Coral Snake Cobb Job

[Mr. Gangrene Genes]

Greetings from Kansas City. Please consider this my belated introduction.
I am a hoarder. Come from a long line of hoarders, cars, trucks, lawn mowers, tractors, bicycles, what have you.
While I would like to be able to stay at home all week and tinker, I remain a white-ish collar slave to the MAN.
For the last several years my main summer transportaion was a high mileage 1987 Honda Aero NB50 scooter. Much cheaper than driving since I don't have to pay for parking or as much gasoline, and faster than the Metro bus while running on my schedule.
Last fall it suffered several set backs that caused me to lose faith in it and it got sold for the price of the replacement piston.
Didn't realize how much I would miss it. So I started digging in the war chest to build a motorized bicycle.

A friend gave me a bicycle like this that I started to clean up for my wife. She said her knee would not allow that foolishness.

Had an old Schwinn excerbike similar to this that I used parts off of for a 24" Stingray project. Started to make it into an electric trike, but that idea lost steam.

Along with some moped wheels for the drum brakes, studying old pre-WW1 motorbikes for ideas came across this Wagner.

Hack them up, and hot glue them together and get something like this.

 

[Mr. Gangrene Genes]

Added some crank pedals off a 24" Schwinn, a fork off a 26", with a 20" tire to match the moped tire diameter, seat off the Murray and viola a rider.

Felt like the front end was somewhat low so tried a 24" tire, much better.
For good measure put on a 26", nope too tall. Made a fixture jig to set the ride height.
Making a leading link springer fork with the floor stand and tabs from the excerbikes.

 

[Con-Tiki!]

that's pretty cool. The springer reminds me of the front-ends Greeves used on their machines...
Will you be able to get a tag for that ?, the laws in PA are really strict with regards to bikes/mopeds/scooters.

 

[Lilgti]

I dont know why this thread hasnt gotten more attention! Thats a rad frame you've built! cant wait to see the end result!

 

[NumbaFo]

Awesome build, keep going, wanna see more!

 

[Mr. Gangrene Genes]

Howdy, thanks for the kind words of encouragement. Most people that see it quote Star Wars “you came in that? You’re braver than I thought”. No license tags or insurance, Missouri is pretty lenient on scooters/motorized bicycles. The big one that put the kybosh on the Tecumseh in the first picture is the 50cc limit. I was irritated that none of my engine stockpile would be legal, bit the bullet and bought a GXH50 Honda 4-stroke. Have enquired with LEHR to see if they have a propane conversion in the works for it. No reply. Considered the 4G Gilmer tooth belt transmission, but none were/are available. The Honda is a high speed engine so there will be a 12 to 20 chain drive jackshaft as suggested by the guy at Max Torque. Over 16, valid driver license and an automatic clutch are a few of the other restrictions. That last item eliminates the Johnson Bar roto-tiller style activator I wanted to use. Currently trying an old Vari-plex variable width pulley, but have left my option open for a centrifugal belt drive clutch. While I am sure the local law enforcement has better things to do then hassle a middle aged guy commuting, the styling clues will all be bicycle, not motorcycle. In that regard and because one of the intermediate belt drives fouls the upper tube, the fuel tank will be mounted in front of the handlebars like a derny pacer.

 

[scrumblero]

thats genius!! this is what makes this site great!!

 

[masterpoop63]

DUDE THIS IS SWEET! 8)

 

[Mr. Gangrene Genes]

Here is the first attempt at engine placement. Actually second, had bent the lower tube to the left to clear the Tecumseh flywheel. Wadded it up badly trying to twist it over to the right for exhaust clearance on the Honda. Bending tube well is not one of my skill sets (yet). Usually find it simpler to splice together the factory bends from salvaged frames, hence the somewhat coral snake appearance. Not pleased with how high the engine sits in the frame. It is only 13 pounds, but want it as low as possible for center of gravity, clearance, and it just looks ungainly where it is. Worked on springing the fork, it is held rigid here with hose clamps. Like the looks of the Felt Abraham Linkage fork, but it would need to be lengthened and it costs money, something I have very little of. Kept trying to put the springs in front which would foul a fuel tank and a headlight. Finally I noticed all the space behind the lower triple tree and will put the springs from an office chair there.

 

[Mr. Gangrene Genes]

Cut out the raggedy lower tube and replaced it with part of a school bus seat frame & leg.
Looking less & less like a Wagner, more like a functional street fighter.
Pulley above engine is the upper jackshaft to multiply and route the power.
Wood is just the locating fixture jig. Using a go-kart front hub cut in half for the high speed bearing support.

 

[Mr. Gangrene Genes]

Made the office chair springs mount in the empty space behind the lower triple tree. Used 3/16 plate as large as would clear the frame, looked like owl eyes and the extra diameter didn’t really add much strength.
Decided some thickness would help the stiffness. Slash cut some leftover roll-bar tubing, bridged them together at the tall end and trimmed the plate down to their width. Steering head bearing cups are just the right size for the upper retainers. Had a castoff roller wheel from something that was mounted in a piece of channel. Don’t really enjoy drilling holes in steel, so cut the shape I wanted around the holes that were already there for the lower connetions.
Boxed the engine mount and got some 1-5/8 x.122 wall seamless tubing from FlashBurnFabrication.com a local company that was great to deal with. Used it for the two lower jackshafts and a half a go-kart hub for the upper. Going to have some friction lost in all the bearings, belts and chains. Ok, maybe not much loss in a proper fitted chain.

 

[Mr. Gangrene Genes]

Not much progress to report. Was torture testing the springer by standing on the engine mount and riding over chuck holes and the dip in the neighbors driveway. It was going really well, and then not so much. The springs started binding and the front fork had bent forward like a lowrider. Maybe won't have happened just riding instead of crushing it, glad it happened now instead of on the way to work. Also had a problem with the spring mount going over center and stuffing the tire into the lower triple tree. Straightened the fork a little too well, now it would over center with the slightest hint of a bump. Bent the tabs back farther than it started, about 45 degrees. Then the fork looked liked a chopper and the effective spring rate was sky high. Eased them back to about where they were to start and made a girder truss out of the old seat stays, more coral snake. Hope it holds.

Shot from the top that shows the spring plate a little better, that is a shim under the right side spring.

Need to work on the intermediate pulley and idler, as well as make some new rear axle plates. I am afraid the axle will pull out of square with the bicycle type drop-outs, even with stops.
Thanks for looking.

 

[Mr. Gangrene Genes]

Finally got back to the motor bike, spent all my time and money on the JEEP and it is still not finished, nor does the D4 Caterpillar run. Fellow is not too bright to spend all summer working on an open car and motor bike while letting his enclosed 4wd languish and fall out of license with winter knocking. It is what it is, make the best of it. Drilled and formed the flat bracket in the center and used a mower belt that was lying around, some zip strips to hold it together long enough to take a few rides. Pleased that it runs, marginally better than pushing the pedals. Somewhat disappointed in the lack of pep, some power loss over the scooter because it is a 50cc 4 cycle instead of the 50cc 2 cycle, half the power strokes. Think it is also over-geared since the motor doesn’t want to rev up under load. Ordered a 13 tooth sprocket to replace the 16 tooth final driver behind the aluminum pulley, hope there is chain clearance at the bottom bracket. More buzz in the pedals and grips that expected, not unbearable, just mildly annoying. Riding downhill, it appears that the centrifugal force on the heavy primary belt pulls it down into the adjustable upper sheave to make sort of an automatic overdrive, shall see if it really does work that way. Need to police up a few things and make a lever to remove tension on the idler when required, too much drag to pedal without the engine running. Would have been cheaper to fix the scooter and ridden it all summer.

 

[54shadow]

Shear genius!

 

[user 135]

A genius at work. Pretty crazy build and fun to read.

 

[nick_ish]

Whoa! Brilliant work love it! ;D

 

[Mr. Gangrene Genes]

Last Saturday I rode a few miles over to Ralph Wayne's Backyard Nationals. One of the best motorcycle shows you can attend if you are in our town the first Saturday of October. Really more of an "organic happening" with 100's of motorcycles swirling around the neighborhood like a bee hive. The cobb job was not booed or laughed at, really a warm reception for what shape it's still in. Took pictures of a bunch of motorcycles for my Dad who could not attend, forgot to take one of my own entry. Here is a website I found with just a small fraction of what was there. Not sure if the comment is satire or irony, they did feel strong enough that they took a photo of my mechanical novelty.
This Saturday I rode 11 miles over to Steve's Auto in Raytown for their annual Open House. Nice show on the lot behind the shop and they are friends from way back. Swapped the V-plex torque convertor driver for one with more range, the driven seems to be unresponsive to change in load. The 40 year old spring is probably weak. Also have not lower the gear ratio so it slows considerably going up hills. Lovely day for a ride and made it there and back. Knees were complaining somewhat on the ride home, may have to adjust the seat up.
Here is the referenced link, thanks for looking.

http://smg.photobucket.com/albums/v306/ ... 1QQtppZZ16

 

[Mr. Gangrene Genes]

Finally got a 13 tooth sprocket swapped in for the 16 over the weekend. Rode it about 11 miles to work yesterday in the spitting rain. Gear ratio change made very little difference in the hill climbing ability, however it did slow the descent speed. Many more hills than previous rides, painfully slow. Got passed by a Metro bus, how embarrassing. It is faster than pedaling my mountain bike, 50 minutes compared to 1:20. I surmise that the wider range variable V-Plex pulley was somewhat cruddy when first installed. Now that it is limbered up and properly oiled, the ramp angle is too quick for my application. With any engine speed much above idle, it moves the belt into a higher gear than it can pull. Still very much in the trial and error phase, lots of errors.
Swapped back to the smaller pulley in the photos, replaced the steel pan comfort seat with a springier item off an English racer 3-speed, and the Schwinn approved grips for some smooth black rubber ones. In my quest to make it look more bike like, failed to consider that the finger grooves would rotate with the throttle grip poking the palm. Raised the seat as high as this post will allow to ease the knees, too old to be totally addicted to style. Cobb Job motorbike is really pretty short with the moped tires, seat floats in space now. Not that you can tell with my bulk hovering over it.
Yesterday’s biggest mistake was forgetting the Number 1 rule; in a gun fight, it’s have a gun, on a gas powered device, it’s have some gasoline! Completely forgot to check the fuel level when leaving the house, got to push ½ mile uphill to the 7-11 on the way home. Current tank only holds 87 cents worth, about 15 miles to the cup. Lost a lot of enthusiasm for the project, got some back when it started and made it the rest of the way.
The short chain from the engine to the jackshaft is throwing all the lube off very quickly. Soaked it in gear oil lasterday and it still went dry. Swapped out the high speed bearing that takes most of the load on the jackshaft. Hope it was my poor installation or a defective part because changing that every week or so will get tiresome. Suspect the speed is too fast for the Tractor Supply chain and standard bearing, may have to step up in quality. The rear chain seems to be holding up well. Have not made new rear drop outs, axle has not pulled out of alignment yet.

Won’t be getting much accomplished in the next few weeks. Have plans to build a pedal powered carriage for the Independence Halloween parade.
The main idea is “What if the Child Catcher from Chitty Chitty, Bang Bang teamed up with Prof. Fate from the Great Race and had him build a new collection van?”. Front wheel drive with some cast off 10-speed wheels mounted on swivel bogies in the back. Hello kiddy winkies, I know there are children here, I can smell them. Free Candy & Ice Cream today!
Why do my best ideas involve putting my 5 year old in a cage?

 

[Mr. Gangrene Genes]

I worked toward the 5-wheeled carriage but didn't make much progress and missed getting to ride in the parade. Oh well, there will be another one next year, start a little sooner for 2012.
Beginning to think the jackshaft chain on the Cobb Job is a fatal design flaw. A 12 tooth sprocket with a 1/2 inch pitch chain seems to me as 6 inches. At the top governed engine speed of 7200 rpm, half would be 3600 feet per minute, or about 40 mph chain speed. Reading some roller chain manufacture specifications, they consider anything over 1500 fpm as "high speed" requiring an oil bath or at least a directed oil spray. Have emailed the gentleman at Max-Torque who recommended this set-up, Jim I think. Have not received a reply if anyone has used the jackshaft scheme for more than a display. Have less than 100 miles on mine and the chain is toast, including the master link. Perhaps a better quality chain will suit, or perhaps a Gilmer tooth cog type belt would work. Emailed Gates about their CarbonCog bicycle belts to see if they would stand up, no reply yet. Don't think I will.
Riding this project as daily transportation seems to be a lost cause at this point. Weather is nice today but can't last much longer. May have to pickle it and try again in the Spring.
Did find a cool fuel tank in the war chest, probably too nice for this project. May still make brackets for it, can always install it on another in the future.

 

[Mr. Gangrene Genes]

Well I did mount the Briggs fuel tank, also used one of Dad's old aluminum lunch buckets to hold a pair of batteries. The lid has enough clearance to run the wires with out drilling holes or bending anything. One battery for the halogen headlight, one for the taillight I stuffed full of LEDs. Should have wired one to the engine kill to have a running light, with the rest wired to a brake light switch. Live and learn, may change it later. It is somewhat cluttered, not really sold on it. Changed the cable controlled brake to the front, and made sort of a rod activated emergency brake for the rear. Looking around for a lever to use and thought that it would need a bend and a knob. Then I spied a tire iron that meet all the requirements. The pivot and angle is not quite right, takes up a lot of the slack before engaging the brake. Hard steel, difficult to drill, ruined some bits. May have to bend the lower a bit to make it right. Think I am going to give up on the 50cc legal engine for this project, not really working as planned. Probably re-do the lower mount and use a Briggs or Tecumseh. Since this will be mostly used to cruise around tractor shows or fairgrounds it doesn't need to be legal. Plan to use the legal engine for a lighter weight, somewhat more normal bicycle. OK, more of a motorized cycle-truck.