1/8 Rider Ericsson - Home build

[creast]

Thanks Pat
The finish needs improving but as most of the engine is paint finish I can get a bit of Bondo out .
Will be having a break for a few days and then back to some fiddly bits.
Rich

 

[creast]

I have had a break from the workshop but will now crack on with the project.
I am hoping that someone here may be able to answer my question regarding the displacer cylinder materials specified in the build manual.
The cylinder is specified copper with a steel flange silver soldered in place and the end cap/ diaphragm is thin stainless steel.
I have previously built a Ky-Ko fan which had an all stainless displacer cylinder and runs very well and an insulating gasket reduces heat loss to the framework.
In the build log it mentions reducing the wall thickness of the copper to reduce heat losses to the mounting flange.
So why use copper in the first place and why not copper instead of stainless for the end cap where the heat is to be taken in???

 

[creast]

Had a chance to try another casting today but took me three goes to get a reasonable result.
The yoke casting was an awkward one and so I decided to use a core to help and odd sided the mould.
Yet again plenty of flash as the mould didn't separate clean but in the end I got a casting.

 

[creast]

Another week has passed and has been mainly machining parts that were cast earlier or from stock material.
Today I cast some home made tin bronze for the walking beam bearings and decided to re-do the support in the same material as it was there and needed re-casting from the last failure.
I was surprised that the lost PLA casting actually came out great as the melt seemed very sticky and I did not pre-heat the mould.
There are a few questions I have regarding home brew alloys but I will post them in the foundry section.
I have to wait for some material to be delivered for the power piston and cylinder flange.

 

[creast]

I have been busy machining pivots, shoulder pivot screws and also probably cast the final casting of the project which is a mounting frame/rim to hold the firebox.
This will be silver soldered to the firebox and suspended below the baseplate so Brass was order of the day.
Quite a fine casting which was made in Petrobond sand, its only 2mm section by 2.5mm depth.
First cast failed to fill so an extended sprue was used on the 2nd attempt and success!
The cross feeders help the fill and also support the rim for subsequent machining before being removed.

I now have to tackle the power piston.

 

[GreenTwin]

I use knife gates quite a bit, and find them effective at spreading out the metal flow, lowering the metal velocity, and helping to completely fill thin sections.

I typically use multiple gates on a part too, to fill from both sides.

That is a nice frame, and so tricky to cast.
Hats off to you sir !!!

.

 

[creast]

I use knife gates quite a bit, and find them effective at spreading out the metal flow, lowering the metal velocity, and helping to completely fill thin sections.

I typically use multiple gates on a part too, to fill from both sides.

That is a nice frame, and so tricky to cast.
Hats off to you sir !!!

.

Thanks Pat.
First attempt failed to flow more than 10mm from the gates so I extended the sprue height and made sure the brass was well hot.
Even at this scale there was very slight contraction dimpling at the lugs but it cleaned up ok

 

[GreenTwin]

Every part seems to mold up and cast a little differently.
I always lament that if I only had known last year what I know today, I could have done it differently/better.

I watch every casting thread and video I can find, because better to learn others mistakes and successes, and perhaps save myself some time.

I am quite sure I will never learn it all, but if I can get consistent castings, that is really all I want.

Your success rate seems quite good.

.

 

[creast]

Progress is slow but that usually is the case.
The last couple of days , when possible, I have machined the power piston apart from final OD skim to fit which will be done on a mandrel.
Broaching the two slots was done on the lathe.
The displacer yoke arms were bent from 2.5mm square brass and the end details dado jointed and soft soldered in place.
In a similar way the pivot boss was all turned and milled in the lathe using my tool post mill attachment and a soldered boss added.

 

[GreenTwin]

Broaching the two slots was done on the lathe.

How did you do that?

.

 

[creast]

How did you do that?

.

I should have taken photos.. lol!
Basically, I set a piece of 1/4" square HSS steel into the tool post and squared it up to the workpiece and set the height so it was dead centre.
The tool had just a basic rake of about 5 degrees.
I use a homemade indexing jig on my Myford which allows me to lock the spindle and index using a 60 tooth gear.
The tool is simply driven into the part using the carriage/saddle movement to shave off a few thou at a time.
It's slow but it saves taking the part off the lathe.
I use this indexing method a lot on the lathe for simple splines, keyway and flats on turned pieces using my rather crude (and not safety compliant) milling attachment.

 

[creast]

Well time flies!
I have still been plodding on, when time permits, constructing the displacer and its cylinder.
I followed on with my initial plan and made the cylinder from stainless with a copper hot cap silver soldered in place.
Lapping the power piston cylinder has been a chore as I have no real suitable lap available so have decided to make one but this time as a helical design.
The pattern has been printed and will be cast in brass. Copper would probably be better but may be too soft when cast to maintain wall pressure.
It's almost at the stage to trial assemble and see if it will run and if it does I can proceed with the pump and firebox,
Fingers crossed

 

[Richard Hed]

Well time flies!
I have still been plodding on, when time permits, constructing the displacer and its cylinder.
I followed on with my initial plan and made the cylinder from stainless with a copper hot cap silver soldered in place.
Lapping the power piston cylinder has been a chore as I have no real suitable lap available so have decided to make one but this time as a helical design.
The pattern has been printed and will be cast in brass. Copper would probably be better but may be too soft when cast to maintain wall pressure.
It's almost at the stage to trial assemble and see if it will run and if it does I can proceed with the pump and firebox,
Fingers crossed

Hold on, Isn't it dangerous to silversolder stainless? I thimpfks it will not hold.

 

[creast]

Hold on, Isn't it dangerous to silversolder stainless? I thimpfks it will not hold.

I have never had a problem silver soldering / brazing stainless .
Where have you seen reference to it being a problem?
Rich

 

[Richard Hed]

I have never had a problem silver soldering / brazing stainless .
Where have you seen reference to it being a problem?
Rich

I have no experience with this at all. The guys on this forum (me thimpfks) have said so.

 

[Chiptosser]

Problem silver soldering Brass and stainless????????????
Not at all.
Maybe someone has had bad luck because of inexperience. Practice practice!

 

[creast]

She runs!!
The lapping tool didn't completely fill on casting but was suffice to get the rather slow lapping process done.
I decided to assemble and see if she would run and despite more friction than I liked for a hot air engine she does run, even on a spirit burner!
I am well chuffed.
Now to finish the pump and firebox etc as well as start the job.

 

[GreenTwin]

Most excellent work across the board, patterns/molding/casting/machining, etc.

Very nice running too !

.

 

[creast]

Thanks Pat.
So far I have mostly enjoyed this project and the challenges it has presented and as you know it is always a learning process that makes it more worthwhile.
Rich

 

[Richard Hed]

Problem silver soldering Brass and stainless????????????
Not at all.
Maybe someone has had bad luck because of inexperience. Practice practice!

Well you guys are correct. I viewed a utub vid where the fellow did stainless silver soldering all the time for a living. It works well. Good to know