Making a custom bike engine

[Mitchg95]

Hi all, I am new here and I am learning to be a machinist, I have two years so far running manual machines and a little cnc experience. Any way, I am in the process of designing a 6 cylinder inline engine using the cylinder/ piston sets that are available for the 66cc bike engines. I have a few questions about these engines, as I do not own one yet.
Can someone give me a few simple dimensions ie: cylinder/head length and width, and hopefully someone can tell me what the stroke of these engines are.
I am planning todo the crankcase in seperate parts that bolt together with plates inbetween the case segments that will seal up each segment of the case and will have the bearing hole for the crank shaft.
I am able to use the machines at school to make some of the parts next year but it is summer but luck would have it that my neighbor a few houses down is a machinist with his own shop in the garage, so maybe he can help me out with some parts. thanks
Mitch

 

[Theon]

Bore 47mm
Stroke either 38 or 40mm.
How do you plan to connect the crank assemblies?
Sounds like an interesting project.

 

[maniac57]

Why not scale back your aspirations to something more realistic, like machining a custom crankcase for building a REAL bicycle motor. Cut yourself a set of cases the allows you to use a real quality crank from a moped or motorcycle combined with one of the hot moped top end assemblies with the single speed manual clutch from the HT.
While building a running 6 cylinder engine from HT's is entirely possible,I would have to say it is very unlikely to succeed as a first machining project during school....
A set of billet custom cases using existing moped and HT parts however would be a great first project involving nearly all aspects of machine work.
Talk to your instructor and see if he agrees with me.

 

[Mitchg95]

I am not sure yet on how I will go about this, a thought that I had is if I made the partitions that go between the case segments, If I made those out of two parts that bolt together so I could install the bearing on the shaft, then put the shaft between the halves, and bolt the halves together.
Thanks for the bore and stroke information. Ive started drawing out a front view of a case segment.
I need to find out at least, the width of the cylinders so I can set a outside dimension for the case. Ive decided to offset the cylinders at 45 degrees to help with cooling.

 

[Mitchg95]

Maybe a 90 degree angle would be better for the angles of the cylinders? What do you guys think?

 

[Theon]

I've always liked the idea of a flat twin, as made for model aircraft.
with a dual plane crank so that both cylinders fire together.
I agree with Maniac.
A custom set of cases for some better quality parts would be much better.
The outside width of these barrels can vary a little but are generally around 100mm.

 

[maniac57]

Colorado...
this explains a lot.

 

[Gawdzahh]

Machine a V-Twin bicycle engine....

 

[Mitchg95]

It's going to be a flat opposed engine, I had to rethink some things and the previous design would not have worked due to Clarence's and what not
Can someone tell me the mounting dimensions for the cylinder?
I might order some parts tomorrow to aid in the design
Mitch

 

[Theon]

bolt hole spacing is 64mm across the diagonal.
Hole in cases for barrel 52mm.
from crank center to barrel base 60mm.

 

[Theon]

I want one too!

 

[Mitchg95]

Thanks for the measurements Theon!
Those really help a lot! I'll do some more drawing tomorrow. What I have so far, is the shape of the case is going to be in the shape of a capital H with the cylinders on the ling sides of the h and recesses milled into the case to make the shape to help lighten it up a little and also for mounting purposes
I'll try to post pics tomorrow

 

[Theon]

you want the pistons to run longitudinal to the frame otherwise the motor will need shaft drive and interfere with pedals.
Barrels will need to be offset by thickness of the center crank flywheel.
I studied diploma of mechanical engineering 20 years ago, and was good with CAD then, but have not used it since, otherwise I'd draw up a few Ideas for you.
Still I might sketch up a few things.
I have an old shaft drive quad rear end that would be fun to do something like that with a transverse mounted boxer.
There is a thread here somewhere where a guy has an inline boxer in a pushbike frame.
What I would really love is a morgan style cycle car with a boxer twin mounted up front.
Have a look at a DLE 111 twin.
http://www.ebay.com.au/itm/DLE-Engi...Accessories&hash=item2ed1f735e7#ht_4179wt_937

 

[Theon]

To make it really bogie, Id be going case induced with a DLE reed.
If you could make it mount to seat post?

 

[Mitchg95]

How thick do you think I should make the center cranks?
I understand what you are saying about running longitudinal with the frame, would I be able to mount it so that instead of the cylinders stick out out side of the frame, I could mount it so the cylinders would me vertical (and have the case) horizontal to the top tube? Just thinking.
Mitch

 

[Mitchg95]

Stupid question, but if the cylinders have the intake and carb mounted to them, how would the reed work?

 

[Theon]

Block off the inlet ports, case induce it, like the DLE.
Make the inlet a third transfer port.

 

[Theon]

Center crank flywheel would probably only need to be 10mm.

 

[Mitchg95]

Ok, I think I understand now thanks for the pictures

 

[Mitchg95]

Where is the, absolute cheapest I can find a 66cc cylinder, and bare crankcase (I only need half of one)? Thanks