Pipe and Bolt Engine Mod-Up

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SwarfnStuff:
A most interesting project / challenge and I have been following with interest since day one. The problems and solutions plus the ingenuity of converting what many would see as junk into working junk. :doh: :Doh: :update: Oops! Bad John. I mean, hopefully Working Engines is well worth the wait. Thank you so much for posting.
John B

RussellT:
Thanks everyone.

No one has made anything run yet Shipto. :poke:

OK, now it's time for a bit of theory.

The wobbler I am making has an unusual feature. I've never seen it before so please let me know if you have.

The unusual feature is that it uses the thread of the original bolt in the original nut to mount the cylinder, provide the bearing for the oscillation and to provide the sliding surfaces for the valve gear and a seal for the air/steam.

As the cylinder rocks back and forth, the bolt end rotates to and fro in the nut and with suitable holes drilled provides a valve action like this.

This is where my earlier calculation mistake became a problem as when I calculated it correctly I discovered that the ports were only 1.4mm in diameter (less than a 1/16") and I didn't fancy my chances of drilling those without a much larger supply of drill bits. Note that the area could be increased if necessary by drilling multiple holes.

After a bit of thinking I realised that the holes could be any size I wanted (within reason) as the dimension I'm concerned about is the overlap of the ports, not their diameter.

So here is a revised version showing 3mm diameter ports.

And here is a diagram showing how if I add an extra port and arrange the nut to rotate as well I can make the engine reverse.

Unfortunately this has the inner ports at an inconvenient and difficult to lay out 118 degrees. :doh:

So what diameter port do I need for a 120 degree angle? Back to the calculator. :smart:

These calculations show a degree of precision that won't be achievable in practice. The mating surface is not flat - I'm using the pitch diameter of the bolt for the calculations. My plan at the moment is to make the ports undersize and creep up on the right size.

I'm also wondering how much to separate the inlet and exhaust along the length of the nut/bolt. :scratch:

Russell

vtsteam:
That is very cool Russell! I'd call it a rocking valve oscilator with a screw bearing. :clap:

What I particularly like is your reversing method. :thumbup: I think the challenge is going to be maintaining steam (or air) tightness around the screw threads, but I bet you work that out -- and anyway as long as it runs, it's an engine! All around clever and interesting!! :thumbup: :thumbup: :beer:

vtsteam:
Shipto, don't stop now, man..... your flywheel is cool and you stuck with the challenge of pipe, which is hard to do. We all want to see it running on something!

If it puts this for-fun project in perspetive, I had a bad day on mine yesterday trying to make a piston. I went to town to buy a few small pipe caps to turn and replace the piston that was too loose after reaming the cylinder. But the new one turned hard -- I got a lot of chatter in the lathe. So I actually worked on the lathe -- tightening the split sleeve bearing, and taking the carriage apart to flatten the gib and bearing edge. It was probably good to do, since the lathe had sat in storage for many years, but I was anxious to turn the piston.

With everything back together, I was still getting a fair amount of chatter, even at slowest speed, and with a carefully sharpened tool. Probably the cast iron caps this time were harder than what I'd used before. The other problem was that my 3 jaw chuck is just not well suited to the lathe -- it's quite thick, and with a backing plate the work is just held too far from the lathe headstock bearing for a 3/4" spindle to play nice with hard materials. This became apparent when I brought the tailstock into play, and turned between centers. Chatter gone.

Thinking I could finish the piston, now, I got it down to a perfect close sliding fit. I turned off the end of the piston, and started putting in oil grooves, when, crunch -- I broke through the side. Not enough wall thickness!

The new pipe caps were cored out much deeper than the old, past the threads. Part ruined, trip to town and 4 hours of fiddling with the lathe and then turning what I thought would be a great part. Oh well!

vtsteam:
Of course that wasn't an end to it -- thinking that maybe this cap had been cored off center, I proceeded to turn another one, and exactly repeat the same crunch. So I guess they are quite consistent, and obviously, so am I to a foolish degree! :)

In fact, I actually have 4 spoiled pistons now:

From left to right:

The new style pipe cap (too hard too thin -- but I bought 4 just in case!)
Piston#1 too big, but bored too soon so I couldn't reduce it enough.
Piston #2 too narrow after reaming the cylinder a second time,
Piston #3 The right size but crunched,
Piston #4 Crunched because I didn't trust the first crunch!

And finally, a pipe plug, which might just have enough thickness to work.

To add to the fun we have very cold temps today, and a super storm headed our way for this afternoon and tomrrow. Two storms actually, predicted to converge. We're expecting 20" of snow in 24 hours. So time to make the piston may be limited! :whip:

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