PM Research #4 - Quarter Horse Vertical Steam Engine

[larry_g]

A couple of things that worked well for me on my engine.

On the eccentric strap the print has you drill through the threaded rod connection point and into the strap so that the hole in the strap becomes an oil hole.  I moved this oil hole around so that it is between the rod and the connecting bolt.  This allows easier oiling and access to the grub screw in the eccentric so one can adjust the timing without removing the eccentric strap. ( Thank you Keith Appleton)  Also with mod you can line up the grub screw hole with the oil port and fill it with oil, making it somewhat a reservoir.

On the valverod to the flex joint connection I deleted the pin and made this connection threaded. I extended the length of the coupling so that it had plenty of thread length. My thinking was that as designed you could only adjust the valve position by one thread pitch at the eccentric strap and I wanted something finer.  Once running I could adjust the valve position, while running, by turning the valve rod by hand and getting the best running that I could. 

These two changes made getting the valve timing and position very easy and for me it was a success.

lg
no neat sig line

My suggestion above I threaded the upper linkage part #23, not the valve.  That way the adjustment happens outside the block.  When running I can adjust the valve position while running and then the locknut is at the flex, not the valve.  Being the valve is round it is free to turn in the bore.

Did I say before that I wish I had your build to follow when I built mine.  Some of your setups and procedures are simpler than mine.

lg
no neat sig line

[propforward]

Aaaaaaaaah - that makes more sense Larry. Well I can still do that, and I shall. I’ll think on whether or not to keep the threaded valve for connecting to the rod, but going back to a pin might make more sense. Or try it threaded and change if needed.

Thanks for looking in - appreciate your insight and comments!

[larry_g]

I would think that having the valve threaded would be OK. Not a lot to loose if it doesn't work.  On a side note the engine will run just fine without the caps on either end of the bore.  The caps only ever see exhaust pressure and control the flow path.  The lower also provides support for the valve rod, but it will run with out it.  I had some fun with the exhaust pipe length.  The sound of the engine will vary a bunch depending on the pipe length and mine sounded best with a 1.5 to 2" long pipe.

lg
no neat sig line

[propforward]

Some days are better than others. I had hoped to have a selection of specially made studs to show off, but all I have for a days work is a bunch of scrap steel.

Ho hum. Try again. I thought these would be simple parts. Maybe I got complacent - pride cometh before a fall and all that.

No pics. Noooooooooooo way. Maybe have some by the end of the evening.

[larry_g]

I cheated, I used set screws of the proper size........

lg
no neat sig line

[propforward]

That's fair enough. I want to use close fitting studs to aid in maintaining alignment of the caps to the pillow blocks. Not really necessary, but an exercise in precision of sorts. Happily today was a lot more productive than yesterday and I now have my custom studs made. They are .001" clearance to the holes in the caps, and the caps slide over them when they are installed - it's a very close fit, they are not what I would call a "sliding" fit, more of a transition, but not a press fit. Since I drilled the holes in pillow blocks and caps separately, and did not transfer drill them, I am very happy about this - means that I must have the mill and lathe set up pretty well. This sort of precision was always my goal and I'm finally getting there. The recent fixes to the lathe have had a lot to do with this level of fit.

Anyway, I have been setting up the bearing blocks in the mill to clean up the bearing castings now that I have the studs made. This is all, as usual, taking a LOT longer than I planned. Doesn't matter though - no scrap parts made today, so much better than yesterday.

Pics of progress tomorrow.

[Dave Otto]

It takes time to get things the way you like, the devil is in the details. As far as I'm concerned it is perfectly ok to worry about things that no one will ever see.
Ask me how I know.

Dave

[propforward]

Very true Dave!

Well, a few pictures of a few things. Not doing a blow by blow account here, because most of this is straightforward. I did run afoul of the higher load generated from form tools, and tool heights set too high, and inappropriate machining sequence on slender parts, as well as too much stickout, the combination of which made me scrap too many of my precious studs. Still, that's all worked out and I'm chunking through them.

I want to make custom studs because I want to locate the crank bearings and engine frame more closely than a regular machine screw will allow. So I am making studs with a shaft closely sized to the holes in said items (I didn't think of it at the start of the build or I would have reamed the holes to a more round size, but no matter).

I ground a form tool to radius the showing end of the studs for appearances sake.





Fairly pleased with that - I ground the radius using a small round bit in a dremel, and using a radius gauge as a template.

Anyway it works out OK, the studs for the caps are a close fit, so now I can finish machining the bearings.



Which I am doing here using a vice in a vice. I decided to copy a previous build here, and just clean up the angled faces of the bearings. I think this will look good. Here I am touching off on the casting in 3 spots to get the surface level.



Then skim over it:



A little hand blending is needed now on the castings to fettle the caps to the pillow blocks, and I also need to make studs for the pillow blocks to the base. Work in progress in the foreground.



It took a silly amount of time to figure out the studs - but hey ho, they are now coming out how I want them. I haven't documented the process because for most people it's rudimentary stuff that we've all done. I think.

Anyway, I also made a packing nut, from a piece of hex bar.



I am a big fan of the upside down threading tool approach, running the lathe in reverse and threading away from the headstock. It is very stress free.

Touching off on a sharpie mark to establish the OD:



This is a 1/2-20 thread. I tend to cheat on my single point threads and just use a nut to check how they are coming along. Since I'm not selling these parts I'm OK with that, but today, since I have a set of thread wires, I just felt like trying them - and actually they are easy to use. These ones have a little rubber device which holds the pair of wires for one side, and attaches them to the micrometer anvil, making taking the measurement a very simple job.



The maths is actually pretty straightforward. I'm not going to go into that because there are many many many sources on the net and youtube that explain it, but there is a handy dandy chart that comes with the wires to make it easy.





A simple part really, very therapeutic. It even fits the mating part.



Anyway, that's a few things I have been doing. As usual, when I write about it I wonder what took so long. Nearly finished on the bearing studs, then I just need to make some custom nuts and I can machine the crank shaft bearings. Something a bit more interesting - after that I will be onto the crankshaft I think.

[Admiral_dk]

Nice progress Stuart and the parts looks good too     

Per

[Baltic]

Nice job with the thread & brass fitting Stuart.

You are spot on, single point thread cutting is very rewarding,

I have heard of the reverse threading method, but never tried it,
well I have only cut a couple of threads on the lathe anyhow 

Have you got a foot break on your lathe?
And, in your case did you spin the lathe in a forward direction to return to start? or simply using the thread dial?

Gary

[propforward]

Thank you both!

Gary, I do not have a footbrake on this lathe. That would be a nice feature but it's a fairly basic machine. This was a 1/2-20 thread, and I have an 8 TPI leadscrew so I can use the threading dial, and just return the carriage by hand. I like to put an undercut on the thread so that gives me a space to move the tool in and wait until the dial comes round - this makes for a nice thread. I have also learned to just run the lathe slowly for single point threading. Theoretically given that I'm cutting away from the headstock I can use a higher speed to better suit the diameter and material, but in reality I've learned it's easier for me to engage the half nut in the right spot by taking my time. I do occasionally get ahead of my abilities.

[Craig DeShong]

Nice work Stuart.

 

[Grateful Ted]

Although I frequently turn from the headstock out, I’ve never threaded that way.
I’ll have to try that.

[propforward]

Just make sure that your chuck cannot unscrew - mine is a threaded chuck mount, but it has screw on locks that prevent it unscrewing when turning the chuck in reverse.

I like it as a single point threading method because in general you just run off the part, giving you a lot more time to deal with stopping the machine, plus you are not trying to wind the cross slide out at the same time to stop cutting and so on.

[Grateful Ted]

Yes, had the chuck begin to unscrew many yrs ago on my SB9. Sol long ago that I can’t remember just what I was doing.
I do remember that it got VERY interesting in a hurry.
I suppose I could try reverse threading with my er32 collets, as I hold the collet chuck in the spindle with a drawbar.
I always use the back gears when threading @ about 50 RPM with no problems, so probably won’t’ try it.
I’ve always wondered how folks thread with lathes that have 130 or 150 RPM as the slowest speed.
I guess you adapt, I dunno.