Weld crank-case from steel plate?

[Doug4d3s]

I am thinking of attempting to build a small V-twin engine for a motorized bicycle project. The engine would be a very-low-RPM design (cross-head) and wouldn't need to put out much power, <1 hp.

My problem at the moment is the crank-case: having a casting made or milling the whole thing out of a single block seems fairly uneconomical (though I will admit I have not priced this option yet...). Is it possible to braze it together entirely from flat pieces of sheet steel? The only welder I have is an acetylene torch.

I have done other fairly "closed" parts before and have seen how the torch heat will cause the metal to warp, but at the same time, I have seen pictures of other people's projects online that were even more complex and they seemed to get them to come out straight in the end.
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[Harold_V]

Without seeing a design, it would be hard to provide a valid answer, but what you propose is certainly not impossible.

I would expect, however, that in order to achieve success, it would be important to be able to machine critical features after assembly. To weld or braze almost anything and not experience shrinkage and distortion is a long shot.

Harold

[willy]

Most crank cases I have seen in your application were hexagonal. The ends would have collars with gussets to support the bearings. The hexagonal sides then afforded the angle for the cylinder mounts.

Good luck in your venture, perhaps you will post a pic or 2?

[SteveM]

I would expect, however, that in order to achieve success, it would be important to be able to machine critical features after assembly.

If you think of your welded up piece as a "casting", then you have an idea of what you need to do for machining.

Steve

[steamin10]

Many weldments in steel sheet, (plates are 2" and over), are springy enough to lose alingments with heat variations. After welding a red heat soak of about 1-1.5 hrs will remove all the stresses and give you a better platform to start with.

If this thing isnt too big, a hot wire and some foam would get a good place to start and pour it off in aluminum salvaged from engine heads. Not that hard to do. The material is suited to heating, is light weight, easy to machine, and certainly more detail and refinements can be added to the basic design.

Just my thoughts.

[Orrin]

A friend of mine from Down Under fabricates bar stock engines. AFAIK, he has never had any problems with his weldments. Here is the URL for his Web page:

http://www.oldengine.org/members/randmingold/

Reg is amazing. He is the most prolific model engine builder I've ever known.

Regards,

Orrin

[Bruce]

Hello, I'm interested in this topic. Many of the old motorcycle engines had cylindrical crankcases of cast aluminum. I've though about using a thick walled aluminum tube and milling round sides or "covers" which would have the motor mount tab "ears" on them, everything bolted together. Presently I'm looking for plans for a little single cylinder engine. Anybody have ideas? Thanks.

[alphawolf45]

Hello, I'm interested in this topic. Many of the old motorcycle engines had cylindrical crankcases of cast aluminum. I've though about using a thick walled aluminum tube and milling round sides or "covers" which would have the motor mount tab "ears" on them, everything bolted together. Presently I'm looking for plans for a little single cylinder engine. Anybody have ideas? Thanks.

There is a free book written in 1906. Has plan to build motor bicycle ..I been Tempted but I have too many projects going already.. "Motor Bicycle Building" By PAUL N HASLUCK

http://books.google.com/books?id=NHhFDq ... &q&f=false

[Bruce]

Alphawolf, thanks. I had heard about this book some time ago but forgot about it. I will check it out.

[Bruce]

That is a great book! I just downloaded it and it is facinating. The publisher apparently produced and sold castings for the engine. I wish that somebody out there was producing castings like the one in the book. Thanks again.

[alphawolf45]

That is a great book! I just downloaded it and it is facinating. The publisher apparently produced and sold castings for the engine. I wish that somebody out there was producing castings like the one in the book. Thanks again.

Glad you like that Bruce.. I saved the book cause I like that one too.....I am building a full scale 3hp gas inboard engine designed in 1900- will weigh excess of 300lbs when finished.....Were it not for that project I would jump on the bike project myself...

Probably not a bad build. Could mill the bike frame components from barstock...I am not great at pattern making but this bike engine is not terrible complex...It is exactly the era that interests me...I would definitely like to build one...I do some casting for 'bout every project that I do ...

[Bruce]

Alpa Wolf, There is a great article on turning a motorcycle cylinder from cast iron on the lathe in the May/June issue of Home Shop Machinist by Bob Rodgerson. Check it out.