how to mount a v belt pulley to a rear wheel

Toby woodman

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So, I'm wanting to attach a v belt pulley of around 6 to 8 inches in diameter to the disc brake mount on a rear wheel. I will power it using a 2.5 hp 4 stroke engine with a 5/8 shaft. I built a similar bike using a bigger engine that used chains but it was noisy and high maintenance and required a clutch. I think there is a post on here from about 14 years ago using a direct drive 49cc 4 stroke to a whizzer belt sheave, However, I've spent a long time searching, and I cannot get a whizzer belt sheave in the UK, to pay for shipping would be about 20 pounds, or dollars for you. but the ones on ebay USA, are about 100 dollars already. so I'm trying to use a jackshaft setup using belts instead, that can be tensioned to provide a 'clutch'. the other pulleys can be attached using keywayed shafts but the rear wheel is the main problem. Does anyone have an idea on how to attach a lawnmower cutting deck style v belt pulley to a rear wheel, ideally using a discbrake mount, but I'm open to other ideas. Thanks
 
okay, from what I've seen online, some of them look to either have centre splines on them that are very thick or look to be double walled. Do you have any tips for centering the holes because while its less important side to side, because I'm using a flexible belt. I would like to try and avoid any belt length changes as the wheel spins, although I will be using a strong trampoline spring tensioner.
 
okay, from what I've seen online, some of them look to either have centre splines on them that are very thick or look to be double walled. Do you have any tips for centering the holes because while its less important side to side, because I'm using a flexible belt. I would like to try and avoid any belt length changes as the wheel spins, although I will be using a strong trampoline spring tensioner.
Not sure if it would work, but I have seen a substitute for a Whizzer Sheave by using a 20 inch diameter narrow bike rim. Don't recall how they attached it but likely using screws and washers behind the spokes
 
I done some research on that, I think to handle the torque and hills, i would ned the official whizzer mounting brakets, even if I drill my own holes in a 24 inch rim. the washer and spokes method I just think would be a bit weak, considering I'm building this bike to be reliable and smooth riding
 
I just spent an hour looking for pulleys on Amazon and E-bay. I asume you have no welder or lathe but I bet you have a sabresaw, hand dril and a large rat tail file. Good, because the most economical way is to make one. Google Chicago Diecast Pulleys. They make them in one inch increments from 5 to 14 inches. You will also need to get a piece of 1/8" steel or 1/4" aluminum a little larger than the pulley you choose. After finding the center use a compass and make the circle for the hub to go through. Then make the circle representing the center of the 6 disk brake holes. If you remember from geometry the radius of this circle will transcribe 6 times around the circle. E-Z P-Z huh? Now Notice there is a small lip just inside the edge of the pulley left from the casting. Make your outer circle match this. When you cut out the plate it will lay just inside this lip and everything should be perfectly centered. Next drill a hole through the pulley spoke and onto the plate leaving a good mark. This hole should be up close to the "V" section for the belt. Do this for the remaining 5 spokes. Then drill the 6 holes through the plate. Cut the spokes off just past the hole. When you bolt the pulley to the plate you might want to make spacers to fill in the gap there. This will make it a lot stronger. Hope this helps. Here's one of their pulleys off E-bay. You might get a better price if you call them direct or you can ask them for their dealer near you.



 
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After taking a closer look at the spokes on that pulley I see it has a center reinforcement rib. You will need to grind that off first and it might also be a good idea to cut all the spokes off at their center and get rid of the original hub.
 
Here's a different style 6 inch pulley on Amazon. I calculated the collar (hub) in the center to be 1.25 inches in diameter. I do not know what your disc brake hub diameter is, but maybe cut this collar out then inlarge the hole to fit. I have a used disc rotor you can have to copy the 6 holes if you'd like. Maybe even bolt the rotor to this pulley and you're home free. Nice thing about Amazon.......free returns if it looks like it won't work.

 
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thanks, ill have a look at the aluminium pulley's, I'm in the UK, so it's hard to get some parts, however I rang a local engineering shop yesterday, and they helped me, they suggested that I weld a taper bush to a custom made 6 bolt adapter, I do actually have some basic welding experience, and then I can attach a multitude of different large v belt and even chain sprokets to the rear wheel using the taper bush mounting. As long as the taper bush Is centered on the wheel, everything that I attach to it will be centered. The taper bush is made from forged steel, which will weld nicely, unlike most cast iron or aluminium sprokets, it also allows for a lightweight aluminium pulley to be attached using welding because the centre will be a steel taper bush.
 
Here's a pic, Toby, of the center bolt pattern you're looking for that will bolt onto any disc brake hub. I do not understand what the necessity is for a tapered steel hub or how it could be used. The easiest , but a little more expensive way to go would be to buy ANY sprocket like this. They all have the same bolt pattern. Look hard and you will find them in aluminum also. Take this sprocket and have the engineering shop weld it to the pulley you find.

SPROCKET.jpg

An alternative would be to give them a disc brake rotor to use as a pattern and cut something that looks like this . It will not have any teeth. You could do something like this yourself and save some quid.
 
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