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31cc YardMan In Progress!!!

miletwo

Member
Joined
May 2, 2008
Messages
38
I finally got the piston into my Yardman and started mounting the motor to the bike. I realized this morning that it's on backwards, but the beauty of the design is that it's reversible. I'll be moving it to the other side, finishing the support and adding a skateboard wheel as the friction drive hopefully all this week. Goal is to be riding it to work on Monday.

<p><a href="http://picasaweb.google.com/miletwo/YardMan31ccWhizzer/photo#5208423022931484002"><img src="http://lh5.ggpht.com/miletwo/SEgJJNnMHWI/AAAAAAAAAWs/NKXkVA5Dygw/s144/1.jpg" /></a> <a href="http://picasaweb.google.com/miletwo/YardMan31ccWhizzer/photo#5208423027557938882"><img src="http://lh4.ggpht.com/miletwo/SEgJJe2ONsI/AAAAAAAAAW0/3gjZNUQNMYQ/s144/2.jpg" /></a> <a href="http://picasaweb.google.com/miletwo/YardMan31ccWhizzer/photo#5208423031630431570"><img src="http://lh6.ggpht.com/miletwo/SEgJJuBLhVI/AAAAAAAAAW8/16lVA1VR7Yo/s144/3.jpg" /></a> <a href="http://picasaweb.google.com/miletwo/YardMan31ccWhizzer/photo#5208423033475454802"><img src="http://lh4.ggpht.com/miletwo/SEgJJ05EV1I/AAAAAAAAAXE/Y6m45Ie7gJ4/s144/4.jpg" /></a></p>
 
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miletwo

Member
Joined
May 2, 2008
Messages
38
Haven't exactly figured it out, but I'm thinking about using a skateboard wheel. I'll only be driving when it's dry, so I'm hoping grip won't be a problem.
 

rossfree

Member
Joined
Jun 4, 2008
Messages
71
Looking good Miletwo,

Simple rocks! Couple of comments...

Size of the drive roll might matter. I like the idea of using a skateboard wheel. Off the shelf... easy to replace. But the diameter seems large?

5000 RPM x 2 (aprox std skate wheel) x 3.1416 x 60 / 12 / 5280 = 29.5 mph. I don't know the top-end RPM of these motors... anybody?

Still I like off the shelf! Have a hub turned that allows nice bolt-on fit.

I see what looks like a 1" sq tube pivoting on maybe a 3/8 - 1/2" shaft. Do you intend to add a second member on your pivot shaft? That would be my suggestion. The holes on your sq tube would hold for a while but there could be some reasonably significant forces on that 1" moment arm. A second member on your bolt would frame it up nicely and eliminate that concern. (You were probably going to do this already... just looking out for you :)

Keep us posted with pics! Looking really sweet!

Ross
 

miletwo

Member
Joined
May 2, 2008
Messages
38
Thanks,
Size of the drive roll might matter. I like the idea of using a skateboard wheel. Off the shelf... easy to replace. But the diameter seems large?
I have small-ish skateboard wheels around that are about 1 3/4" that I'm hoping will work out. The goal is to create a spindle that will bolt on to the output shaft that will easily accept a skateboard wheel then I can easily replace. Once I get it finished I'll be sure to report on speed and try a few wheel to see how they roll. (ha.... roll...)

Since this will be friction with no clutch, I'm going to be giving it all of the starting power from each stop so low end is less important to me. I already ride this bike to work without power so I'm just looking for a little cruising assistance to help me in the 10 mile commute.

I see what looks like a 1" sq tube pivoting on maybe a 3/8 - 1/2" shaft. Do you intend to add a second member on your pivot shaft? That would be my suggestion. The holes on your sq tube would hold for a while but there could be some reasonably significant forces on that 1" moment arm. A second member on your bolt would frame it up nicely and eliminate that concern. (You were probably going to do this already... just looking out for you :)
Indeed I am about 1/2 way through the support framing. It's actually 3/4 tubing and 3/8 pivot. The part that scares me more is it's only mounted to the forks with a single 1/4 bolt through the fork. I'll be re-engineering that piece before I go prime time. I'll also be adding another shaft to the other side of the pivot point which will be braced between with another piece of the square tubing. Partly for more support, but also partly to keep the engine from moving side to side as well. I'd really like to make this whole setup easily removable and perhaps quickly relocatable to the rear wheel or another bike, hence the reverseability.


Here is what I expect for final design:
<img src="http://miletwo.net/temp/bboard_post_files/engine_support.png" />

Thanks for the encouragement.

Jeremy
 
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S

SirJakesus

Guest
Couldn't you make the frame mount a bit longer and add a bolt at either end? It would be maybe a bit clunky looking but much stronger if you're worried about the bolt shearing off. I would probably prefer rear mounting the engine if possible as well unless you're planning on carrying cargo on a rear rack. Neat stuff anyways, cool to see somebody design their own.
 

miletwo

Member
Joined
May 2, 2008
Messages
38
Yea, I'm working on alternate mounting instead of the single bolt. I'm trying to make everything as "quick-release" as possible so it will likely be some kind of folding or hinged design.

You guessed exactly right as to why I'm front mounting and it's because I intend to drive the snot out of this thing to work and I will be carrying my laptop and lunch every day.

The last part of the reason I'm designing and building my own is $$. I'm into this for only $60 and it's done.

========================
Yardman trimmer off craigslist - $10
New Piston/rings - $30
Metal/mounting hardware - $13
Throttle cable - $7

Not paying $40/week in gas... do the math... almost priceless
 

miletwo

Member
Joined
May 2, 2008
Messages
38
I finally got it all finished last night, including ghetto-fabbing a throttle out of the old weed wacker throttle. I'll be tossing that and using a brake lever or thumb throttle in the near future but this works for now. It's still raining here (as usual) so I haven't been able to test it out, but attempts at turning it over in the garage were unsuccessful. Since I rebuilt the motor with brand new piston/ring the compression is quite massive and until I get a bit of gas introduced and run it a bit it's going to be tight.

I'll get pics up tonight. The skateboard wheel seems like it's going to work well.
 

onij

New Member
Joined
Jun 10, 2008
Messages
10
Thanks for your help on my other post miletwo. Your bike looks great. You live in Portland too?
 

miletwo

Member
Joined
May 2, 2008
Messages
38
No worries... you're quite welcome.

I live in East Gresham off of Orient Dr. near Mt Hood Hwy. I built the motor add because I wanted to start riding it to work off 84 at 181st. It's about 10 miles and quite a bit of hills and although I don't mind pedaling I'd like a little help on the hills.

Cheers, and welcome again!
 
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