Author Topic: Textile Mill Diorama  (Read 66468 times)

Offline wagnmkr

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Re: Textile Mill Diorama
« Reply #450 on: July 12, 2018, 11:36:15 PM »
Very slick John ... good looking parts.

Cheers

Tom
I was cut out to be rich ... but ... I was sown up all wrong!

Offline J.L.

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Re: Textile Mill Diorama
« Reply #451 on: July 13, 2018, 01:29:53 PM »
Thanks Tom,,

The engine will be asking you for a visit soon...

Now the measurement on a piece of paper become academic. It's time to let the engine tell me where things are at.

This first test is to determine the elevations of the parts. As I figured, the crossslide is too high.

The pointer in the first photo is centered on the axis of the crankshaft. This seems to be the point from which all other elevation heights will be taken.

In the second photo, you will see that the pointer is below the axis of the cross pin.

I have to shave off some material from the bottom of the crosshead.

I've also noticted in this first trial setup that the cylinder shaft is going to be too long. The measusrement on the drawings for the crank length should have been shorter.

That's what makes this game interesting.  :)


Offline J.L.

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Re: Textile Mill Diorama
« Reply #452 on: July 13, 2018, 10:26:55 PM »
The split block simply would not stop binding when  the bolts were drawn up tightly.
 
I can see why there are a lot of brass shims lying about in the machine shop.


Offline wagnmkr

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Re: Textile Mill Diorama
« Reply #453 on: July 14, 2018, 01:22:34 AM »
Thanks Tom,,

The engine will be asking you for a visit soon..


Yup, I am hoping very soon John.

Cheers

Tom
I was cut out to be rich ... but ... I was sown up all wrong!

Offline zeeprogrammer

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Re: Textile Mill Diorama
« Reply #454 on: July 14, 2018, 01:28:28 AM »
The split block simply would not stop binding when  the bolts were drawn up tightly.

I'd like to know more about that.

What exactly was binding?
I can't tell from the pictures...where was the shim put?

In any case...problem identified and problem solved.  :ThumbsUp:
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Offline john mills

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Re: Textile Mill Diorama
« Reply #455 on: July 14, 2018, 04:36:54 AM »
The hight of the crank shaft to the cross head is not as important as the piston rod  centre of the cylinder must be in line and same hight as the cross head  so when assembled it will slide full length of stroke if the crank shaft is at a slightly different hight it won't effect the running of the engine.
great to see the engine progressing.

Online Jasonb

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Re: Textile Mill Diorama
« Reply #456 on: July 14, 2018, 07:58:20 AM »
As John says set the cross head to the cylinder ctr line and unless the cross head to crank is massively out don't worry too much about it. I have done some engines where the crank is purposely offset to the cylinder.

Also check that your binding is not due to the edges of the bearing hole fouling a bit of loctite in the corners of the crank, you get similar problems with solid cranks where any radius on the tool leaves a filler to a could CSK of the bearing edges is needed. I usually blue the bearing, assemble and then when you take it apart you can see where the colour has come off and that is where it touches. Also if you have some of the same barstock as the crankpin try that in the hole without shims to see if it is OK, if it is then part of the assembly is causing the problem not the size of the hole.

Offline J.L.

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Re: Textile Mill Diorama
« Reply #457 on: July 14, 2018, 12:46:14 PM »
Thanks John.

Hi Carl and Jason,

Perhaps I used the wrong word and misled you when describing the fit of the split gunmental block on the crank pin. I should have used the word clamp instead of bind. When the bolts were drawn up snuggly, the block locked up as if gripped in a vice.

I was very careful to polish the pin and ream the block to exactly the same diameter - 7/16". Jason,I think bluing the bearing would work if there was rotation but binding. As you say, it would wear off the bluing and reveal a high spot.

No, I'm talking clamping the block solidly to the pin  After introducing a 0.00585 shim, I could feel a pleasing, firm, rotating pressusre when I drew up the bolts.

I am not worried about the location of the cylinder at all at this point. More about that later.

What I am working on now is getting the con rod and the crosshead running true to the central axis of the bed and locationg the sliding bars.

Thanks for the input.

John


« Last Edit: July 14, 2018, 01:36:29 PM by J.L. »

Offline b.lindsey

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Re: Textile Mill Diorama
« Reply #458 on: July 14, 2018, 01:27:31 PM »
I have been out of town for a few days so it is nice to see your progress John. Always makes me wonder if they had to do similar things when rigging full size engines back in the 1800's and early 1900's. I suspect they did, just on a whole different scale. Your work is progressing wonderfully and as always a joy to see your updates.

Bill

Offline J.L.

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Re: Textile Mill Diorama
« Reply #459 on: July 14, 2018, 01:54:28 PM »
Hi Bill,
I'm sure you are right. Filers and fitters must have had steady work not only with the initial fitting of parts for smooth running, but compensating for wear and tear as the engines aged.

Thanks for the poitive comments.

The notes that accompanied this kit, suggested that all parts in the power train be temporarily aligned and clamped in place before the slide bar holes were drilled.  Good advice. When I set everything up except the cylinder, I was sure things were 'in line'. Boy, was I wrong. The setup you see  before these pictures were taken was bearing at least 4 degrees to the left when viewed from behind. That meant the crankshaft bearing blocks had to be loosened and relocated to bring the crosshead around to the centre of its pad.

Thanks goodness Loctite was not on my mind earlier.

With the crosshead equally centered on its pad, the slide bars can be fitted.

You will notice a piston rod sticking out of the crosshead boss like a gun barrel. It is an extra rod I had made earlier and helped aim the parts. Gun barrel may be an apt analogy, for the whole system so far has been 'sighted in.'

About that Loctite, since I have enlarged holes for adjustment, it will definitely be needed to hold parts in place once the slide bars are bolted down.


From the sound of the above, you'd almost think I knew what I was doing! It's all a learning experience and total enjoyment from some daunting health issues. The kind advice and help on this thread is really appreciated.

Cheers...John
« Last Edit: July 14, 2018, 01:58:02 PM by J.L. »

Offline derekwarner

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Re: Textile Mill Diorama
« Reply #460 on: July 14, 2018, 02:10:25 PM »
JL.....with the ~~0.006" shims [plural] in place, rotate the crank so that the piston is in full extremity of stroke entry into the cylinder, ie., the  cylinder rod is in the 'true' horizontal plane

Place your dial indicator on the outboard or bottom bearing half...

Can you rock the cylinder rod to perceive & establish any movement?

If the bearing is a size for size 'clearance' on the pin and is free to rotate or float in that small clearance between the crankshaft web plates without the connection to the piston rod, however tightens up when the bearing halves ate tightened, then angularity of the crank pin is an obvious root cause of concern

Remember 0.0005" angularity on a 0.4375" diameter pin will be difficult to establish over a similar pin width

A method of checking for such alignment is to use a deformable Teflon cord of say 0.005" diameter....."yes just a little thicker than a human hair"

Place a length in the bottom 1/2 of the bearing shell [this will be sitting at ~~ the 3:00 o'clock position and tighten the bearing shell halves

The removal & measurement across the length [width] of engagement or the Teflon cord thickness will confirm the geometry

Derek   
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Offline Ramon

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Re: Textile Mill Diorama
« Reply #461 on: July 14, 2018, 03:43:15 PM »
......I was very careful to polish the pin and ream the block to exactly the same diameter - 7/16". Jason,I think bluing the bearing would work if there was rotation but binding.

Hello John,
Not withstanding all the sound advice you've had so far, but with regard to the above you have in fact produced a 'push fit' situation i.e. a size for size pin and hole is a tight push fit under normal circumstances.

Usually the crankpin diameter is made size and the bearing eased to suit. In full size circumstances these parts would be made in the 'machine shop' and the 'fitting' carried out by 'fitters' in the erection shop. Fitting a shim should be a last resort and usually only then to make up for 'lost' material. As you still have material to remove that's what should be tackled to ease the fit to the pin. A combination of scraping the halves and/or easing with wet and dry paper wrapped tightly around a dowel will soon see to it. I have several half round needle files with the very tips ground to act as scrapers for just this sort of situation. Might be worth investigating?

Re the cross head I would concur with Jason and John Mills in that the first matter is to ensure the cross head centre-line is made relative to the centre-line of the cylinder in both planes and ensure free movement of the cross head in the bars or slide for the length of stroke with the piston and rod fitted before dealing with the Con-Rod hook up. Freedom of movement here will allow you to spot quickly any slight tightness when you do then fit the Con Rod.

I have all this to come on my build but the above is based on previous engines - hope that adds to the melting pot some. It's all looking very good despite your odd fitting problem :ThumbsUp:

Regards - Tug
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Offline J.L.

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Re: Textile Mill Diorama
« Reply #462 on: July 14, 2018, 04:10:48 PM »
Thanks again for all the help and suggestions fellows.

Derek, that was right over the top of my head. You realisze you are talking to a woodworker who has graduated from the use of a tape measure...

I must be beating a different drum here. I want everything dead on before I begin to machine off material from the bottom of the cylinder which I know is too high right now. Then there will be no guesswork as to determining the common horizontal axis of the crosshead bore and the cylinder rod.

With that in mind, here is the set-up to determine the location of the slide bars.

Offline Ramon

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Re: Textile Mill Diorama
« Reply #463 on: July 14, 2018, 06:07:15 PM »
Ah, I see John - I was assuming you had the cylinder machined with the centre line of the bore determined.  You're on the right route then, just a different track  :D Have you thought how you will go about machining the cylinder to get it spot on height?

If it helps....

When I set my Corliss up in the first instance one cylinder required a small amount off the bottom - much the same situation as you will have I guess. In order to ensure the base was parallel to the bore I set it up on a close fitting bar passed through the bore supported on two vee blocks. There's a pic of the first set up to bring the base to dimension using a smaller than the bore diameter bar to do this here http://www.modelenginemaker.com/index.php/topic,7688.15.html - you'll need to scroll down to post 28 if it's of help.

When I finally bolted the cylinders on though there was a very small discrepancy so it was set up exactly the the same but as said this time with a much closer fitting bar through the bore to ensure the base was as parallel to the bore as possible. Worked out very well.

Regards - Tug

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(a very apt phrase - thanks to a well meaning MEM friend)

Online Jasonb

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Re: Textile Mill Diorama
« Reply #464 on: July 14, 2018, 06:30:11 PM »
John, I was rather hoping that the almost 6thou shim was a typo and that you had used a 6ths one. It is worth considering what you have actually done to the shape of the hole.

Looking at this sketch by inserting the shim you have gained a slight clearance top and bottom on the split line as highlighted which has been enough to cure the tightness. But at the widest points indicated by the blue arrows you have got the best part of 3 thou gap which is rather a lot.

As most of the engines force will be at these mid points you will soon develope a nasty knock as the tiny contact areas top and bottom bed in.

I feel you would be better off removing the shims and just easing the hole slightly. Generally over here a nominal 7/16" reamer will be made to give an H& tollerence hole which is a few tenths over 0.4375" and will give a running fit. If you don't have a reamer like this then the two methods Ramon mentioned will do, I have a miniature triangular scraper which is ideal for removing small amounts of metal on bearings.

When I mentioned blueing the parts the method is to blue then, a marker pen or sharpie will do and then do up the nuts until you just start to feel things starting to tighten and then revolve the bearing on the pin, take apart and look to see what is touching and remove metal as needed. You may have to repeat this 10 or more times be it is worth it in the end for a properly "fitted" bearing.

As Ramon said shim was not often used to open up bearings. It was either placed behind a worn bearing to close up the wear or several shims placed in the joint and then the hole machined, any subsequent wear could then be taken up by removing shims, you often see this with babbit bearings.

As for adjusting the height of the cylinder I would suggest you remove metal from the bed casting as it will be easier to leave the engine on the mill table and take off test, then take off metal and test rather than having to set the cylinder up several times to skim the bottom with the risk of the base not remaining parallel to the bore.