Throttle Screw Question

[GWRdriver]

I am building a Stroudley-type dome mounted throttle, the kind with upper and lower rotating plates connected by a pair of connecting rods, and I have a question about pivots. The plate pivots (one in each plate) will be 3/16" diam and the connecting arm pivots (two in each plate) will be 1/8" diam. The lower (driving) plate will be SS and the upper (valve) plate will be phos bronze. The pivot pins/screws, whatever those are, will be SS.

My question is this, assuming that the minimal, base-line choice for pivots would be plain shoulder screws threaded into the throttle body and plates, what experience has anyone with other pivot types which might be more secure than a simple thread. I can think of several alternatives, pressed studs with E-rings for instance, but I wanted to know if anyone had experiences in this area and had a simple but effective and widely-used technique.

There will be enough "meat" in the throttle body and plates to do just about anything within reason, including running in radial grubb screws to lock threads.

[chris vine]

Hello in USA,

I am not sure about the pins, I think I would be tempted by something pressed in as it would probably be stronger than theads. Others may think different.

The only thing I would say is that you should probably make the regulator disk from a different material from the block or face it is working against. Maybe stainless against PB.

Chris.

[GWRdriver]

I think I would be tempted by something pressed in as it would probably be stronger than theads. - Chris

Chris,
Although strength is certainly a consideration in this case IMHO security is more important . . . . not having the screws/pins go adrift while in steam. I too lean toward pins, but screws might do plenty well.
I have been told that contrary to what one might think, vis. the "dissimilar metals" axiom, SS and bronze are not good sliding mates. Certainly the lower (driving) disk can be SS but the upper one (I'm told) is just as well made of bronze.

[chris vine]

Hi Again,

In about 20 years you can tell us if the bronze on bronze worked fine!!!!

Chris