99cc Predator - Belt Drive - Homemade Non-Kit - My first build.

Hello all, I completed my first build about a year ago. Since then I've put over 2000 miles on it and she's running strong. I started with a kit and and that motor crapped out on me pretty soon (about 300 miles or so, maybe less). So I went to the drawing board.

I purchased a 79cc greyhound from HF and made a motor mount out of scraps. Mounted the motor and salvaged what I could from the kit (gas tank, muffler, throttle grip, etc). I made a custom battery box to hold a little 12v UPS computer battery backup battery to power lights and a horn. Put a keyswitch on that box and wired it into my battery box so with key on i get juice with key off all electrical components off as well. I also wired that switch to the kill switch on the motor so with key off it can't be cranked.

I started with a centrifugal clutch and the kit sprocket on the rear wheel. It just wasn't geared right to get going good without burning up the clutch....not to mention I had already ruined 2 wheels because the chain jumped off and got into the spokes. I just couldn't keep everything perfectly aligned on my bike. After continuing to work with the centrifugal clutch and chain i ended up ruining yet another wheel.

Back to the drawing board again. I decided to forget about the chain and go with a belt drive setup. I then came across the whizzer motorbikes that I had seen from long ago and they were belt drive (didn't remember that until I found them this time around). So I took a 20in bicycle wheel, despoked it and mounted it to the spokes on my 26in rear wheel. Put a pulley on the motor and made a foot clutch (step on the clutch to engage the belt) and away I went. Made it around 400 or so miles this time and pop went the spokes. Those 14g spokes just weren't stout enough to hold up to the torque and vibration.

Back to the board one last time. I decided there had to be a better way. I took another 26in wheel and despoked it and thought about how to attach it to my 26in rear wheel. Welding it was my first idea but my wheels were aluminum so it would take a tig welder which I don't have and aside from that, those wheels are so thin I wasn't sure I could keep from burning through them. So I lined them up as evenly as possible and clamped them down. I drilled holes in about 8 different spots around the rims and then tapped them. I used little machine screws with locktite to attach them and keep them together.

Once I got my bike all back together I took it out for a ride and I've been riding to this day. So issues with this design at all. Well I take that back, after about 1200 miles on that design I did end up breaking another wheel. Not due to design but simply that the bicycle wheels aren't much and just normal wear and tear caused it to break the spokes. It could also be to the fact that the spokes may have loosened up some over time (i didn't keep a check on it so I'm not sure if that's what happened or not). Anyway, I just swapped out the wheel and attached my pulley to the new one in the same way and I was back in business.

I've got some pictures of it that I'll be posting soon and you can check out my youtube videos here that detail it fairly well.

First Video,
https://www.youtube.com/watch?v=BJL_q_jU3Vw

Second Video (completed build),
http://www.youtube.com/watch?v=P5xs0WMpGF8

I checked that thread out...looks like that is a pretty good idea too. Probably not much harder to that than the way I ended up going. I like my way, but my way does restrict me to tire size (the width of the tire) because my pulley is right next to my wheel so a wide tire will interfere with a rub my belt causing the tire to wear on the sidewall and also causing my belt to jump off and whatnot....i solved that problem by just using a slightly narrower tire but in turn sacrificed a little on the looks (i think the beefier tires look better).

His way would allow you to have a little space between the wheel and the pulley which would solve that issue altogether. I might actually use that on my next build, which I plan to start before too long. I'm about to throw up some pictures of my build. If you haven't already, you might want to take a look at my youtube vids and get a better idea of how my pulley is attached also, like I said, not knocking harry's idea, i like it, but mine hasn't failed me in it's current design. Thanks for the response, take care.

ds

Here are some pictures of my build from beginning to end.

Next set of pics...

More pics...

Last pictures....for a good overview, check out my youtube videos I mentioned above. Here's the links to them again.

First video...
https://www.youtube.com/watch?v=BJL_q_jU3Vw

Updated video...
https://www.youtube.com/watch?v=BJL_q_jU3Vw

Thanks SB and no problem. Been aiming to post this for a long time but never got around to it. As far as performance goes, slight inclines are no problem at all, even fairly steep inclines are doable. Flat ground or downhill obviously gives you the quickest take off. On inclines you have to be prepared for a slower acceleration but like I said it's all doable. Once you're rolling it has no problem making it up hills even the steeper ones (where I live that is...in your parts with several hills it might be a big enough hit on performance to make you want to change the design). Usually around here if I have even a really big hill to climb, once I top it I either level out or drop back down and then level out and they are far and few between so even if I slow down a bit during the climb it's no big deal for me. I've taken off from a dead stop on about a 35 or so degree incline and it was a slow start, but really wasn't that bad. I had a truck behind me and they didn't seem to mind waiting for me to take off (no horns blown or anything lol) and again it wasn't "that" slow of a take off...i guess I increased 1mph per second or so. When taking off I generally give a good push with my right leg and throttle on up...slipping the clutch slightly until I'm rolling decently....slip the clutch a little more when taking off on a hill obviously.

I also considered spacers between the rims just didn't have a good option for that at the time. But it's definitely a consideration for the next build as I would really like to have bigger tires on my next one. I am curious as to why you recommend steel wheels. Would it be that they are stronger or what exactly?

Yeah in a real hilly environment a pedaling option would probably be nice to help on starts and on those big inclines but here it's not really an issue. What would be great is a 2 or 3 speed manually transmission, gear down for take offs and on the big hills then gear up when cruising. I've thought about that a lot and would like to fabricate some kind of multi pulley system that would give two different gear ratios that you could adjust by simply pushing a lever forward or pulling it back for just that but haven't gotten anything lined out yet.

I actually started with a clutch lever (old brake handle) as my engage/disengage method for the clutch but it was old and the cable ended up breaking on me. Instead of buying a new one I decided to go the route i did. Also before I got to where I am, I had it set up in reverse, it was spring loaded to keep tension on it and you pushed the pedal to release tension and stop. Then I thought about that a little more and that would mean you couldn't start the motor or get off the bike with the motor running because you'd have to have that pedal pushed down to keep it disengaged...there I swapped that around and used the spring to keep tension off the belt and you press the pedal to put the tension on the belt. That could be bypassed by some kind of locking mechanism to lock it in the disengaged spot for cranking and hopping off the bike...or use a hand lever like you mentioned with a lock on it.

You mentioned you need pedals to be legal. Technically I'm illegal here for several reasons...the motor size (99cc) in Kentucky we're only allowed 49cc max and also for speed...top speed isn't supposed to be able to exceed 25mph. I don't think it matters if you have pedals or not around here. Once your outside the motor size or speed limitations it's supposed to be registered. But this is a rural area and I haven't had any trouble as of yet from the law.

Lastly, as for the gearing...I had to do some trial and error on that. I've got the 26 inch rear pulley (which I'm not positive if that measures to exactly 26inches or not, never measured it) and then on the front I started with a 1.5in pulley which was great for take off but didn't yield the top end I wanted (I think top end speed was around 25-30mph if I remember correctly). So I went up to a 4in front pulley and that gave me plenty of top end (I was cruising at about 45-47mph) then but it was geared a little too high for good take offs, especially if on an incline. Then I dropped back to a 2.5in pulley and that was lots better on take off but still not quite the top end I desired so finally I landed with a 3in front pulley which does decent on take offs (could be a bit better) but top end is just right....max speed of 48mph downhill, but on flat top speed at 44-45mph and cruising speed between 38-40mph.

Thanks for the comments!

silverbear said:

Dusty,
Thanks for posting the video and photos. You have an interesting setup and managing to bypass a centrifugal clutch is a money saver. I'm wondering how your performance is... are you able to start up on a slight incline by belt power alone? Is it pretty much flatland travel where you are? Looks like it in the video. So how is it on hills? I didn't see the whole video as my connection crapped out on me midway.

I was thinking that the problem with not enough space between the belt sheave and the tire might be solved by putting spacers on the bolts between the two rims. I would also suggest using steel rims and with spacers then add more bolts for attachment points. Then you could have a nice wide tire and use a skinny rim for the belt.

In my area not having pedals would be an issue. I can see in my mind a spring loaded idler pulley which placed tension on the drive belt unless tension was released using a brake or clutch lever which would disengage the pulley from the sheave. Just a thought on how to accomplish what you have, but still have pedals for being legal around here.

Anyway, I find your approach interesting and inexpensive. For me the issue would be in figuring out the pulley size needed at the engine to end up with no need to pedal from a dead stop, hill climbing ability and a top speed of perhaps 30 to 35 mph. with the engine sound out a bit. So normal cruising speed in the mid twenties. If there's a way to do that with junk rims, a belt, an idler pulley and no jack shaft or automatic clutch then we're 'cooking with gas' (an old expression for when wood cook stoves went out and natural gas stoves came in a long time ago).

Anyway, nice job on your bike and I'm glad it's working out for you. It is always good to see a different way of doing things.
SB

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@CurtisFox
I also questioned SB on this but will ask you as well to see if yall have different ideas or opinions. I'm curious as to why you need steel rims? Maybe because they are stronger, easier to work with in some way or just what? I have considered steel rims before but other than it being easier to weld (which I decided not to weld them on this build) I couldn't really find a big advantage. Thanks!

Ok I see. I didn't realize they'd be that much stronger. I did figure that steel vs aluminum, obviously the steel should win the strength test but sounds like you've got experience with them and they are indeed quite a bit more stable and reliable. I myself have never touched a steel rim. My local bike shop had some in stock but I went with aluminum just because that's what I normally see on the bikes here and there around the web. Next time I'll definitely give the steel rims a go. Thanks!

MEASURE TWICE said:

I'm also doing a clutch with pulley, but am using a jackshaft and 2ea 10" pulleys. One is on the rear wheel spokes and the other on the jack shaft.

I get 20:1 or with a 2nd stacked jack shaft and some more not as large pulley 40:1 for parade speed so not to heat the clutch for 5mph stuff.

Was wondering what ratio do you get with that clutch and they great big 26"? How is the speed range with rpm at between clutch shoes fully engage to max rpm?

That idler pulley and belt arrangement you did looks neat! Is it an automatic clutch which is how mine is or did you change to a manual where you could let the bike go with engine at idle rpm by throwing a tensioner lever?

I have to see if my theoretical speed is around 7 to 20 and also 4 to 6 or there abouts?

MT

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I'm not sure of my exact gear ratio because I never calculated it. I just went with pulley's I had on hand and then picked up a couple new pulleys and did trial and error to achieve low end and top end performance I desired. I went to a site just now that has a calculator on it and it says 8.67:1 is my ratio. I inputted my driver pulley (3in) and my driven pulley (26in) and it gave me that. Here's the site... http://www.calcunation.com/calculators/machinery/mechanical%20power/belt-pulley-ratio.php?drv=3&drvn=26&calc=yes&Calculate=Calculate+Ratio

I'm not sure I totally understand your next question. "How is the speed range with rpm at between clutch shoes fully engage to max rpm?" --- My clutch isn't the type of clutch you're thinking of (I think) as mine doesn't have shoes or anything like that. I've already mentioned here and in my videos (if you haven't watched the videos, check them out, especially the update video) that my top speed with the current setup is 48mph (downhill) 44-45 mph on flat and I cruise easily between 38-40mph. I don't have a tach on my engine so I can't be sure of the exact RMPs I'm turning at those speeds but when I top out I'd say I'm turning around 4000-4500 RPM or so, just guessing. Cruising speed I'd say I'm in the range of 3300-3800 RPM.

Thanks for the compliment on my design. It's not an automatic clutch, it's manual and to engage it (put tension on the belt) you press down on the pedal with your foot and to disengage it (take tension off the belt) you release pressure from the pedal (it's got a spring that pulls the tensioner pulley back off the build).

Here's the links to my videos again.

First video...
https://www.youtube.com/watch?v=BJL_q_jU3Vw

Update video...
https://www.youtube.com/watch?v=P5xs0WMpGF8

Hope that helps answer some of your questions, Thanks for the comment.

Curt you are right. I measured it today and it measures 22" and that would make my current gear ratio 7.33:1 I came to post this and noticed you had already noted the actual rim measurement...so oh well :/ Anyway, you are correct on that.

curtisfox said:

A 26" bike tire is 26" tire and all actual rim size is 22" devide that by 3" = 7.3 ratio.

Different from motorcycle were the rim would be 26" if they made one..........Curt

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@CurtisFox

Question for you or any others that have an opinion on the matter. I was just thinking, using steel rims on my next build would be the better idea from what we've previously discussed. However after thinking on it a little more the following concern arose. I was thinking of using heavier gauged spokes on my wheels both front and back for added strength and durability. I've seen custom wheels I can order that have 11g spokes and come with drum break hubs. These are aluminum I'm almost certain. Can you get custom steel wheels? Also, what about custom wheels with larger spokes that are disc break ready? I really want HD wheels and would love to utilize disc breaks. Any recommendations on that? Thanks!