Dual web Crankshaft construction

[Howard_S]

I am trying to make a single piston dual web crankshaft for a miniature steam engine. I first tried to make it with separate parts and press fit shafts into the web with spring pins to secure the shafts. I had trouble getting the center shafts to be aligned perpendicular to the web's.
So now I am thinking of making the 1/4 in shaft and web from the same steel round rod 1 1/2 in dia. and then just pin the two webs together with a 1/4 in shaft and contained with 1/16 in spring pins. It seems to me that this is easy to do on the lathe and I only have to make sure the two webs are parallel with a block of the correct size.
Does this make sense?

 

[tghsmith]

use one full length shaft, after assembling cut the center section out..

 

[Howard_S]

use one full length shaft, after assembling cut the center section out..

Certainly better than my original approach, but I am concerned that in the process of sawing that will compromise the close fit to the web, also the spring pin is only protecting in the x- plane and the shaft can potentially move in the y- plane during operation of the engine.

 

[tghsmith]

 

[francist]

What about making the short centre section of shaft along with the two web sections from one piece on the lathe, and then adding the two outboard shaft sections afterwards? You could drill and insert that shaft as one piece even to ensure alignment, and then section out the short bit between the webs as the last step?

-frank

Edit: haven't seen the video yet, but looks maybe like a similar method?

 

[T Bredehoft]

One of the steam engins I made had two side by side cylinders. I made four throws, each with crank and pin holes, slid all four on one shaft, rotated and spaced the throws/webs as needed, inserted the pins in the two sets of throws, silver soldered everything in place and cut out the crank where it needed removed.

Spring pins don't sound really rigid.

 

[Howard_S]

Frank
I would like to do it the way you suggested but I'm afraid it's beyond my skill level at this point in time. I think the video by Appleton looks like the best approach, and I will not use the spring pins but dowel pins instead along with lock tight. Thanks everyone, some very good suggestions

 

[Howard_S]

One of the steam engins I made had two side by side cylinders. I made four throws, each with crank and pin holes, slid all four on one shaft, rotated and spaced the throws/webs as needed, inserted the pins in the two sets of throws, silver soldered everything in place and cut out the crank where it needed removed.

Spring pins don't sound really rigid.

After thinking about this for a while I decided to bite the bullet and try to make the crankshaft out of one solid piece of 1.5 inch round steel stock. I found a good article "How to Machine Crankshafts" by Ronald Chernich. I was successful on the first try, not perfect but pretty good. I used ER16 and ER32 collets to hold the material which made for a solid setup. Here are some pic's.

 

[T Bredehoft]

Looks good.