Author Topic: High Pressure Steam Table Engine  (Read 25423 times)

Offline vtsteam

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Re: High Pressure Steam Table Engine
« Reply #225 on: January 29, 2023, 03:20:17 PM »
Following along also.  :ThumbsUp: :popcorn: :cheers:
Steve

Offline crueby

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Re: High Pressure Steam Table Engine
« Reply #226 on: January 29, 2023, 03:42:58 PM »
Hi Jo,
With it cut as drawn, that extra length of the slot gives the wedge more room to travel as bearings wear and are taken up, at least on the full size engines. A common 'feature' on the original engines.

Offline Jasonb

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Re: High Pressure Steam Table Engine
« Reply #227 on: January 29, 2023, 04:18:14 PM »
As Chris says the green line should not be doing anything you want the cotter to be contacting the end of the rod and right side of the slot in the strap and the wedge to be contacting the bearing. Having a gap between wedge and the left side of the strap allows for taking up any wear.

Online Charles Lamont

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Re: High Pressure Steam Table Engine
« Reply #228 on: January 29, 2023, 04:48:54 PM »
I still don't understand that drawing. So far as I can see, there is an open slot milled across the end of the rod to accommodate the gib and cotter. This seems to provide an unconstrained system with an unknown spatial relationship between the rod and the other bits. In other words, what is preventing the strap, bearing halves, gib and cotter all falling off the end of the rod?

I think it would work as probably intended if the gib and cotter were moved some distance to the right, so that their slot can pass as a rectangular hole through the end of the rod.
« Last Edit: January 29, 2023, 05:19:07 PM by Charles Lamont »

Offline crueby

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Re: High Pressure Steam Table Engine
« Reply #229 on: January 29, 2023, 05:06:59 PM »
I still don't understand that drawing. What is preventing the strap, bearing halves, gib and cotter all falling off the end of the rod?
The wedges through the end of the strap go through a slot in the rectangular section on the end of the rod, and the slot keeps things in alignment. The bearings overlap both sides of the strap and the rectangular section on the end of the rod to keep them from slipping out of the opening. Many times on a full size one there is a set screw from the side to keep the wedges located, or a screw along the long axis of the wedges to set tension and hold them in place. Have got better diagrams here someplace (looking)

Online Charles Lamont

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Re: High Pressure Steam Table Engine
« Reply #230 on: January 29, 2023, 05:14:09 PM »
It should be as you describe, but have another look at the drawing.

Offline crueby

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Re: High Pressure Steam Table Engine
« Reply #231 on: January 29, 2023, 05:18:09 PM »
It should be as you describe, but have another look at the drawing.
Tha line she points at is not a cut through the whole strap, its a reference to the slot in the strap for the wedges.

Offline Jasonb

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Re: High Pressure Steam Table Engine
« Reply #232 on: January 29, 2023, 05:19:13 PM »
The other drawing for the two longer rods shows it correcty

Offline crueby

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Re: High Pressure Steam Table Engine
« Reply #233 on: January 29, 2023, 05:20:20 PM »
Thats a good drawing!

Online Charles Lamont

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Re: High Pressure Steam Table Engine
« Reply #234 on: January 29, 2023, 05:23:49 PM »
Yup, that's more like it.

Online Jo

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Re: High Pressure Steam Table Engine
« Reply #235 on: January 29, 2023, 05:36:27 PM »
Shame the sketch as it says doesn't match the drawn parts.

The red rectangles show where the clearance needs to go for adjusting the bearings. It only needs to be less than 0.4mm to work.

The strap needs to be longer than drawn: 16mm so that it goes to the full length of the end of the side rods and fits into the bearing.

Jo
« Last Edit: January 29, 2023, 05:44:03 PM by Jo »
Enjoyment is more important than achievement.

Offline springcrocus

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Re: High Pressure Steam Table Engine
« Reply #236 on: January 29, 2023, 05:50:57 PM »
Hello Jo,
Just read through from page 1. Another one joining your flock.   :) :popcorn:

Regards, Steve
Member of a local model engineers society
www.stevesbritannia.co.uk

Offline Alyn Foundry

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Re: High Pressure Steam Table Engine
« Reply #237 on: January 29, 2023, 06:01:27 PM »
I’m finding this particular section quite interesting.

At some point I will have to make the connecting rod for the Brayton Ready-Motor. I have a full length of BDMS bar waiting to be cut. I also have the cast Brass bearing shells on stock along with gauge plate to make the cotters. I’m going with 1/8” so as to match the stock of Gib head keys that I already have.

Looking at the engraving the strap appears to be just a strip of Steel formed into an elongated “ U “ section. Being a lazy engineer I was thinking on the lines of a single hole whose diameter is large enough to pass the cotter heads through and then the Gib key backed against it. The thought of broaching through some 30 mm of Steel is daunting.

 :cheers:  Graham.

Offline Jasonb

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Re: High Pressure Steam Table Engine
« Reply #238 on: January 29, 2023, 06:17:37 PM »
Graham as our models are unlikely to see the sort of loads that full size do we can cheat a bit.

Firstly you can make both bearing halves round or both square as the engraving does not show if it is half & half shaped like Jo's



Secondly and this is the cunning bit you can mill into the end of the rod which means you just have to mill a little way in from each side and file the ends squuare rather than have a full depth rectangular slot.





I did the big Tidman that way, bent strap on that one too




Offline Alyn Foundry

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Re: High Pressure Steam Table Engine
« Reply #239 on: January 29, 2023, 06:37:09 PM »
Definitely a most “ cunning plan “ as dear old Baldrick would have said Jason ….  :ThumbsUp:

However the simple round hole will not be seen behind the Steel strap is there another reason against this idea apart from alignment issues?

 :cheers:  Graham.

 

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