Author Topic: PMR 7 Twin Cylinder Steam Engine  (Read 32054 times)

Offline crueby

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Re: PMR 7 Twin Cylinder Steam Engine
« Reply #270 on: May 03, 2018, 12:01:11 AM »
Hi Carl I'd like to see your engine running but it says the video is unavailable ?

Have you set it to private view only ?  :(

I did. I didn't see Chris' post until after. Odd though. I logged out and could still see it. (Odd or suspicious?).

I'll try again.
If its private, only you can see it. Privately.

Offline zeeprogrammer

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Re: PMR 7 Twin Cylinder Steam Engine
« Reply #271 on: May 03, 2018, 12:03:12 AM »
Hi Carl I'd like to see your engine running but it says the video is unavailable ?

Have you set it to private view only ?  :(

I did. I didn't see Chris' post until after. Odd though. I logged out and could still see it. (Odd or suspicious?).

I'll try again.
If its private, only you can see it. Privately.

Yeah but what bothers me...I logged off. How do they know. No matter.

See if it works now. I changed the settings to unlisted.
If that doesn't work I'll try posting again.
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
"To work. To work."
Zee-Another Thread Trasher.

Offline crueby

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Re: PMR 7 Twin Cylinder Steam Engine
« Reply #272 on: May 03, 2018, 12:04:40 AM »
Hi Carl I'd like to see your engine running but it says the video is unavailable ?

Have you set it to private view only ?  :(

I did. I didn't see Chris' post until after. Odd though. I logged out and could still see it. (Odd or suspicious?).

I'll try again.
If its private, only you can see it. Privately.

Yeah but what bothers me...I logged off. How do they know. No matter.

See if it works now. I changed the settings to unlisted.
If that doesn't work I'll try posting again.
You are logged off, but still have my favorite topic - Cookies!

Working fine now!

Offline b.lindsey

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Re: PMR 7 Twin Cylinder Steam Engine
« Reply #273 on: May 03, 2018, 12:17:07 AM »
They recognize your ISP Zee even after you log off so they know its still you ...scary huh??  That one side is running great. Now just get the other to match and you're all set. Looks great though!!

Bill

Offline zeeprogrammer

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Re: PMR 7 Twin Cylinder Steam Engine
« Reply #274 on: May 03, 2018, 12:29:43 AM »
Thanks Bill.

And thanks Chris for letting me know about the settings.
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
"To work. To work."
Zee-Another Thread Trasher.

Offline b.lindsey

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Re: PMR 7 Twin Cylinder Steam Engine
« Reply #275 on: May 03, 2018, 01:27:05 AM »
Zee, when  you say the slides may be too high....what are we talking about here, .001" (which could still cause some binding) or something more...like .005" or more? If you lower the slides too much the hole the piston rod fits into may become out of line then. Just thinking out loud. Fixing one issue may cause another.

Bill

Offline zeeprogrammer

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Re: PMR 7 Twin Cylinder Steam Engine
« Reply #276 on: May 03, 2018, 01:33:02 AM »
Zee, when  you say the slides may be too high....what are we talking about here, .001" (which could still cause some binding) or something more...like .005" or more? If you lower the slides too much the hole the piston rod fits into may become out of line then. Just thinking out loud. Fixing one issue may cause another.

Quite so Bill. I'm taking it very slow. It keeps getting better but at some point I may turn a corner and find I've screwed something else up.
The cross head itself can be easily remade.
Redoing any parts of the cylinder is more problematic as they are cast. Although I could probably get away with redoing the head cover as it doesn't show much.

I noticed that if I tighten the bottom bolt and slightly loosen the top bolts (of the cylinder), it runs better. But that may be a symptom of the same thing.
I would be surprised if things are canted. Everything was done at the same time.

I'll see if I can figure out how to measure things a bit better. It could be the slides have to drop but I'm not ooking forward to that.
Putting a part (in this case, the base) back in it's original setup has nearly always met with disaster for me.

Still optimistic.  :ThumbsUp:

[EDIT] Just to be clear...it's the cross head I'm modifying. Not the slides.
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
"To work. To work."
Zee-Another Thread Trasher.

Offline b.lindsey

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Re: PMR 7 Twin Cylinder Steam Engine
« Reply #277 on: May 03, 2018, 01:38:33 AM »
It seems the crosshead would be the easiest part to remake. I kind of doubt the cant theory too given how you machined things. If you shave off a small amount from the underside of the crosshead, it would do the same thing as lowering the slide a bit. If that frees things up then great. If t results in the crosshead being a bit loose in the slides you can reduce the height of the spacers to tighten things back up. That seems the easiest and safest route to me unless you find something else obviously out of whack :)

Bill

Offline zeeprogrammer

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Re: PMR 7 Twin Cylinder Steam Engine
« Reply #278 on: May 03, 2018, 01:44:47 AM »
It seems the crosshead would be the easiest part to remake. I kind of doubt the cant theory too given how you machined things. If you shave off a small amount from the underside of the crosshead, it would do the same thing as lowering the slide a bit. If that frees things up then great. If t results in the crosshead being a bit loose in the slides you can reduce the height of the spacers to tighten things back up. That seems the easiest and safest route to me unless you find something else obviously out of whack :)

That's exactly the road I'm travelling. I'm very glad it's not an unusual road. Thanks Bill.
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
"To work. To work."
Zee-Another Thread Trasher.

Online Kim

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Re: PMR 7 Twin Cylinder Steam Engine
« Reply #279 on: May 03, 2018, 07:08:55 AM »
Hi Carl I'd like to see your engine running but it says the video is unavailable ?

Have you set it to private view only ?  :(

I did. I didn't see Chris' post until after. Odd though. I logged out and could still see it. (Odd or suspicious?).

I'll try again.
If its private, only you can see it. Privately.

Yeah but what bothers me...I logged off. How do they know. No matter.

See if it works now. I changed the settings to unlisted.
If that doesn't work I'll try posting again.
You are logged off, but still have my favorite topic - Cookies!

Working fine now!

Actually, I think that you saw it because it was cashed by your browser.  Even though you'd logged off, unless you clear your browser cache, it will show up.

You're engine is looking great, Zee!
Kim

Offline Steamer5

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Re: PMR 7 Twin Cylinder Steam Engine
« Reply #280 on: May 03, 2018, 07:47:34 AM »
Hi Zee,
 Keep at you will win!

Before you launch into major head scratching on setups, have you tried flipping the crosshead over? Or as the other cylinder works how about using the cross head from that cylinder? MAKE SURE YOU MARK IT THE RIGHT WAY UP FIRST! Try the suspect one in the running cylinder.
Now if you have tried this.......blame the elves!

Great work, looking forward to seeing it running!

Cheers Kerrin
Get excited and make something!

Offline zeeprogrammer

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Re: PMR 7 Twin Cylinder Steam Engine
« Reply #281 on: May 03, 2018, 11:56:12 AM »
Thanks Kim.
Thanks Kerrin.

have you tried flipping the crosshead over? Or as the other cylinder works how about using the cross head from that cylinder? MAKE SURE YOU MARK IT THE RIGHT WAY UP FIRST! Try the suspect one in the running cylinder.

That forces me to come clean (although I think I'd mentioned this earlier)...

Unfortunately, the cylinders are not perfectly placed between the two slides. That is, the piston rod going into the cross head is slightly off center.
In addition, the gap between slides differs slightly from one set to the other.

In short, the cross heads can only go one way and are custom to their slides (cylinders).
The differences are slight but significant enough.

As people said, and as I knew...I'd learn a lot on this.

Amongst other things, the biggest take away is to measure, measure, measure. The difference in spacing for the slides should have easily been caught if I'd double-checked more while milling.

Another big take away (and one I keep ignoring) is when I hear myself think "that seems odd"...investigate!
Regarding the slides again, it bothered me that the distance between slides was .75" and the raw material was .75" wide. It seemed odd that I wouldn't have to mill the sides of the cross head. I had gone by what I'd seen a website to cut them but had I rotated the part 90 degrees I would have gotten the same two parts but would have milled all 4 sides instead of just two.  Having said that though, the cross head was spec'd to be .187" and the raw material was 3/16". So the faces would simply get a lick of sandpaper.

Two other areas I'm working on improving include accounting for backlash and locking gibs down.
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
"To work. To work."
Zee-Another Thread Trasher.

Offline AOG

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Re: PMR 7 Twin Cylinder Steam Engine
« Reply #282 on: May 03, 2018, 12:38:56 PM »
The quickest way to find out if the crosshead is tall or the cylinder is cocked is to pull off the slides and crosshead. Measure the height of the piston rod relative to the slide base at both ends of the travel. If it’s the same height at both ends trim the crosshead. If not you will have to shim the cylinder.  That assumes that the cylinder cover is evenly torqued. There is enough squish in the gasket material for uneven torque on the cover to throw off the alignment at the end of travel. I think part of it down to the uneven spacing of the three holes. Just by the nature of the design, there is more force applied at the top of the cylinder head than on the bottom.

My 2 cents

Tony

Online sco

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Re: PMR 7 Twin Cylinder Steam Engine
« Reply #283 on: May 03, 2018, 12:40:59 PM »
Zee,

Not convinced on the need for a DRO on the lathe but on the mill they absolutely transform the ease of machining parts - no more mental arithmetic or worry about backlash - I couldn't go back to a mill without one fitted now.

Simon.
Ars longa, vita brevis.

Offline Jo

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Re: PMR 7 Twin Cylinder Steam Engine
« Reply #284 on: May 03, 2018, 01:13:03 PM »
Not convinced on the need for a DRO on the lathe but on the mill they absolutely transform the ease of machining parts - no more mental arithmetic or worry about backlash - I couldn't go back to a mill without one fitted now.

There are much higher priorities for the workshop than a DRO on the lathe.... but when you are struggling to find another goodie to buy for your favourite workshop they are rather nice  :embarassed:

Jo
Enjoyment is more important than achievement.

 

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