Chris's Slew-Crowd Engines

[cnr6400]

    Is Rodney Turnmore, the shop elf piston rod specialist going to handle making the rods? 

Re steam powered Zamboni's - I never saw one, but you could spot one pretty easy if the snow bin was puffing out steam...

[Roger B]

Still enjoying in the background     

How much compression do you allow for the piston O rings? In static sealing up to 30% seems to be used.

[crueby]

Still enjoying in the background 

How much compression do you allow for the piston O rings? In static sealing up to 30% seems to be used.

I don't measure it like that, so can't give a percentage. I cut the slots a few thou wider than the ring and close to the depth needed, so it will slip in and have a little wobble side to side when uncompressed, and measure the OD of the ring in place and compare it to the ID of the bore. Then cut the slot deeper till the OD of the ring in place is two or three thou larger than the bore. That usually gives me a fit that will just slide back and forth without too much stiction. Its no where near the compression that a static pressure load would get, but it gives me a good seal with an oiled moving piston. So, the end result works for me but done by trial and error till a good fit, not very scientific!  I am using Viton rings, 1/16" cross section, 75A durometer.

[crueby]

The shop elves got the blanks for the piston rods cut to length this morning, and made me up a chart of lengths of end steps for each one. Then we started in turning the ends of the first pair of rods, for the Marion engine. The ends were drilled/tapped for a retaining screw, and the outer end turned down for a post to be a close fit into the piston. Hard to see the step in the picture once scaled down for the forum, but its there. The step and the screw will capture the piston in position and keep it aligned. On final assembly I'll add some loctite to that joint.

Then turned each one around in the chuck and drilled/tapped the crosshead end, and loctited in a screw that will go into the end of the crosshead.

The screw was then cut off, the burr from cutting filed off, and a nut run on to check the threads. I like doing threaded ends like this since it gives clean threads right up to the shoulder with no undercutting required like if it was cut with a die. Also it takes less force to tap for the screw than to thread the end of a post, reducing the likelyhood of the thin round part spinning in the chuck.

This angle shows a hex head screw run in to hold the piston end together.

So far two pistons done, six more to go...

[cnr6400]

 

[vtsteam]

A fine row of pistons and rods, Chris! 

[Sanjay F]

That's a neat way of making the threaded crosshead end of the rod 

[Roger B]

The shop elves got the blanks for the piston rods cut to length this morning, and made me up a chart of lengths of end steps for each one. Then we started in turning the ends of the first pair of rods, for the Marion engine. The ends were drilled/tapped for a retaining screw, and the outer end turned down for a post to be a close fit into the piston. Hard to see the step in the picture once scaled down for the forum, but its there. The step and the screw will capture the piston in position and keep it aligned. On final assembly I'll add some loctite to that joint.

Then turned each one around in the chuck and drilled/tapped the crosshead end, and loctited in a screw that will go into the end of the crosshead.

The screw was then cut off, the burr from cutting filed off, and a nut run on to check the threads. I like doing threaded ends like this since it gives clean threads right up to the shoulder with no undercutting required like if it was cut with a die. Also it takes less force to tap for the screw than to thread the end of a post, reducing the likelyhood of the thin round part spinning in the chuck.

This angle shows a hex head screw run in to hold the piston end together.

So far two pistons done, six more to go...

Thank you    Very traditional make it to fit 

[crueby]

Thanks guys!  Just finished the second pair of piston rods, for the Erie engine. Miss Bucyrus is up next...

[crueby]

This morning I got the rest of the flock of piston rods made:

So, up next will be the crossheads. The elves makred out the lengths needed on a piece of bearing bronze rod:

before taking it to their pet metal-eating goat, Bea Andsaaw (say the name fast, you'll get it  ) to cut it into shorter lengths. Each is long enough for two parts, so I can use one end to hold in the chuck/collet/vise while working on the other end.

[cnr6400]

  Is Bea related to the famous metal eating goats from Kiruna in Sweden?  Pistons, rods and crosshead blanks look great!

[crueby]

Is Bea related to the famous metal eating goats from Kiruna in Sweden?  Pistons, rods and crosshead blanks look great!

Is that where the famous Swedish steel comes from (the, um, 'other' end of the goats?)   

[crueby]

Started in shaping the crossheads. First up were the ones for the Marion engine. The first end of the bearing bronze bar was trued up at the end, drilled/tapped for the piston rod, then the OD taken down to be a sliding fit into the guide tube, and finished off with shaping in the end that will be towards the cylinder. Took several tools to do that end shaping.

The bearing bronze cuts like warm butter, even smoother than brass, but with finer chips. Nice stuff. The blank was then turned around and the same done on the other end for the second crosshead:

I'll leave the two parts together for now - that will let me hold the bar in a collet block on the mill to flatten both sides and drill the wrist pin hole. Once that is done on both ends, it will be cut apart and shaping on the crankshaft end of each can start. For now though, on to the same steps on the Thew crossheads. They are same OD, but with a different shape on the end and overall will be shorter.

[cnr6400]

 

[bent]

Lovely work, Chris.  I do like that idea for the threaded piston rods, and a good explanation for "why".