Annealing 4130 after work hardening

[svyolo]

I am trying to remake a couple of kit parts slightly different than the kit to move the aileron cable pulleys a half an inch, the ones that send the cable down the strut. I don't really have the equipment to properly bend 4130 that thick (1/8"), so my choices are welding or cold forging with a hammer and big bench vise. I made the first one by hammering, but am sure I work hardened the steel. Do I need to anneal the steel? Does 4130 get brittle? A google search didn't answer my question. I was able to find out how to anneal it, but not if I need to.

[alaskabearhawk]

As long as you have the proper bend radius and don't pound the crap out of it, you should be fine. Unrelated part, but same idea. Use a smooth block with the proper bend radius...and smooth jaws in the vise.

http://www.mykitlog.com/users/display_log.php?user=yeeeha&project=527&category=3675&log=141343&row=34

[spinningwrench]

There is plenty of reference material online about bending normalized 4130 steel, generally you want a minimum bend radius 3X the thickness of the material. Your bend should be transverse to the rolled direction of the material.

[svyolo]

Bend radius is good. But I did pound the crap out of it, one direction only. I didn't have to "go backwards", or whatever the technical term is. I didn't over bend, and have to bend back. My bend radius turned out slightly larger than than the kit parts.

It is 3/4 by 1/8 stock. It started out as 1" width that I cut down to 3/4". I think 4130 gets a bit stronger by work hardening, but I don't know if it gets brittle.

[alaskabearhawk]

Well, bending any 4130 is harder than Chinese arithmetic, especially the thicker the material. The hammer that I use is a heavy polished face ball peen hammer with a short handle, actually more like a mini-sledge hammer. Size matters and the more mass the better. (see pic) It's my favorite.

Like spinningwrench said as long as the grain is running in the proper direction you should be fine.

20211121_224714.jpg

[Mark Goldberg]

Check any 4130 you have bent up and are worried about with a 10X magnifying glass. You will see any cracks with that. Mark

[Nev]

I am trying to remake a couple of kit parts slightly different than the kit to move the aileron cable pulleys a half an inch, the ones that send the cable down the strut.

Very good idea. Mine didn't line up with the strut either, and now contemplating how to fix it. Could it be done by welding over the hole and re-drilling it in the correct place ?

Also the trim cable in the cockpit touches the aileron cable. The easy fix is to raise the trim cable fairlead, which currently pulls the cable down and causes the issues. Has anyone tried raising it by cutting and threading both ends ? Not keen on welding now with all the avionics in.

[svyolo]

The very easy fix for the pulley, is a smaller pulley. Unfortunately they don't come in a lot of sizes, at least shopping on Wickes and ACS. The next size down from 3", is 1.75": It works, but is a pretty tight radius for 1/8" cable. It might cause a little extra friction, which is the last thing you need more of in the aileron cable loop. It might be what I end up using, but I thought I would try just moving the bigger pulley while I am working on finishing the wings.

The 1.75" pulley (same ones as the aileron and flap pulleys on the bottom of the fuselage) moved the cable about .6 inches, which was enough. I think I want the cable to enter the strut as high as possible, so I think I am going to try to move the bigger pulley .4 or .5 inches. I won't be able to tell for sure until the next time the wings go back on.

For the aileron/trim cable I added another fairlead on the rear skylight former, moving the trim cable out of the way. Probably a little extra friction as I moved it a lot, but friction is probably a good thing on the trim cable.

[svyolo]

Thanks for all the responses.

[svyolo]

Very good idea. Mine didn't line up with the strut either, and now contemplating how to fix it. Could it be done by welding over the hole and re-drilling it in the correct place ?

Also the trim cable in the cockpit touches the aileron cable. The easy fix is to raise the trim cable fairlead, which currently pulls the cable down and causes the issues. Has anyone tried raising it by cutting and threading both ends ? Not keen on welding now with all the avionics in.

I don't think my kit parts have enough space to move it the amount I think my pulleys need to be moved. I think I initially wanted to try a 2.25" pulley, but couldn't fine them anywhere. I chose that because I thought about 3/8-1/2" was the amount I wanted to move the cable.

The first one turned out OK, the second one not quite good enough, hopefully the third will be a good one. I used the bigger hammer method. Much better.

[gregc]

I went with the smaller pulley and it didn't seem to make a noticeable difference in feel but I am very interested to see how adjusting/moving the bracket works.

[Bcone1381]

Could a small pulley could be installed at the top of the strut to guide the aileron cable down the center of the wing strut without rubbing? AN220-1 is for 1/8" cable and has a groove diameter of about 1.25".

This thread is about annealing....but its drifted a bit to pulley's, so if I'm hi-jacking it I apologize....

[gregc]

I think you mean adding an additional pulley. Assuming you could, would the combined friction of the larger pulley with the +/- 40 degree change of direction plus a smaller pulley with say a 5 degree change be less than simply using the small pulley in the first place? I have no idea but I suspect we are talking about very small differences.

[svyolo]

I don't know that the smaller pulley actually does have much more friction. For small turns like the bottom of the fuselage I am 100% sure they are fine. I am not a pulley expert I am open to doing either, and am making the new brackets for the bigger pulleys, match drilled to the kit brackets so they use the same kit bolts. FWIW the lower aileron cable pulleys are 2" in diameter, but use a -4 bolt, where the upper ones use a -5 bolt. The 2 inch pulley would be a bit bigger, but you would have to bush the bracket hole down to 1/4". I may give Bob a call.

[svyolo]

I just tried doing a little homework on the subject. I couldn't find anything in AC43. I did find some engineering references for pulley size vs size and type of wire. Several references were identical. For 1/8" 7X19 wire, the "normal" minimum pulley diameter is 3". The "critical" minimum is 2.25". None of them referenced the amount of angle that the cable changes direction. I would guess small angles like the bottom of the fuselage smaller is OK.

[Nev]

The very easy fix for the pulley, is a smaller pulley. Unfortunately they don't come in a lot of sizes, at least shopping on Wickes and ACS. The next size down from 3", is 1.75": It works, but is a pretty tight radius for 1/8" cable. It might cause a little extra friction, which is the last thing you need more of in the aileron cable loop. It might be what I end up using, but I thought I would try just moving the bigger pulley while I am working on finishing the wings.

Today I tried a smaller (1.75") pulley at the top of the strut. This fixed the problem completely. However on the AircraftSpruce website they say "The low allowable load lim it of the -1 pulley is based on cable fatigue. When used on frequently used aircraft controls the cable wrap angle should not be more than 15 degrees from a straight line."

However as Svyolo points out, the pulley at the bottom of the strut is 1.75° and this changes the direction by about 25°. What are your thoughts on this ?

[gregc]

Today I tried a smaller (1.75") pulley at the top of the strut. This fixed the problem completely. However on the AircraftSpruce website they say "The low allowable load lim it of the -1 pulley is based on cable fatigue. When used on frequently used aircraft controls the cable wrap angle should not be more than 15 degrees from a straight line."

However as Svyolo points out, the pulley at the bottom of the strut is 1.75° and this changes the direction by about 25°. What are your thoughts on this ?

The Ralmark site (https://www.ralmark.com/) has useful data on their pulleys. The 1.75" pulley (MS20220-1) has a load limit of 500 lbs. Does the rigging tension + aerodynamic control load + change due to temperature + safety factor exceed that? I think we need some input from Bob/Mark or another expert.

[svyolo]

Today I tried a smaller (1.75") pulley at the top of the strut. This fixed the problem completely. However on the AircraftSpruce website they say "The low allowable load lim it of the -1 pulley is based on cable fatigue. When used on frequently used aircraft controls the cable wrap angle should not be more than 15 degrees from a straight line."

However as Svyolo points out, the pulley at the bottom of the strut is 1.75° and this changes the direction by about 25°. What are your thoughts on this ?

I think all their pulleys have the same disclaimer. I am not sure what to make of it. I know if the pulley is very small, it should probably only used as something better than a fairlead. Based on Bob's choice of hardware and bolt size, I kind of think the only reason we are using 1/8" cable for the flight controls is for extra wear resistance. Unfortunately I am below a layman on this, so I am going to call Bob in a few minutes.

Here is a chart of pulley size vs cable diameter and type.