A48 Knurled Hinge Pins

[M Towsley]

I want to post this in Everyday Discussion as I don't know if these fit more than the post war planes.

I just got off the phone with Tom at Wag-Aero, (very nice guy). While speaking to him about landing gear bushings he told me he was in the final process of having part number A48, the knurled hinge pins, manufactured and should have them by sometime next week. Price is to be announced, but expect around $5-$6 each. I know this has been a past topic and for those of us who do not know how to knurl, etc., at least there is a source for these, now.

[3Dreaming]

Re: A48 Knurled Hinge Pins

Marty, without looking it up is that the long pin or the short one? I hope they decide to make both long and short.

[M Towsley]

Re: A48 Knurled Hinge Pins

Not sure, Tom. I can dig out my schematics and see if it is listed. I can ask Tom at Wag tomorrow if they plan on doing the other. Part number would help.

Stupid question, where does the long and short go so I can advise him.

[M Towsley]

Re: A48 Knurled Hinge Pins

A-48 is for the rudder/elevator hinges. I do not have the aileron schematic to show what part number that pin is.

[Robert Lees]

Re: A48 Knurled Hinge Pins

Marty, you & I really need to speak more often.

Take standard AN394-51 pins, and get them knurled. OPP.

This works for elevator & rudder; I went a different route for the short aileron pins.

[M Towsley]

Re: A48 Knurled Hinge Pins

Ah, Rob. There is the problem. Where do you have them knurled? I don't find that in the phone book hereabouts in my part of the country.

I was thinking of asking Tom at Wag-Aero who is knurling their pins, but thought that was a bit tacky.

[Robert Lees]

Re: A48 Knurled Hinge Pins

Actually I didn't have them knurled, but my friend had them done at his local knurling shop (really). Any half-decent machine shop will know a knurler.

Perhaps all American knurling is done in China now? Or is nothing made in America now? [/Cessna]

The above friend might be interested in forwarding on "kits" of elevator/rudder knurled pins with fresh bushings...under OPP regs of course...do you think there'd be a market? I post this here openly and without prejudice.

Rob

[Guest]

Re: A48 Knurled Hinge Pins

Use the standard AN part and put Locktite or an equivalent thread/stud/sleeve locking compound on the end where the head is.

[M Towsley]

Re: A48 Knurled Hinge Pins

I would be interested, Rob. However, there seems to be guys here who know how to do it or know someone, (or don't care if they are knurled).

All of my elevator/rudder pins are smooth and move. I was unaware of the knurling until I did some further research on this. (And I found your Loctite tip while researching this, Dave. Thanks)!

[cvavon]

Re: A48 Knurled Hinge Pins

Marty any one with a metal lathe can do knurling all it takes is a tool that runs on the part and expands the metal leaving the marks on the part.

[Hank Jarrett]

Re: A48 Knurled Hinge Pins

http://www.youtube.com/watch?v=dTmv_kYimrI

Not a big deal. I can do it in my garage with a tool that costs less than $100 on my lathe. I didn't use knurled pins on my plane (there weren't any on it when I bought it) and I usually make a point of moving each pin on pre-flight when I inspect the surfaces. If the surface moves easily, but the pin doesn't, I note to pull that pin and free it up next chance I get. I like my way better since the pin rotates freely with reference to BOTH sides of the hinge. I get more warning to fix it where a knurled pin is locked to one side and if it were to seize up, the surface would get stiff.
Neither way is likely to get you killed, but mine gives more warning.
Hank

Of course "LEGALLY", if a knurled pin is required, I am probably out of configuration conformance.

[Guest]

Re: A48 Knurled Hinge Pins

I am not sure that I follow what you are doing Hank but regardless I can say that the pin should not rotate in both halves.

It is a mistake to do this or let this situation remain.

The hinge inner half is the wear part and it has the replaceble bronze bushing whereas the outer half must be replaced by welding in a new hinge.

Big difference in maintanence costs.

Dave

[Robert Lees]

Re: A48 Knurled Hinge Pins

As an aside, but on-topic, the Germans use similar pins for their Grob range of aircraft and motorgliders on flaps, ailerons & elevators. I think the Mexicans also do with the Ximango motor gliders.

But they use a scroll pin driven through a drilled hole through the part of the hinge that mustn't rotate, in the same way as CG Taylor used the scrolling to prevent the pin rotating in the wrong part (if that makes sense).

In other words, and in our case, the bronze or oilite bushing is meant to take the wear. If the pin rotates otherwise, it will eventually wear out wot is not supposed to wear.

Wish I had photos....

[Hank Jarrett]

Re: A48 Knurled Hinge Pins

I get what you guys are saying. I honestly hadn't looked at it that way. I forgot that the inner lug was the only one with bushings.

Next change....Put in knurled pins. Unless my A&P/IA wants me too NOW, I will do it AFTER I get back in the air. I doubt it will be a problem in the short term.

Hank

[3Dreaming]

Re: A48 Knurled Hinge Pins

I get what you guys are saying. I honestly hadn't looked at it that way. I forgot that the inner lug was the only one with bushings.

Next change....Put in knurled pins. Unless my A&P/IA wants me too NOW, I will do it AFTER I get back in the air. I doubt it will be a problem in the short term.

Hank

Hank, if I was you IA I would make you change them. If the pin rotates you are wearing the part out, and making the hinge points loose. I have seen some that were really bad requiring welding on the elevators or replacing the brackets on the ailerons.