Warbird Information Exchange

Hi.. I'm working on a Harvard 4 ground up resto & have a question I hope someone can explain about the size of the elevator control horn bearings used & p/n prefixes?

To give a brief background, this project basically arrived in boxes of many mixed up Harvard & Texan parts from many different models. The aircraft is still a little incomplete but on the other hand I have multiples of some items.

Anyway, according to the Harvard 4 IPC, the elevator control horn should be p/n 66-52205 with Fafnir K4 (1/4 bore) bearings fitted.
The control horns that came with the project are as follows:

p/n 52-52203, fitted with K5 bearings (5/16 bore)
p/n 88-52203, fitted with K5 bearings (5/16 bore) and much thicker walled forging in many areas than the one above
p/n 19-52203, fitted with K4 bearings (1/4 bore) and again thicker forging

Now, my questions.. can anyone tell me which bearing size came first?.. the 1/4 or 5/16 bore, or did Canadian Car & Foundry maintain the 1/4 bearing when North American changed to 5/16 at some point?.. if they actually changed at all?

Also, can anyone explain what the two numeric p/n prefixes relate to? Does a higher number mean a later type design or is it just something like a different supplier code? From my experience most US WWII aircraft types had only a single two numeral p/n prefix.

I'm guessing this is going to be a tough couple of questions, but any thoughts appreciated!

Jason

I can't really help with the first part, but the two number prefix refers to the North American model that the particular part was introduced on.

The higher the prefix number, the later the part was developed.

For example, the '19-' parts were developed for the BT-9, the '52-' parts were from the SNJ-1, '66-' is the Harvard Mk II, etc.

_________________

We have K4 and K5 bearings available if anyone needs them.

ATB,

G

_________________
BURMA! Sorry, I panicked

Hi Jason-

The G parts book (1T-6G-2) shows 88-52205 as correct for the T-6G
The D parts book (1T-6D-4) shows 88-52205 as correct for the T-6D, T-6F, SNJ-5, SNJ-6

I don't have the earlier books here at home but I concur with the other poster that a common suffix with a lower numbered prefix is for an earlier model "T-6". I was involved in a T-6 parts business for about 5 years and tried to make some sense of it as we had our parts organized in numerical order. There were parts that you could find as 55- (T-6A?) , 88-(T-6D/F) and 121 or 168-(T-6G). There were exceptions of course and I never did completely figure it out. We built a T-6F from the ground up during this time from a fairly complete project. There were times when I needed to pull parts off the shelves to support the project and given a choice (interchangeable parts) I would usually take the one with the higher numbered prefix on the theory that the later parts would be updated based on history in service. There were some parts #'s that we had hundreds of and it was fun to see where they failed or wore and to try and figure out why the later parts were changed and how. I found that a horizontal stabilizer would be bad for two reasons; intergranular corrosion or a crack in the forward spar where the fuselage attach forging joins the spar.

Good luck with the project.

Ken

Could you have Wirraway or Boomerang parts mixed in? Maybe they used NA-50 or P-64 designed parts???? Just a shot in the dark...

Hi.... thanks to all for your input so far.

BDK... yes, I have since discovered that the 19- p/n elevator horn (with the smaller K4 bearings) I have is in fact Wirraway.

At any rate, I have decided to go with the thicker forged Fafnir K5 bearing'd horn because that will allow me to use the correct p/n elevator trim pulley brackets that I have. I just need to change the horn mounting brackets because they are also different between K4 and K5 bearing'd horns.

Regards
Jason

I was wondering why you would mention Wirraway when it was a Harvard 4.until I realised Jason is in Sydney! (Yeah more with the eyes less with the brain!!)
The exRNZAF MKIIA Harvard project I was involved had mostly 88- and I think 56-if I recall correctly.

Hello Jason,

This may help you, it is a pretty large file, if you have trouble downloading it let me know. I am in the process of working on version 2 of the companies web page which will have a lot more manuals and also the large PDF file problem fixed. The link below is for the full North American Interchangeable Parts Catalog for all the BC-1,AT-6, SNJ, Harvard aircraft, also if you go to the second link it is for the archives section with a few other manuals that may be helpful.

http://www.legendofaces.com/Archives/PD ... atalog.pdf

http://www.legendofaces.com/Archives

Patrick

_________________
"Preserving history one rivet at a time"

Warbirds of Glory Museum
North American B-25J 44-30733
North American B-25J 44-28898

http://www.Sandbarmitchell.org
http://www.facebook.com/Sandbarmitchell

Legend Of Aces Aviation
North American NA-64 3456
North American NA-64 3434
North American NA-64 3448

http://www.Legendofaces.com
http://www.facebook.com/Legendofacesaviation

I'll take the Wirraway control horn off your hands if you like Jason...