Trim Adjustment Screw - B12-406

[TimHicks]

Re: Trim Adjustment Screw - B12-406

Spare parts:

[astjp2]

Re: Trim Adjustment Screw - B12-406

I could use one or two of those to build patterns from!

[anotherstevest]

Re: Trim Adjustment Screw - B12-406

I would be nice if the thread profile turns out to be one of the unified thread standards but that is not typical for leadscrew applications...

@TimHicks - are all those "spare parts" your spare parts? When someone earlier suggest I just by an elevator is that because someone has one available to sell? My t-cart has generally been so reliable I haven't had to look for many parts (been flying it since 1986...).

Steve Stearns
BC12D N43732
Boulder CO

[anotherstevest]

Re: Trim Adjustment Screw - B12-406

Well, best I can tell the thread profile IS standard. My example part measures as 0.5-13 (UNC). If there is a place to post a .pdf here, I'll post my first draft part drawing. I've attached it here as well. This is an untested draft...

Steve Stearns
BC12D N43732
Boulder CO

[astjp2]

Re: Trim Adjustment Screw - B12-406

I was thinking that the threads were pretty common, not much was very special in 1941 when it was designed. Tim

[TimHicks]

Re: Trim Adjustment Screw - B12-406

Sorry for the confusion. Those "spare parts" are not mine. They belong to Bob Wagstaff in Laporte Texas. If you search this Forum, you'll find contact info for Bob. He's got a lot of TCraft parts.

[woodmw]

Re: Trim Adjustment Screw - B12-406

Rob referred to brass, DJ referred to bronze, Tim ask which one. I have not seen it answered, so I'll ask again:

What material is the male part? Brass? Bronze? What alloy?

Anyone wish to voice an idea?

[TimHicks]

Re: Trim Adjustment Screw - B12-406

I'm not a TCraft expert, nor a metallurgist, nor a machinist. But I've made plenty parts on mills and lathes (manual and CNC). And I've had a lot of stuff made in machine shops by much better machinists. And some of that stuff has been in brass.
I don't really know the difference between brass and bronze. But I don't think I've ever hear the word "bronze" uttered in a machine shop (maybe "bronze bushing'). And they always have some pieces of brass available for machining.
Maybe the shop's material is bronze and they just call it brass. I don't know.
If I had to hazard a guess, I'd guess that it's brass.

[Hank Jarrett]

Re: Trim Adjustment Screw - B12-406

The word "Bronze" is derived from the Italian "Bronzo" which means "bell metal brass". Brass is a specific kind of Copper alloy made with Copper and Zinc in different percentages. Bronze is a broader term for Copper alloys that are mostly Copper, usually with about 12% Tin and may have Aluminum, Manganese, Nickel or Zinc as metallic additives and may even have non-metals like Arsenic, Phosphorus and Silicon. When Copper alloys were the best and strongest metal available, adding these alloying agents to Copper was the best we had for getting Copper harder, stiffer, more flexible or easier to shape. Not much reason for using them with all the modern alloys available. Where Bronze seems to still be the material of choice is for bushings because of it's anti seizing properties.

[astjp2]

Re: Trim Adjustment Screw - B12-406

A lot of bronze is oil impregnated, many are also sintered, pressed together from small filings under tons of force...tim

[anotherstevest]

Re: Trim Adjustment Screw - B12-406

This task isn't done yet... I'm currently doing investigations to identify the particular alloy of brass that was used. This sure would be easier if we had access to the original fab drawing...

Steve.

[anotherstevest]

Re: Trim Adjustment Screw - B12-406

Can anyone provide me a non-serviceable trim adjustment screw for destructive testing to determine the specific brass alloy?

Turns out the testing organization needs more material than I hoped so I can't use the trim screw I borrowed to make the measurements. And my other one, of course, is still installed in a flying aircraft.

Please let me know if you can. I will post, as I did my drawing, the results so that we may all benefit.

Thanks,

Steve Stearns
Taylorcraft BC12D N43732
Boulder/Longmont CO

[Guest]

Re: Trim Adjustment Screw - B12-406

Steve,

Perhaps you could make one from stainless steel instead.

Certainly as strong. machineability might be an issue.

Dave

[Guest]

Re: Trim Adjustment Screw - B12-406

Another thought, have you looked in MIL Handbook 5 to see what alloys are recommended for aircraft structures?

That may whittle down the options.

ahh... only Copper beryllium and manganese bronzes are included in MIL-HDBK-5. Alloy C17200, that may be your answer. It is the same as AMS 4650 and AMS 4533

Dave.

[astjp2]

Re: Trim Adjustment Screw - B12-406

I would look in the machinist handbook first, the tool engineers handbook second. It is probably just standard brass that they make gears from. You could also check for brass bar stock at McMaster. Tim
Here is one example of what is available

http://www.mcmaster.com/#brass-alloy-464-bars/=yzsa14

and a second

http://www.mcmaster.com/#brass-alloy-360-bars/=yzsaoe

the second would probably be the best.