Holt Engine (maybe)

[f350ca]

Embarking on a new project. This could take a while.
Bought a set of plans for a model of a 1910 Holt tractor engine, they were the predecessor to Caterpillar.
Its hopefully going to be a 4 cylinder overhead valve engine.
A lot of small parts for my big fingers and machines. lol
1 inch bore and 1 5/8th stroke. It has wet sleeves and individual jugs on a two piece block.
The plans call for 32 DP gears, that size cutters don't seam to be available from our Chinese cousins and a set of domestic ones is pretty pricey. Saw an article where a chap made a none spiralled broach. The center cutter cuts the tooth and the adjacent ones top and form the next gear teeth over. Made a cutter and it seams to work.

   

The camshaft gear and a depthing tool I made

   

Today I started the front gear case. Some scrap aluminum from an aircraft plant, sure machines nice.

   

   

[Highpower]

Very cool Greg.

My question is - how did you cut the tooth profile in the reamer eg. what kind of tooling?

[f350ca]

Thanks Willie,
The cutter is simply a rack in circular form, then gash the teeth and back clearance in the mill.
I went with 14 1/2 degree pressure angle as thats acme thread and could use my acme threading fish to check the lathe cutter and align it. Tooth spacing on the cutter is the same as a rack gear would be, got the formula from the machinist hand book.
Took two tries, I made the first cutter with too wide a tip on the lathe tool. When cutting the gear I was toping the teeth before I could get the measurement over pins right to get the pitch dia I needed.
Used O1 then hardened but didn't both annealing it, seams to be lasting well.

   

[Highpower]

You are definitely smarter than the average bear there Yogi.

[f350ca]

Nah, even a blind squirrel sometimes finds a nut.

[f350ca]

Finished the front gear case. Sand blasted it to give it a cast look. 

   

   

[TomG]

Looks like an interesting Greg. Where did you get the plans?

Tom

[f350ca]

A chap by the name of George Britnell made them up. At one time you could get casting set but no longer, so he made the plans for a bar stock build. He's an incredible model builder, the models of car engines he's made are spectacular, down to building the transmission for the back.
https://www.homemodelenginemachinist.com...ngs.31371/

[f350ca]

After removing a LOT of material from two blocks of aluminum I found an engine block
   
   

[TomG]

It's amazing what can be found in those things!

Tom