Mystery steam engine

[Jasonb]

What is the diameter of the narrow part of the pin?

I would be tempted to mill off the head and reduced diameter, drill and tap what remains and then screw in a shorter one, maybe even just a hole to loctite a new one into. But wait to see what Charles thinks.

 

[chris123]

What is the diameter of the narrow part of the pin?

I would be tempted to mill off the head and reduced diameter, drill and tap what remains and then screw in a shorter one, maybe even just a hole to loctite a new one into. But wait to see what Charles thinks.

Hi jason
5.486 mm

 

[GreenTwin]

I would machine off the existing bosses flush, then drill and tap holes using fine threads, and make a new boss that are not so tall.
Pressing in a new boss could distort the piece.
I am not a big fan of loctite, but if I threaded in a new piece, I would use it.
If you used a slight shoulder, you could get the height of the boss exact.

.

 

[chris123]

I would drill out the existing bosses completely, thread the holes using fine threads, and make a new boss that are not so tall.
Pressing in a new boss could distort the piece.
I am not a big fan of loctite, but if I threaded in a new piece, I would use it.
If you used a slight shoulder, you could get the height of the boss exact.

.

Yes thats right
The radial arm is over 3mm thick
Bud charles reckon its hardened
Well i could test that with a file actually
Chris

 

[GreenTwin]

I would be a bit surprised if it were hardened.
I have seen model folks harden some parts, but it is certainly not universal.
.

 

[chris123]

I just quickly checked
Its not hardened so it could be
Iets see what charles thinks
Chris

 

[Jasonb]

It is not unusual to harden expansion links, as they take a lot more work to make than a die block you harden the link so that should things wear then the simpler dieblock can be replaced

I am not suggesting completely removing the pin, just the head and first reduced diameter and never suggested pressing anything in.

In this situation Loctite will give a longer length of engagement. The inner boss that the eccentric rod fits to looks to be 6mm long so you could only really drill 4mm into that plus whatever the larger diameter's thickness is, say 6mm max. You won't be able to thread to the bottom of that and you also won't cut the male thread right to the head of the new pin so may only have 3to 4mm thred length. But a pin in a plain hole would give the full 6mm contact.

 

[chris123]

It is not unusual to harden expansion links, as they take a lot more work to make than a die block you harden the link so that should things wear then the simpler dieblock can be replaced

I am not suggesting completely removing the pin, just the head and first reduced diameter and never suggested pressing anything in.

In this situation Loctite will give a longer length of engagement. The inner boss that the eccentric rod fits to looks to be 6mm long so you could only really drill 4mm into that plus whatever the larger diameter's thickness is, say 6mm max. You won't be able to thread to the bottom of that and you also won't cut the male thread right to the head of the new pin so may only have 3to 4mm thred length. But a pin in a plain hole would give the full 6mm contact.

Thats the situation
How about instead of shorten
Cut wide part off thread and put wide screw
In?
Chris

 

[chris123]

Thats the situation
How about instead of shorten
Cut wide part off thread and put wide screw
In?
Chris

Well it wouldent be strong anymore
Maybe not so good
Chris

 

[GreenTwin]

I like JasonB's idea, assuming that would give you the required clearance.
.

 

[chris123]

Yes

 

[Charles Lamont]

With Jason's scheme it be will difficult to ensure the two diameters are concentic. I would cut the head off, shorten the outer bearing diameter, and tap a hole in the end, making a new large headed screw and Loctiting it in, which I think is what you said, Chris. In fact the new piece could probably just be Loctited in without a thread, but belt and braces is probably better, if more work. I should think you will need 1/32"- 1mm clearance between the pins of the two sets of gear as assembled. What would that leave the lengths of the two bearing surfaces of the pin?

 

[Charles Lamont]

A question to help with thinking about the flywheel, What is the engine's stroke?

 

[chris123]

With Jason's scheme it be will difficult to ensure the two diameters are concentic. I would cut the head off, shorten the outer bearing diameter, and tap a hole in the end, making a new large headed screw and Loctiting it in, which I think is what you said, Chris. In fact the new piece could probably just be Loctited in without a thread, but belt and braces is probably better, if more work. I should think you will need 1/32"- 1mm clearance between the pins of the two sets of gear as assembled. What would that leave the lengths of the two bearing surfaces of the pin?

View attachment 164374

 

[chris123]

Hi charles yes thats what i meant
Bud it takes the strenght out of it
I check whats left
Chris

 

[Charles Lamont]

Drilling the pin half of its diameter reduces the bending strength of the pin by very little. By 1/16 I think, without getting my textbooks out to check.

In bending, which is what matters here, the middle bit does not do much, which is why lots of structures are made of quite thin wall tube rather than solid.

 

[chris123]

Hi charles yes thats what i meant
Bud it takes the strenght out of it
I check whats left
Chris

Quick question
Do the radius arms slide in the middle peace
Where the rods getting screwed in?

 

[Charles Lamont]

Here are a couple of drawings for you. Hot off the press so probably containing errors. These should fit in the valve cavity.
I need to double check, but not now as it is midnight here.

I have designed the lap and lead of the valve to suit the timing provided by the valve gear. The valve is slightly asymmetric to suit the ports.

A hex socket grub screw, with a copper pad under it to protect the valve stem should be sufficiently accessible inside the valve chest, though you might need a shortened alley key, or even two, one being twisted 30°.

 

[Charles Lamont]

Yes - that is how the engine is reversed, bringing one or other eccentric into play to work the valve while the other one flaps about doing nothing much.
It is more complicated than that, but that will do for now. The middle piece is called a die block, and the curved bar is an expansion link.

 

[chris123]

Here are a couple of drawings for you. Hot off the press so probably containing errors. These should fit in the valve cavity.
I need to double check, but not now as it is midnight here.

I have designed the lap and lead of the valve to suit the timing provided by the valve gear. The valve is slightly asymmetric to suit the ports.

A hex socket grub screw, with a copper pad under it to protect the valve stem should be sufficiently accessible inside the valve chest, though you might need a shortened alley key, or even two, one being twisted 30°.

View attachment 164382
View attachment 164381

Thank you heeeeeeeps charles
I checked the clearance on the brass block
And the spacers between the radial arms
They have to slide
Are too tight bud
Lap it??
Chris