Scaling up a mill engine by 1.5x

[Philjoe5]

This idea of scaling up the horizontal mill engine kept nagging at me. I thought that when I started the walking beam engine I’d forget about it. But as the famous blues singer John Lee Hooker said in one of his songs “It’s (music) in there (his head) and it’s got to come out”. So I decided after spending a week doing some of the finer work on the walking beam I’d take a break and start machining the 1.5 x scale horizontal mill engine. This engine will have a 1.500” bore x 1.875” stroke.

I think someone on this board said it. When you scale up by 1.5x, you are really scaling up by 1.5 x 1.5 x 1.5 = 3.38 (Sounds like a Marv to me)! So my 2.5 lb cylinder block becomes 8.5 lb!

Boring the crosshead guide was a challenge. It’s about 4.5” long and I don’t have a boring bar with that reach. So I drilled and bored from opposite ends. Even though I used the 4 jaw chuck, the meeting wasn’t as clean as I’d like. This is only a guide so a little extra clearance isn’t such an issue.


Here’s a photo of the new crosshead guide and cylinder block next to the original scale.

I’m thinking this is going to be a great adventure. I’m really pumped up about both engines. Both require different techniques, most of them new to me. This is what it’s all about!!!!

Cheers,
Phil