Designing a crank case

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Mitchg07261995

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I am working on a concept for a 4 cylinder inline engine that uses 30.5cc cylinder and piston sets from HPI baja 5B model car engines. These engines put out almost 4hp on there own but any way, i would like to make a crank case to tie all 4 cylinder and piston sets together to put in the frame of a custom motorcycle that I plan to build to resemble the 1911 Peirce 4 which had a 4cylinder inline engine of 700cc but only pumped out 4hp.
Can anyone give some tips on how I should go about designing this case?
here is a Pierce 4 that I want my end result to look like
OMhwNtIl.jpg

mvUyYXJl.jpg

BJ9QL7Il.jpg
 
Do you think you will get enough torque out of those little engines? Even then having 4 high reving two strokes will not give the same effect as a thumpy old 4 stroke

J
 
I have never been interested in motorbikes, but that one is brilliant. Nice choice.
My only criticism is the swept back bars.
 
Multi cylinder engines using two stroke jugs are not uncommon. The individual cases are just bolted together in most cases.

https://www.mtc-powerboat.de/index.php?section=23&lang=en&produkt=51&detail=51

If the intention is to convert to fourstroke, I'd say start from scratch. If you want a 4 cylinder two stroke, just gear it accordingly. The most challenging part will be making the 4 throw crank and pressing it together straight with all the rods and bearings installed.

CRANKSHAFT_PISTON.png
 
Hi Mitch,

looks like You want to go a hard way. I can't give You much real advice, just a few tips. And I dunno these HPI baja sets.

1. Till is right, converting these cylinders to 4 cycle doesn't look promising. Besides many other problems, 2-cycle cylinders/pistons are designed to have some blow-threw to get some lubrication to the crank. Something 4-cycles shouldn't have. If You don't want to build a 2-cycle motor, forget these cylinder sets.

2. Make the crankcase as stiff as You can. The crank too.

3. At minimum You will need a 3rd bearing between second and third cylinder. 5 bearing may be better.

4. You will need to use a method of inline boring to machine those 3 or 5 bearings. Or a high precision CNC mill to do it.

5. Be extremely cautious when designing the crankcase. Its easy to overlook collisions there when parts are moving. Design it in 3D, and check it again and again for collisions. Then generate 2D drawings and study them carefully for any collisions. Do this before generating chips.
What materials for crankcase and crank?

6. Because the torque of the high-speed motor is much lower, You will need a gear reduction. Any plans, how to build it and where to install it?

Mike
 
Your going to have to keep the bicycle frame in mind as well... they'll have to mate nicely.

I'd say pick out a crank stroke to match the cylinders/pistons you have and go from there keeping the tube frame and mounting points in mind.

I hope you actually build this! That will be freakin awesome!
 
dieselpilot said:
Multi cylinder engines using two stroke jugs are not uncommon. The individual cases are just bolted together in most cases.

https://www.mtc-powerboat.de/index.php?section=23&lang=en&produkt=51&detail=51

If the intention is to convert to fourstroke, I'd say start from scratch. If you want a 4 cylinder two stroke, just gear it accordingly. The most challenging part will be making the 4 throw crank and pressing it together straight with all the rods and bearings installed.

CRANKSHAFT_PISTON.png
Click to expand...

I plan dont plan to convert to four stroke, I am leaning towards the idea of using 4 stroke cylinder and piston sets
 
Yes bolting four single-cylinder crankcases together, or two twin-cylinder cases together is eminently do-able.
Take a look at old mate Millyard's multi-cylinder creations. All done in his shed, with a hacksaw and file!
Google Allen Millyard for more info.

Remember the Kawasaki two-stroke triple? Count the pipes:


And the straight-four Kawaski four stroke?
Bit of hacksawing, filing, welding and pressing together of crankshafts and:
 
Allen's work is truly amazing to say the least! :) if I do do this, i am definetely planning to do this in say a 4 piece block like mentioned here.
BastelMike: thanks for the tips. I will most likely be making this in my machining class at warren tech next year in lakewood colorado, next year is my second year there and I get to learn how to use and program a cnc machine, in my class we have 2 vf1's a vf4 and a sl10 along with a haas mini mill.
 
Mitch my suggestion is find some plans for a 4 cylinder in line aicraft engine that has pistons the same size or close to the pistons and heads you have.
Remember I said said size not scale. maybe two or three sets. this will give you an idea of what needs to be done.
there have been some cool ac engines built of this type so I expect there are some plans out there.
Tin
 
Where might I find plans Tin for an engine of 122-250cc of an inline 4? I know where I can find plans for an inline 4, but the engine is only in the 10-20cc range if that
 
250cc is awfully big for a model engine. even large 4's like the panther pup and cirrus are only around 40cc. You are looking at a 1-3/8 bore and stroke just to get to the bottom of your range. I cant think of a set of plans for something that large. You might have to start drawing one up.
 
I agree with much of what's already been said. Especially where the use of multiple crank cases is concerned. But if you are looking for something that resembles the Peirce you might consider using components from Villiers engines as used in old lawn mowers.

they are basically the same 97-98cc units used in the pre-unit lightweight motorcycles of the late 1950s as they are very simple and can be picked up for very reasonable prices.
 
Just looked up the villier's lawn mower engines, i like the idea. Ill start looking for a used one on ebay to look at and plan further
 
Mitchg07261995 said:
I am working on a concept for a 4 cylinder inline engine that uses 30.5cc cylinder and piston sets from HPI baja 5B model car engines. These engines put out almost 4hp on there own but any way, i would like to make a crank case to tie all 4 cylinder and piston sets together to put in the frame of a custom motorcycle that I plan to build to resemble the 1911 Peirce 4 which had a 4cylinder inline engine of 700cc but only pumped out 4hp.
Can anyone give some tips on how I should go about designing this case?
here is a Pierce 4 that I want my end result to look like
OMhwNtIl.jpg

mvUyYXJl.jpg

BJ9QL7Il.jpg
Click to expand...

If I was going to build something like this then first off I would draw the entire bike in Autodesk Inventor, SolidWorks or Alibre (Name has changed to ???).
You have some good photos for reference to start with. Getting the dimensions correct would be aided by the building of the 3D model.

Then I would set about casting or machining the engine and gearbox and frame components etc.from the drawings you produce in the 3D software.

If you wanted exact scale then a few more photographs would be needed. You have several options there, you could plan a trip to a museum where one of these exists or you could write and request a detailed photo set, at cost of course, and/or scour the internet for more photos.

You could probably get away with using modern bicycle wheels with a few mods but overall it is quite doable.

If you wanted to use an existing engine, then multi-cylinder model aircraft engines are available up to 250cc, however, they can get quite expensive and they would not reflect the original style of the engine.

Good luck with your project, it is certainly a very nice example of a rare early motorcycle and I for one, would love to see this machine modeled at any scale.
 
Ill have to get some modeling soft ware on my laptop then start working on th frame design, i love the look of the inline 6 that member Draw-Tech is designing I could put that in there. Im also thinking of building a tom thumb mini bike and extending the frame to except the engine
 
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