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JG3

Improved Aileron Bushes

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These are much improved aileron bushes that I made for my Savannah long ago.

1000+hrs now and no wear at all. Still snug fit and silky smooth action.

The larger bearing surface of 8mm diameter Teflon gives no wear on the aluminum.

The bushing is held tight against the support by the bolt, and the aileron bracket rotates on the bushing.

The nyloc nut is used because this isn't a rotating part, and the bushing must be held tight against the support.

Needs access to a lath, but someone should be producing such bushings.

 

4836417_Aileronbushing.thumb.jpeg.ccea39912038b7bd5a7ec7170eb0e28b.jpeg4836417_Aileronbushing.thumb.jpeg.ccea39912038b7bd5a7ec7170eb0e28b.jpeg

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Thanks for that, JG, I remember you describing these.

Despite good intentions, I had done nothing about it...but with sketch now in hand, I shall incorporate these in the next few weeks before attaching the wings.

Are there other pivot points I should be looking at???

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It would be great if more aircraft used bushes like that, no oil = no dust creating grinding paste, clean. Good stuff JG

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I think you should also use a solid spacer inside the bush so there's no tendency for it to tilt in the support piece. Nev

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No tendency to tilt showing after 1000+ hrs. The diameter of the flange for the thickness is plenty stability.

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JG, any comments on which of the bewildering array of PTFE's is more suitable? Thanks........

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Also, suggested thickness of the flange? Thanks again.

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I don't know, probably any would do due to small loads involved. I chose Teflon due to its reputation for low friction.

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Posted (edited)

JG, any comments on which of the bewildering array of PTFE's is more suitable? Thanks........

I was thinking the same thing. I have used pure teflon which is quite soft.

I think a harder mix would be perhaps better for this purpose?

See "Filled ptfe" and "Modified ptfe properties" in link below

https://www.fluorotec.com/news/blog/the-properties-and-advantages-of-polytetrafluoroethylene-ptfe/

Edited by Downunder

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I was thinking the same thing. I have used pure teflon which is quite soft.

I think a harder mix would be perhaps better for this purpose?

See "Filled ptfe" and "Modified ptfe properties" in link below

https://www.fluorotec.com/news/blog/the-properties-and-advantages-of-polytetrafluoroethylene-ptfe/

I just talked to a plastics outfit here, very helpful and they are recommending, quote:

 

A bearing-grade polyester (PETP-GLD130 ‘TX’):

1561422834184.png.5996093153aa69ddca706a22b963a669.png

 

Which is not to disagree with JG's original selection, which obviously works fine, but since I am going to have to source the necessary stock, I'll go with what they suggest....and let you know in 1000hrs how it's standing up.......)

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Also, suggested thickness of the flange? Thanks again.

 

I used 2mm and that works well.

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Ops. Missed this bit:

Sustadur PET GLD 130 is a polyethylene terephtalate compound incorporating a uniformly dispersed solid lubricant. Its specific formulation yields a premium, internally lubricated bearing-grade. Sustadur PET GLD 130 has not only an outstanding wear resistance, but offers in comparison with Sustadur and even lower coefficient of friction as well as higher Pressure-Velocity capabilities.

 

And 2mm for the flange. Got it!

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Take your clues on bushing material from vehicle suspension bushings, they take a hiding.

The aftermarket suspension bushing manufacturers use Delrin (cheapest and softest), HDPE - High Density Polyethylene (better), or UHMW - Ultra High Molecular Weight Polyethylene (the best).

 

https://www.superatv.com/blog/uhmw-bushings-the-ultimate-material-for-better-bushings/

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JG, they may have changed the design slightly on the Sav: the pivot hole in both the Stationary Support and the Aileron Bracket are now 6mm (or slightly over), with the supplied 'tophat' bushing located through both. So the AN3 bolt in your sketch would have nothing to centre it.

 

The manual specifies the following:

The Stationary Support and Aileron Bracket swap positions, depending on which mounting point you are looking at, but the hardware assembly is always the same:

AN3-05 bolt inserted with thread towards fuselage.

AN4 washer between Stationary Support and Aileron Bracket.

Tophat bush SC210 inserted over threaded end of bolt and passing through Stationary Support, washer and Aileron Bracket.

Castle nut and cotter pin.

 

I still think your idea is a better option, but would need to be modified to work with the 6mm holes we now get.

DSCF2096.thumb.JPG.0cc33c1a701d7a2e7f770ab502227d6b.JPG

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I have gone down this same path and had bushes made of similar dimensions for my build.

 

 

Bushes.thumb.JPG.d6ca2dd9d662b80e7b1d3e1759d31d43.JPG

 

Cheers Phil

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I have gone down this same path and had bushes made of similar dimensions for my build.

 

 

[ATTACH type=full" width="506px" alt="Bushes.JPG]43779[/ATTACH]

 

Cheers Phil

Fil65 would it be right to say that your flaperon bushes will effectively 'float' with AN3 bolt and castle nut etc, as per the current Sav assembly instructions, rather than being clamped to the wing hangers, as is the case in JGs sketch? Or did you have some other scheme in mind?

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I just talked to a plastics outfit here, very helpful and they are recommending, quote:

 

A bearing-grade polyester (PETP-GLD130 ‘TX’):

[ATTACH type=full" alt="43758]43758[/ATTACH]

 

Which is not to disagree with JG's original selection, which obviously works fine, but since I am going to have to source the necessary stock, I'll go with what they suggest....and let you know in 1000hrs how it's standing up.......)

Just for consideration. It may be worth considering to use a adjustable reaming tool to get the i.d. of the holes to match perfectly the o.d. of any bushes you are fitting to make a tight / correct fit. I have a mate with a sav and the outer hinges are a loose fit and I have made comment that he should source such or have made these mod pieces so he has them on hand when he wants to fit them. At such time my method would be to use an adjustable reamer to enlarge the holes. That way you sneak up on the hole size and do not drill out over size. Cheers and I like the thinking of JG and others.

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Ops. Missed this bit:

Sustadur PET GLD 130 is a polyethylene terephtalate compound incorporating a uniformly dispersed solid lubricant. Its specific formulation yields a premium, internally lubricated bearing-grade. Sustadur PET GLD 130 has not only an outstanding wear resistance, but offers in comparison with Sustadur and even lower coefficient of friction as well as higher Pressure-Velocity capabilities.

 

And 2mm for the flange. Got it!

 

Bob, I will PM tonight. Perhaps we can get multiple sets made at once?

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Danny just got a new lathe with a nice DRO so that will make it easy to make multiples accurately. he has grabbed some material today so we will have a go at making some as well. We had intended to do when we both got close to that but why not do it now while its in the front of mind...and its a good excuse to try out his new pruchase

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Fil65 would it be right to say that your flaperon bushes will effectively 'float' with AN3 bolt and castle nut etc, as per the current Sav assembly instructions, rather than being clamped to the wing hangers, as is the case in JGs sketch? Or did you have some other scheme in mind?

Bob,

I will be using as per the assemble manual.

Cheers Phil

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It sounds good.

 

If improvements like this makes a good plane better or longer lasting, I would be interested in a complete set of bushes too.

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Great discussion here! JG - thank you for initiating!

My 2010 XLVG is approaching 200 hours and there's noticeable excess slack in the outermost right flaperon bushing and "noticeable" slack in the other seven - progressively less as I work towards the cabin from each wingtip.

IBob, Mark and Danny. Please book a set (8) of whatever each of you produce - I'll pay postage and costs - just tell me where to send the money, and what exchange to use - (Canadian, US or Australian dollars)

Gotta love this site!!!

Fly safely,

Canada Dan

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Hi Dan. I will not be going ahead with the Teflon bushes at this stage:

 

Note that the simple and elegant fix in JG's sketch does not just replace the standard bushes with oversized bushes of Teflon. It also clamps those bushes to the winger hangers with bolts, thereby ensuring that the bearing does not tilt...which will be the tendency otherwise, since the load of the flaperon is to one side of the hanger.

It looks like JGs machine has AN3 sized holes (4.8mm approx) in the wing hangers, but the Savs now have larger holes (6mm approx)

So to clamp a bush centrally to that hole requires a bigger bolt or some such.

So the bush now has a larger OD, and so on.

 

So I thought I'd have a bit of a think about it all before proceeding.

 

It's interesting that Fallowdeer here has a fairly high hour VG with no major wear in the flaperon bushes.

It does look as though ther standard setup has changed since JG's machine was built.

In the case of those standard floating bushes, I wonder if wear may be accelerated by setting them up a bit loose, so allowing the bush to tilt?

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On mine you have to regularly redo the bolts to make sure the bushes dont wear out the alu hangar brackets. I check them every few months and tighten as necessary to make sure the bolt moves and not the bush. This is why I am looking at teflon ones. The teflon style running in a reamed hole in the hangar I think would be a better long term solution but really you need 2 bushes per hangar one either side to balance the load better

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