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DIY Home Built Motorized Bicycle (non kit) Post all about your home built rides here. Weedwacker motors, lawn mower engines ect. This area is for non kit builds


Pre build: weed eater advice

Post all about your home built rides here. Weedwacker motors, lawn mower engines ect. This area is for non kit builds


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  #1  
Old 03-06-2012, 06:28 PM
missle3944 missle3944 is offline
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Default Pre build: weed eater advice

Hi guys,

While I'm waiting on some torx bits to get the plastic housing off my trimlite weed eater 25cc engine I want to run my psuedo design by you guys and see if you can give me any advice or similar.

What thickness metal do you recommend? This seems to be the easiest design I can do right now becuase it requires no drilling into the frame. I plan to put a bmx peg on the shaft. I'm going to go friction drive and this is my first build. I cannot fit a 2 stroke in my frame and I'm a little tight on money. I have this weed eater engine lying around so I might as while put it to use!

The bike with it:

http://i.imgur.com/TIcAU.jpg

Regular:

http://imgur.com/ElOhW
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Old 03-06-2012, 11:06 PM
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BigBlue BigBlue is offline
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Default Re: Pre build: weed eater advice

Hi Missle,

here's mapbike's project that might fit your bill. It is simple and doesn't require much money to build. Check out some of the other members friction drive projects - no need to re-invent the wheel.

http://motorbicycling.com/showthread.php?t=33199

Good Luck

Chris
AKA: BigBlue
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Old 03-06-2012, 11:11 PM
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Default Re: Pre build: weed eater advice

I'd go with no larger than an 1 1/8" drive roller...
Good luck
rc
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Old 03-07-2012, 11:00 PM
missle3944 missle3944 is offline
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Default Re: Pre build: weed eater advice

Looks relatively simple, though I don't have a drill press to drill through that solid pipe.
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Old 03-09-2012, 02:41 AM
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Default Re: Pre build: weed eater advice

Off topic:

All the kids around here ride those tiny-framed bikes, but I've never seen any of them without the seat lowered all the way. Even the 6-foot tall teenagers are riding way down low with their knees bobbing up by their foreheads. Must look "cool". It's good to see in your pic that someone knows how to raise a seat to a useable level.

On topic:

Rustycase is right. An inch-and-an-eighth is a great roller diameter to start with on a wacker-powered bike. Small changes make a big difference. Over 1 1/4 means no torque. Under an inch will give a top speed under 20 mph.

You'd be amazed what you can do with hand-tools and determination. I used to clamp my ancient 3/8 inch drill to the benchtop with a wood-jawed handscrew clamp and use shims to get the drill bit parallel with the benchtop. Then I'd feed the material by sliding it on the bench into the stationary bit. You can get some really accurate drilling that way, but it is a pain to set up, of course.

What thickness metal? What part? Eighth-inch thick steel will be strong enough for just about any part on a well-engineered MB. Aluminum is a lot easier to work with hand tools. Impress us by making all your parts out of bamboo, wood, or paper-mache (and JB weld, of course).
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Old 03-09-2012, 10:13 AM
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Default Re: Pre build: weed eater advice

I'm hoping Deacon will join this dicussion. When it comes to friction drive he knows what he is doing. If he suggests you do something. It's a good idea to listen to him.
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Old 03-09-2012, 09:29 PM
missle3944 missle3944 is offline
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Default Re: Pre build: weed eater advice

Thanks for the feedback guys. Another question is how do I mount the peg on the shaft? do I just jam it on there. I don't have access to a welder either. Could I use plywood?
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Old 03-09-2012, 09:54 PM
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Default Re: Pre build: weed eater advice

IMO... :-)

I think you could cut out a bunch disks with a cup saw and stack 'em on a shaft with some of the hi-horsepower glue now-a-days to laminate 'em and probably run for quite a while.

IIRC, it was Cannonball2 who experimented with wooden rollers, and results seemed to be promising... but I'd ask him, or run a search on wood rollers and see what comes up.

...otherwise... some of the bmx freestyle pegs will thread on to some of the string trimmer output shafts, OR, a washer may be dropped down inside the peg, and a suitable nut tightened up on the shaft to hold it.

I have a friend who is an accomplished gunsmith with a full blown machine shop... SO, every so often I try to 'stump the machinist' and drop my oddball projects on him... He shaved and turned down one of my Mac flywheels and made me an aluminum spindle, complete with a bearing on the outboard end.
Nice fellow!
...He grumbles every time I show up! Wonder why??? :-)

If you do not have the facilities to do some sort of work, may I suggest a high school or college machine shop class? They are generally open to interesting projects and may take it on, if yer lucky.
Of course you will be required to pay for materials consumed, but labor is gratis, IME.

Best
rc
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Old 03-10-2012, 12:43 AM
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Default Re: Pre build: weed eater advice

first, take your motor apart and find out what kind up shaft you have - short or a long shaft. From there, you can determine how to mount a BMX foot peg to the shaft or make your own.

Do a search on what others have done and you'll get a better understanding of what to use as a roller, how to mount the roller and what kind of materials work best for rollers. Also would give you some better ideas how to cheaply make your mounts without spending much money or having many tools.

As rustycase stated, you could make your own wooden discs and glue them together with a clamp and run a bolt down the middle. You would have to be accurate on your drilling, so the roller would run true. Don't know if it would work until you get the motor apart. Others have glued 80 grit soft backed sand paper to electric motors for traction - might work on a wooden roller.

Good Luck,

Chris
AKA: BigBlue

Last edited by BigBlue; 03-10-2012 at 02:35 PM. Reason: Shafts - rollers - I am confusing myself?
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Old 03-10-2012, 05:34 AM
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Default Re: Pre build: weed eater advice

Quote:
He shaved and turned down one of my Mac flywheels and made me an aluminum spindle, complete with a bearing on the outboard end.
It's funny you said that, because that is exactly what I just did about a week ago - and it's for my Mac motor too!

I trimmed the flywheel fins and made a 5/8 OD aluminum spindle to go over the existing shaft. Would have been about a 15 minute job if I had a lathe. And the McCulloch's shaft is about 0.365 inch, so a 3/8 bore would be too loose (my Homelite's shaft was a standard .375 - three-eighths). I also threaded it because there's more than 1/4 inch of threads past the flywheel nut. It was a pain, but it's going to work good. There is more than 3 inches of spindle for me to mount the friction roller and have the outboard bearing at the end. I'll post pics when I get around to it.
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