I completed the other mount. Much easier than the first, my drill press issues were just a combination of small errors, issues with clamping properly, my hole punch was too sharp, and wasn’t creating big enough round enough holes, and I wasn’t taking enough time to triple check everything was lined up correctly.
I might end up replacing the drive train if these belts wear out too fast, otherwise I’m probably going to go all in and make a 4WD build next.
Either way, it’s been a blast, and I’m super happy with how this board performs as a first build. I’m calling this done for now, am working on a better ride video, learning how to ride better. Thanks everyone for your suggestions and feedback along the way.
I haven’t even built my mountainboard yet, but I can already tell how our of balance the wheels are. Could you just get some stick on weights that they use for auto wheels? That’s what I’m going to try.
Hmm, I haven’t noticed any problems with wheel wobble at those speeds, maybe I just got lucky. They’re definitely not well balanced, but it doesn’t seem to be a problem for me.
Had my first major failure with the motor mounts, both of the zinc brackets cracked and fell apart. It is still ridable, but the mounts are now jiggling all over the place, not ideal!
I also have had plenty of belt skipping while braking heavily, and have decided it’s time to go with 15mm HTD pulleys, with shorter belts and new mounts.
I ordered a set of 72t and 17t aluminium pulleys, with 84t belts from sdp-si.
Those big aluminium pulleys are beautiful. Shame I had to destroy them! Used a hole saw in the drill press to cut out the inner part. Was a bit worried, but it was OK. Just took it slow, and make sure you remove the grub screws first, they worked their way out and caused trouble.
I measured up the radius of the MBS hub screws again, and calculated where all the holes needed to be. Have learned a few things since the last try! I used this calculator to figure out the lengths between points and used digital calipers to mark them.
Just to follow up, I got the mounts done, and it’s working great. I actually did a separate thread detailing the mount design/build.
I ended up having to replace the M4 bolts I had used to fit the pulleys to the wheels with longer ones, which was kind of a nasty job, but necessary to pad the wheel pulley out further and make sure the motor pulley didn’t rub against the wheel.
It’s a lot better with the new belts. There is less flex/give in the whole drive train, so everything feels tighter, and more responsive. There is no belt skipping while braking with the belts much looser than before, so I think it actually rolls more freely now, should be more efficient.
I’ll probably round off the mounts to fit the motor profile to make them look nicer and a bit safer.
Really nice build log… with lots of photos and comments… I like that
Seems like you have gone through a lot… while making it possible
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I have not posted my build pictures yet… still quite a lot of things to improve (from visual side)… though Im already looking into building a more compact deck / board… the one I’ve got now is just a monster… it is about 42.5’’ in lenght, +/- the motor mount,
got to measure the original lenght of the board.
So - looking at your somewhat compact board was a treat to me… though… looks like I’ll have to make some sort of wedges too… if the stock ones does not fit the new deck I’'ll get.
Hi, nothing new to share really. I’ve still been enjoying riding it, and haven’t had any more technical issues. My problem right now is that it’s still currently drying out after I accidentally rode through a pretty horrific pile of cow shit, and got it splattered all over the underside! Maybe a case for the ESCs/batteries isn’t such a bad idea after all, just to make cleaning easier.
I’m finding the lack of torque with the new pulleys a little annoying too. 17:72 is really not as good a fit as 16:78. I even went up to 2x5S batteries but found it didn’t make enough difference. The top speed is mental now too, I haven’t had the guts to go full throttle on the flat yet.
I’ll probably try a new build next year with some Trampa trucks/wheels, but for now this is going great.
I am working on a mountain board too but with single drive only, The problem that I am running into is with the xl belt and pully system. XL 10mm wide is causing the gears to slip. I might Chang it to dual drive. Can you post a picture of the motor mount.
I might change the gear and belt system to htd5m with 12 to 15mm wide.
It may be your belt tension is too low. Those gears are massive and engage a whole lot of area and presumably teeth, seems odd it would slip unless it’s under a lot of load.
The tension isn’t pretty good. My problem might be I am using 10mm (037)LX belts. My motor pulley is only 12 mm wide. i am having trouble finding XL belt the fit my motor pulley. The next XL belt size is 050 (14mm?) I think.
I had belt slipping quite a bit with the XL belts quite a few times, and that was with dual motor. I said it way back in this thread somewhere, but with 16t motor pulleys I am glad I went with the super long 116t belts, it looks like yours are a lot shorter. It’s all about the area engaged on the motor pulley. More teeth, wider, longer belts, or a belt tensioner will all help.
Also your wheel pulleys look quite small, that won’t help. You want the biggest motor/wheel pulley ratio you can get (while still engaging plenty of teeth on the motor pulley) to provide as much torque as you can on these kind of builds.
Honestly though with a single motor I don’t think you have a chance of driving a mountainboard wheel with a single XL belt. You either need to go with HTD 12-15mm wide or dual motor, and I ended up with both. Good luck!
I would say you need a tensioner / idler pulley! Your wheel sprocket does look quite small… have you tried to calculate how much teeth in mesh do you have?
I think it was critical not to have less than 5 teeth for motor pulley to be in contact with the belt…
That’s the reason why I also chose quite a long belt… because the calculator said there wont be enough contact between the pulleys… My belt is a bit loose and it does skip when I try to brake hard… no problems for acceleration, though!
Ive got 95T belt for 15/65 pulley system (4.33) ratio)
85T would have been better in terms of lenght but then the idler pulley would be even more welcome probably.
Indeed it does!
@dinodave, could you please post an updated parts list for your build? Yours is very much like what I’d like to do!
Can you give a rough cost estimate?
it is about 42.5’’ in lenght, +/- the motor mount,