99cc rack mount 3 speed spoke drive MTB

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cannonball2

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Oct 28, 2010
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I don't understand why two pulleys welded together is necessary... to make it stick out further to the side? To avoid interference from the bike frame? Is that it? Must be. If the center of the outer pulley was opened up wider then access to the C ring might be better. Weld the pulleys together at the outer edge.
SB
Sorry its a bad idea! It might have gotten the offset but there is not enough axle to do it. It seems the simplest thing is to off set the engine. I know you dont want to but it will greatly uncomplicate things. Replace the two mounting bolts on the rack with one long bolt or rod to set things up. Get the hub mounted then you can set the engine on the rack to set the belt line. Once the offset is established you can make spacers from tubing/washers to lock in the offset. Then we can determine the belt length and you can drill the engines mounting holes. This will eliminate a complicated jack shaft. The offset probably wont be too bad.
 

silverbear

The Boy Who Never Grew Up
Jul 9, 2009
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I don't know, I was starting to kind of like the double pulley idea. I think the engine offset will be okay. With just the clutch pulley hugging the engine on the right and a good bit of stuff on the left (flywheel & pull start assembly) it will actually be more balanced offset a bit and I don't think it will take much. As you say, get the hub mounted and then align the engine accordingly. One reason I'd like to move the engine forward some is the front to back weight balance of the bike and all that torque coming from the back. You made an observation early on in this thread about wheelies and hill climbing. Visions of lying on me back taking inventory of what is and isn't perhaps broken in this old body... well, the old bear doesn't need that! Keep it upright with tires on the road and putt putt along with dog in tow, both of us smiling. Yes...

I should know a bit more by day's end. It may not be what I wanted to learn, but I'll at least have some idea of what is next.

Curt, whenever you have the time, I think we should go ahead with the 6" pulley welded to the hub sprocket.

Thanks to both of you guys for the guidance.
SB

CB2, I just realized you mean the other way on the offset of the engine. Still, I don't think it will be by much and if it is then there is some brilliant solution one of you guys will think of, having to do with a jack shaft, no doubt. Ha! It's all part of the fun.
 
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cannonball2

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Oct 28, 2010
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SB hold off on pulleys at this point, until you get a belt line established. If a jack shaft is necessary then the 6" pulley should go on it and not the hub. A 6" pulley on the hub will require fairly long hub mounting arms. Lets not build those unless we have to.
Just move the mounting rails over and test fit the engine with an estimated offset and see what it looks like.
 

curtisfox

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Dec 29, 2008
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I thinking of your rail mount I had trouble with mine moving or slipping,that being said take like a good 1/2" thick plate and drill it to fit in place of the one on there,that is on the inside of the frame.
Make it long enough to mount jack shaft bearings on under the stays. Then you could put the pulley inline with the engine and one inside inline with the hub. Have slotted hole for the engine and for the hub.
Also find a old long belt and cut it to length put a couple staples in it,then the hardware store can put it on the machine and get the right length.

Just my thoughts........................Curt
 

silverbear

The Boy Who Never Grew Up
Jul 9, 2009
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Well, that isn't going to work, so back to the drawing board. First there is a lot of engine offset and I still don't see it working with bike frame members in the way of belt alignment. It just doesn't work without a jack-shaft and even then the bike frame is in the way.

So, how about this? The engine goes as far forward as it can. Behind the engine are side mount jack-shaft bearings to carry the two pulleys. Near the tail of the right side rail the top is cut out to make room for the inner pulley on the jack-shaft. Arms are bolted to the sides of the rear portion of the rails and that is where the 3 speed hub is located under the rails. Engine is centered. As I see it, the issue is whether or not there is enough distance between pulleys for the belts to do their thing. What do you think? I don't see another way to do this. The rail supports I made yesterday would need to be moved to make room for the pillow blocks. Where the jack-shaft is sitting in the photo would be moved back a little.
SB
 

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silverbear

The Boy Who Never Grew Up
Jul 9, 2009
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So you were seeing the hub mounted off of the seat post and making up the mounting plate so the pillow blocks would have belt clearance, is that right? One way or another it looks like there has to be a jack shaft.
SB
 

curtisfox

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Dec 29, 2008
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Yep pillow block to give room for pulley to the hub maybe have to shim it out some depends on the pulley size, But like CB11 says put the bigger one on out side jack shaft......Curt
 

silverbear

The Boy Who Never Grew Up
Jul 9, 2009
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The rails feel solid to me with everything bolted down tight. I don't see alignment issues with the way I have it laid out with the hub drive in back. Alignment with the hub in front is more of an issue because of the bike frame. There just isn't much room.
SB
 

curtisfox

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Dec 29, 2008
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Yep should work good that way also,you may have to cut the right rail for belt clearance to the hub on the inside,but no biggy .............Curt

PS all the pulleys i have are for 3/4" shaft,3" and 4" i think
 

silverbear

The Boy Who Never Grew Up
Jul 9, 2009
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Hi Anne,
I don't know if all the problems are solved, but it's fun exploring the options. I didn't work on the hub mount today, not knowing for certain if the drive hub will be on the seat post or
at the tail end of the rails. I'll get the engine first and give some time for thinking about and staring at.

Today, in between cutting firewood sessions, I worked on a new drop stand. Copper again but made stronger by having certain areas double wall and making the footprint a good deal wider. It will be more stable than it was and hopefully will keep the bike upright. Being somewhat top heavy, tipping over is a concern, so I gave it priority today and will solder it up tomorrow to have it on the bike and ready for the engine. Better to do it now instead of waiting for it to fall over first.

Yes, this is a wonderful community of people. I'd be lost without "a little help from my friends".
SB
 

silverbear

The Boy Who Never Grew Up
Jul 9, 2009
8,325
670
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northeastern Minnesota
The drop stand is done with the exception of a couple different length bolts than what I'm using. With the extensions which were inspired by canoe and kayak outriggers it seems to be quite stable. Stylish, maybe not, but obviously this bike is not trying to look like anything in particular beyond motorized bicycle. Function is number one.

Now I can set the engine in place without worrying over it falling off. The engine arrived yesterday afternoon and today I'll attend to it's needs. In looking it over I've decided to leave the muffler alone. Gas tank is fine where it is. I may change the clunky air cleaner to one made from a tuna fish can to give more access room to where the jack shaft will probably be located. The governor needs to be removed and the throttle set up for a twist grip one from a China girl kit. Add oil to the crankcase and the engine can be fired up.

After that, final decisions need to be made on where the jack shaft should be located. Then drill the holes for mounting engine and jack shaft pillow blocks and the mount for the hub drive. After that set up the shift control. I have one from a Shimano hub and a 1960's twist grip type for a Sturmey archer hub which is the one I'll probably use if the cable I have will fit it. I'll need some kind of catch for the drop stand in the elevated position and... whatever else I can't think of right now. Not much, I think. Belts for the pulleys.

No prediction on when it will be ready to ride, but soon I hope as it is that time of year. Buds are swelling up on the maple and birch trees, June berry and choke cherry bushes. Loons and Bald Eagles have returned to the forest along with the first mosquitoes and wood ticks to spoil the fun. After the very real hardships of a long, dark winter spring comes and goes overnight and suddenly the glory of summer in the lake country is here. Fishing opener is a week from today, which in my part of the world is like the super bowl, world series and basketball final showdown all at once. It is a rite of spring to go fishing even if the lakes are still too cold for much anything to bite. And even if it snows or rains, the faithful will gather on the thousands of fresh water lakes to baptize minnows, leaches and night crawlers as offerings to the season and to the spirits of the waters.

Since this is my thread, I give myself permission to tell a little story of sorts. Some years ago I worked for an Indian family who bravely adopted twelve Ojibwa children with disabilities, most of them from fetal alcohol syndrome. I lived with them as a kind of mentor, teaching them things about Indian crafts and how to swim, dive and such. One day we were at a lake to go fishing and I was checking on the bait box to assure myself the night crawlers were alive and well. As I checked, a couple of my little shadows helped look. I don't know what compelled the fib, but I held one up to look at closely and I asked them if they knew why they were called night crawlers. They didn't know. By now there were seven or eight of the kids looking on and listening. "You have to look very closely to see where their eyelids open and close, because they can't stand bright light. It hurts their little eyes, so they only open them at night when it is very dark. And then they can open their eyes and look around to see where they're going. And then their little legs come out. See here? It's hard to see, but they have four little legs that come out so they can crawl around. Can you see where they come out?" By now all 12 kids were interested and holding a night crawler. A couple of them saw the eye slits and tiny leg holes. That made it easier for a couple more to spot them, too. Add one more to the list of life sins... lying to innocent children.

I felt kind of guilty about it and never did set them straight. After all, I was an adult (by all appearances anyway) and they mistakenly trusted me. I'm bad. It still makes me laugh, though.

Now, back to our regular programming.
SB
 

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cannonball2

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Oct 28, 2010
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Cool story and nice engine SB! Turn it around if you want to go forward. Gonna need and elbow for the muffler! It is possible with enough belt run to reverse rotation with a twist leaving the engine in that position. Maybe the jackshaft at the very end of the mounts driving the hub mounted below it? Hang it from a swing arm to about the tires mid point and add a means to tension it(springs would work ok from both sides of the racks struts).
 

silverbear

The Boy Who Never Grew Up
Jul 9, 2009
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northeastern Minnesota
Thanks, Anne. Engine might look even better turned around the right way. Unbelievable that I've done it again. My lame excuse is being very tired from undergoing a colonoscopy yesterday at the hospital. Don't have to do it again for five years, yay!

Yeah, CB2, going forwards is easier for sure. I laugh, but I'm not sure it's funny if this is an indication of things to come. Ah well, that's why I'm here on the forum so you guys can straighten me out when I'm going the wrong way. I had to make up an exhaust manifold for the 99 predator so I guess I can do it again. I used a cast iron plumbing street elbow and welded it onto the remnants of the flange part of the stock manifold. I'll probably do as you did on one of your other builds and use a China girl muffler on it. Or, whatever works. Think I'll knock off for the day before I drill a hole in the tire or some other amusing thing. Jeez... sometimes I wonder about me.
SB
 
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cannonball2

Well-Known Member
Oct 28, 2010
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Don't feel bad SB. Im so tired from all the upheaval in my life that I had to look at it a bit to be sure it was backwards! Things can be confusing at times especially when mixed with fatigue.