A-1 Walking Beam Engine

[chiliviking]

I have received my plans for the walking beam engine from A-1 Machining and have been studying them for a couple days and am not sure what to think. It seems that some of the dimensions are generated by some CAD program rather than practical thinking. Just a couple examples the profile on the outside of the beam is described 14.783 degrees.(like 15 degrees would just be too much and 14.75 would'nt be enough). The radius for a notch on the cylinder head to clear the valve actuating rod is called out as .100 which means you would have to use a .200 endmill which is not availble from any common source. Why not dimension the radius of the notch at .093 so a 3/16 endmill could be used or .109 using a 7/32 .

I realize that these are not major issues that can't be overidden with a little common sense but it brings me to the conclusion that this is a project that you wouldn't trust any of the dimensions on the print without considerable study of how each part interacts with the other parts. All projects require this to some extent however I also have built projects that could be completed without any deviations from the prints. Also it seems there may be some parts missing from the assy. drawing ( which is provided in a 00 font size if there is such a thing. How you are expected to read something so small is beyond me.)

I would really appreciate input from others that have had an opportunity to look at these prints. It looks like a great project but may require some serious rework to sucessfully complete. I also have some questions about the selection of materials called out but I'm surely not very qualified in that respect.

 

[Philjoe5]

Hi CV,
Since I put you on to this guy I feel I should comment. I agree on the font size, it's way too small. Also the drawings are too finely drawn to be reproduced into working drawings to be taken into the shop where they will surely get oily and greasy. I'm going to talk to Scott at A-1 in Toledo at the Model show in mid-April about both issues. The other issues you brought up are ones I can ask Scott about also. I hadn't really dug into the construction details that closely at this point :-[. However, having seen several working models at the show last year, and given Scott's quick responses to my emails so far I'm confident the model is doable, though maybe not as straightforward as some. I cut my first piece of stock today. I'm starting with the cylinder since that's looks sufficiently complicated to test my limits so far. I'll keep everyone posted.

Cheers,
Phil

 

[Hilmar]

Hi Phil.
Did you think about metric dimension.
0.1 = 2.5 mm
Hilmar

 

[Philjoe5]

Good point Hilmar, a 2.5 mm end mill would work. But I don't think that was the designer's intent since all dimensions in the plans are Imperial. Looking at the plan for the cylinder head, however, leads me to believe there's a fairly wide tolerance in the notch there so either a 3/16 or 7/32 end mill would work. Admitedly I haven't built all that many different designs of engines, 3 to be exact. But all 3 had little inconsistencies ??? in their plans that needed some recalculations or adjustment in tolerances. I just deal with them as they come up. ;D

Cheers,
Phil