crank size diameter
- Thread starter itowbig
- Start date
Help Support Home Model Engine Machinist Forum:
;D ha ha stan ya thats kind what im thinking too ;D i have a .879 piston and tha material that i have to make a crank out of is flat bar=.375 so the diameter would just a tad smaller than that. i think it will work but not sure till i get it made. 
PolskiFran
Well-Known Member
- Joined
- Dec 7, 2007
- Messages
- 61
- Reaction score
- 0
My Upshur Vertical gas engine has a 3/4" dia piston, 3/16" wrist pin, and a crankshaft made from 1/2" thk. hot rolled steel with 5/16 dia. journals for both the connecting rod and main bearings. It has been working well for years.
Hope this helps,
Frank
Hope this helps,
Frank
On a more serious note than my previous post:
The two requirements in models are appearance and reliability.
In model engines, crankshaft loading is pretty much a non issue, unless you are doing high compression diesels. The majority of models do no work other than overcome friction to keep running. If the crankshaft is big enough to support the weight of the flywheel, the chances of the flywheel flying into space (with a broken shaft) is slim.
Looking at the pictures of engines on this board, have you ever wondered if the crankshaft was sized correctly, or even made out of the proper material. Good looking models are just that. The overall design and quality of workmanship is paramount. I expect there are perfectionists who make every part to the precise measurement on the plan, but it is much easier for most of us to make the difficult parts first and make the easily machined parts to fit. This usually means making holes first and things that must fit the holes last (cylinders first and then pistons, bearings first and then shafts).
Making a sketch to scale gives a pretty good idea of what size will look good in the finished model.
The two requirements in models are appearance and reliability.
In model engines, crankshaft loading is pretty much a non issue, unless you are doing high compression diesels. The majority of models do no work other than overcome friction to keep running. If the crankshaft is big enough to support the weight of the flywheel, the chances of the flywheel flying into space (with a broken shaft) is slim.
Looking at the pictures of engines on this board, have you ever wondered if the crankshaft was sized correctly, or even made out of the proper material. Good looking models are just that. The overall design and quality of workmanship is paramount. I expect there are perfectionists who make every part to the precise measurement on the plan, but it is much easier for most of us to make the difficult parts first and make the easily machined parts to fit. This usually means making holes first and things that must fit the holes last (cylinders first and then pistons, bearings first and then shafts).
Making a sketch to scale gives a pretty good idea of what size will look good in the finished model.
Similar threads
