Mount Trapezium

[redhouseluv]

Hi Jason

That sounds like a plan, can I just confirm before proceeding:

1. As the 2 halves are bolted together, there is no need to soft solder?
2. The boring and the outer radii are machined on the milling table?
3. Better to have one half tapped and the other clear rather than both clear? Which side is tapped (spigot side or the other?)
4. The holes sizes in the lugs are given as 2.3mm so in the Imperial world I should be looking at 8BA?

[Jasonb]

1. I seldom solder them.

2. Boring can be done on the lathe but light pressure if using the 4-jaw as it is easy to distort the soft gun metal, alternative is clamped to a faceplate or flat bar held in the 4-jaw. I sometimes will use a boring head and do them on the mill but I don't bore them with the R/T. OD is OK with the rotary table and you will likely have to finish off with a file due to screw heads

3. Personal preference if you tap one side or have clearance in both unless you have a prototype to replicate.

3. Yes 8ba

[redhouseluv]

Perfect, thank you, lets see what I can come up with! 

[redhouseluv]

Just finished the strap and very nearly wrecked it......

It fitted and moved beautifully with the sheave up until I put it in the 4-jaw to machine the spigot. I must have deformed it slightly and it took forever to get it back true and running without any tight spots. Still lesson learned without ruining the whole thing and scrapping a days effort!

[PaulR]

That looks really good! Great that you were able to save it, all that work down the pan would not be nice.

[redhouseluv]

I just noticed on a photo of a completed engine there's a oil hole in the strap; which makes sense as there is no way of getting any lubrication in there. Strange its not on the diagram?

[redhouseluv]

I spent the day (when not doing my day job) making this very short valve rod. At the end of the day I discovered I had made it using the incorrect method and it should've been made by silver soldering the round bit to the rod - I just went with how I thought it would be made, out of a single piece; it ain't as pretty, but it works.......

Let's keep it to ourselves and nobody will be any the wiser! 

[PaulR]

As long as it's the right length and the hole is in the right place is all that matters, I like this 'authentic' look.

[crueby]

Looks good, however its made!




Um, in your first picture, of the plan for the rod, I hope the view on the right of the picture is for a different  rod, since that view shows an offset to the side?   

[redhouseluv]

Hi Chris

You are correct, it is offset to the side; the build recommends bending the rod on assembly to get the offset distance correct - I must admit I'm not looking forward to doing that!

[crueby]

The drawing shows a LOT of offset for such a short part!

[Jasonb]

I think you will have a job bending that particularly the threaded end which will likely snap off or bend the thread rather than the thicker base of the rod. Or does Anthony mean giving it a slight tweak to get it spot on rather than complete shaping by bending?

I would tend to measure from the part assembled engine and then make from solid. First turning the thread to one edge of some rectangular stock and then putting the hole into the opposite side corner. If you are really up for it two ctr holes sould be included so the middle can be turned but probably easier to saw and file.

[redhouseluv]

I agree, I don't see it bending easily - see the wording (below) from the buildlog

I see it breaking easily 

[redhouseluv]

Pivot rod

I'm making the pivot rod, this is fulcrum for connecting rods and piston rod so fairly critical. I've made the first part (top diagram) but am having trouble with the measurements of the 2nd part. From what I can determine the red arrow is pointing to the actual section where the surfaces rotate, but it gives no measurement (length)?

I have also included the picture of the top yoke which pivots at this location and the general arrangement in case that gives some clue?

Any ideas greatly appreaciated .........

[Jasonb]

You really want it to scre wup tight just before it tightend on the arm so the plain length should be just over the 0.312"

Personally I would make it with a shoulder making the unthreaded section 0.156" for  alength of 0.314" and increase the hole in the arm to the same 0.156"