process of my crazy 8 wheel design! You may or may not have heard of me toying with this idea on this forum before, but you can see that here.
I have been riding around on my previous eSk8 build (which had an SK3 motor that blew apart after a year of use) which is now an unpowered 8 wheel setup using some mounts I found on eBay. I must say, it helps going over large bumps a ton, even on tiny 70mm wheels!
I plan on using 83mm wheels, and only 2wd, as opposed to 4wd as seen in my other post, since 4wd would be quite expensive, and complex, because it requires 4 wheel pulleys, and a tensioner.
If there is enough interest, I could start selling these mounts for 50mm motors. The beauty is that you can use it on any truck! I have a preliminary design, but am not ready to release it yet, as it will need to go through some stress testing.
Here’s a parts list for what I intend to use:
10S4P Samsung 25r from my previous build
2x Ollin OM5065 200kv
2x VESC 4.12
Custom Enclosures for both the battery & VESCs
36" kicktail deck from skateshred
2x 15/40 15mm pulleys
I just received the motors, and they are beauties!
I’ve been wanting to see one of these for a while!
Haha that’s the best gif I’ve seen all week
Some progress as the parts start rolling in. I finally got around to designing the motor mount in CAD, and fitting the OM5065 into such a small package was no mean feat! It’s such a tough balance between leaving enough room between the motor and the truck shaft, as well as having enough clearance under the deck. I did it though! Here’s a render of the preliminary design.
The mount itself is 4 pieces. The main block, and two press fit inserts for each wheel (using shoulder screws as shafts for the wheels), and a bushing for the mount to pivot on the truck. I would have made the whole thing out of one solid block, but it would use up way too much material, and be costly. This way should be just as strong, and cheaper to make!
I managed to find some free time in the shop and machine the first operation of both motor mounts. This is what it looks like!
First operation was a piece of cake. Very little setup, just stick a block in the vice and go… hardest part was dialing in the center hole diameter for the press fit bushings. You can actually see a little ledge inside the hole, which is the transition where the hole goes from being slip fit to press fit. This helps the process of press fitting parts immensely, because the part is already aligned when you force it in!
Second operation on the flipside of the part is next, and will be more time consuming. I will need to cut some soft jaws to hold the part. Thankfully, the design of the motor mounts and un-powered mounts is similar enough that only one set of jaws needs to be made for all the parts!
Got one of the motor mounts mostly done today! I also got a good start on the un-powered wheel mounts.
Here are some pictures of the motor mount with an OM5065!
The truck bushing is now pressed in, but unfortunately, when I got home, it did not slip onto the truck axle, so it will need to be drilled or reamed. Now all that needs to be done is machine the axle spacers (press fit into the large holes seen in the first photo) and this mount will be complete!
I’m very happy with how this part turned out. Nothing like success on the first try!
This is great !!
My friend and I have been thinking on doing something similar but will follow your progress on this, Nice work
This is how I first tested the concept of having more than 4 wheels. I tried it on my single SK3 with only tandems in the front, and even when going down to four 70mm wheels in the front, the board was still able to handle bumps and cracks better than the two 83mm wheels I had up front.
Yep I confirm you are right about handling, it goes very smooth and crack or bump with me no longer a problem, compensate is acceleration a bit slower due to higher friction
Finally finished the tandem mounts! Here’s a photo.
It was only after I pressed in the inserts that I realized the front mounts didn’t need to be nearly as offset as the rears, but we’ll see how it looks once I get some wheels on it.
I also finished another piece, the VESC enclosure. I based the design off of the other one I made. Still need to make the bridge for the top MOSFETs, but it is mostly ready to go.
This was made with a slight radius on the two shorter walls to match the radius of the deck I will be using. I did some 3D milling with a ball endmill to get the contour just right. Will post more photos soon, but all the parts are still in the shop, and I’ll be heading out for the 4th of July weekend.
More progress! Finally got the tandem trucks assembled with belts and pulleys! Here’s a quick look at them.
I also got some work done routing some channels into the board to run the wiring. The front and rear channels are for headlights & taillights, while the middle one will run power from the battery enclosure to the VESC enclosure.
Here’s a quick picture of the battery enclosure I made out of some sheet metal and some CNC aluminum end caps. I secured the end caps to the sheet metal with some JB weld on the inside to keep things strong and sealed. The holes in the end will house some plastic aviation plugs that I will use for charging (middle for main power, and two sides for balance charge. The 10S4P battery is actually two 5S4P batteries that my loop key connects in series. When the loop key is disengaged, I will balance charge as two 5S packs. I ran this setup on my last board with zero issues).
Very cool. Nice looking mounts. For some reason I thought you were going to power each pair of wheels with one motor, but I guess it’s not really necessary. I keep looking at this setup and thinking the next variation would involve 4wd with some custom tank wheels and tank treads.
Can’t wait to see this thing in action!
The design I have should be modifiable for a 4wd setup. It would require a tensioner pulley to keep the motor pulley having enough teeth of engagement. I’ll consider upgrading to 4wd if I have traction issues.
Love the design so far! Are you concerned about any wheel slip when accelerating or braking? Only asking because you’re limited to 1/4th of your weight on each of the powered wheels at best. I’m also loving the enclosure you’ve come up with. Guessing the battery enclosure is 5052? How thick?
I’ll actually be attending WPI next year, and am also working on a diy board. We’ll have to meet up sometime, I’d love to see this monstrosity in person.
We shall see how well the wheels grip the road. I’m planning on keeping the VESC settings pretty gentle. If I run into issues, I can modify the motor mounts for 4wd.
The enclosure for the VESCs is billet 6061 Al, and the battery enclosure is made of some sheet metal I found at home depot and some 6061 end caps I made and JB welded on.
Unfortunately, as I finished building the board, I ran into issues with my VESCs just that I am now resolving. One VESC was from my old build that I just had repaired by someone at Enertion. It blew its DRV upon motor detection (checked for shorts, none), and the other VESC I bought off of a friend doesn’t seem to want to send any current through the motor despite showing me no faults with the DRV. Might be a little while before it gets up and running due to the fact that I don’t have the money to shell out for 2 new VESCs while I figure out what is wrong with these.
Congratulations on your decision on attending WPI! What’s your major?
Wow, quite unfortunate that both VESC’s died on you. Good luck on getting that resolved. Did you even have the opportunity to see how it spins? Also, I think we’d all love to see some more pictures of the full setup if you had the chance to assemble or have any on hand.
I’ll be studying RBE. What about you?
Just resolved the issue. New FOCBOXs on the way to replace the broken 4.12 boards! Really excited to see how well the newer design works on my eSk8!
Never got to see the wheels spin, but during the motor detection of one of the VESCs, got to see the motor spin! It was very quiet, and seemed very well balanced. Looking forward to seeing it with the new FOCBOXs!
Not much else to see for now, but here’s a picture of the new deck with the trucks on it. I routed out some channels for some through-deck wire routing. Should be so much cleaner than my older builds with external battery to ESC wires!
Edit: I’m going into my senior year as an ME student!
Well, I guess this is a little past due since I have been riding this around for a few days. I finally got too impatient to finish everything before assembling and testing the board. So, here is the board assembled!
I will admit that the Tupperware ESC enclosure is pretty hack, but it has actually been working really well as a substitute for the 4.12 enclosure I made (that doesn’t fit the FOCBOXs). I’ll be making a new one that has the features of the FOCBOX aluminum heatsink so I don’t have to use the one included with the ESC, which will allow me to make a lower profile enclosure.
I didn’t end up covering the entire deck with grip tape because I realized quickly after my first test run that I want to move to a different style deck, since I hadn’t expected the motors to run into the deck while turning. I’ll be moving to this style deck for more clearance. Any suggestions for brand? I’ve never spent more than $40 on a deck, and am ready for something a bit higher quality, in the $50-$100 range. I might make a new thread for this topic, who knows.
You may also notice the cans of the Ollinmotors have turned silver. I removed the black finish using scotchbrite. I did this because I let someone ride my board, and he accidentally messed up the finish on one of the motors. When he turned the board around by hand, one of the motor mounts flipped upside down. He foolishly rode the board 100ft down the road as I chased him yelling at him to stop! Amazingly, the only damage to the motor seems to be to the surface finish of the can.
Also, please excuse the hack tail light, was put on in a pinch to do some night riding!
I’ll upload some video footage of the board working once I get around to making some. Need a pole mount for my GoPro…