Tailwheel Tire Wheel Bolt Torque

[8164]

My first post in this group. Just bought a 1947 140, though I also owned a '46 120 for several years. I'm not new to the type and, though I'm not an A&P, I worked many years as a mechanic's assistant on warbirds and Ive worked on my planes for a long while, under the supervision of A&Ps and I/As.

Having said that, I thoroughly searched through this forum (and the many, many discussion of the Scott 3200 setup) and I cannot find this piece of information:

1. What is the torque value for the four (4) AN4 bolts that hold the two wheel halves together on our 140's (using a Scott 3200)?

Alaskan Bushwheels (the now owner of the Scott 3200) publishes a 1-sheet instruction which says, "Torque AN4-34A bolts to 120 in-lbs." I'm using the AN4-7A bolts, though I assume that's essentially the same. Is that the torque you folks are using?

2. What is the proper inflation of the 2.80x250 tailwheel tire? Alaskan says 25 psi. Other here say 45 psi, still others use 55 psi. I'm curious what the general consensus is.

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Thanks!

Marc C. Lee
N2323N

[6643]

Absent a value from either Cessna or Scott, use the torque chart (Table 7-1) in AC43.13-1b. The answer there is 40-70 in-lbs. I'd use 70.

As far as pressure, I use 30psi, which I think is the minimum Scott recommends. The loading, at least with the early, straight legs, is less than 100 lbs.

(Where do you find an AN4-34 bolt in a tailwheel? 120 in-lbs is higher than the maximum of 100 recommended in AC43-13.-1b. It would be OK for an AN5 bolt...)

[V529]

Like John wrote, 30psi on the tire. I ran mine at 35psi. Those tires like to come off the rim, spin or something. Occasionally people have flat tail wheel tires. Better to have a few extra pounds than not enough.

[6183]

My first post in this group. Just bought a 1947 140, though I also owned a '46 120 for several years. I'm not new to the type and, though I'm not an A&P, I worked many years as a mechanic's assistant on warbirds and Ive worked on my planes for a long while, under the supervision of A&Ps and I/As.

Having said that, I thoroughly searched through this forum (and the many, many discussion of the Scott 3200 setup) and I cannot find this piece of information:

1. What is the torque value for the four (4) AN4 bolts that hold the two wheel halves together on our 140's (using a Scott 3200)?To be perfectly honest I can't find anything that discusses torque value for the AN4-7A bolts that are utilized to bolt the two wheel halves together. I even looked in my old US Army L-19/0-1 manuals, and the publication only says to tighten the nuts securely without any torque value. Therefore, what my fellow moderator John Cooper has recommended about utilizing the torque chart as found in FAA AC43.13-1b will be a good choice. I agree with the 70 in-lbs as John has stated.

Alaskan Bushwheels (the now owner of the Scott 3200) publishes a 1-sheet instruction which says, "Torque AN4-34A bolts to 120 in-lbs." I'm using the AN4-7A bolts, though I assume that's essentially the same. Is that the torque you folks are using? AN4-7A are the correct bolts for the Scott 3200 as per Scott Aviation. AN4-34A bolts utilized by Alaskan Bushwheels is for a much wider wheel and tire configuration than found on the standard Scott 3200 type wheel, use the AN4-7A bolts.

2. What is the proper inflation of the 2.80x250 tailwheel tire? Alaskan says 25 psi. Other here say 45 psi, still others use 55 psi. I'm curious what the general consensus is.This question comes up from time to time, and it really depends on how much weight is imposed on the tailwheel from the aircraft. What the weight is on my tailwheel assembly for example, is not the same for all aircraft of this series. Items like landing gear extenders and additional equipment adds weight to the airframe that is different from when your aircraft was originally manufactured. Cessna 170's for example, had a placard/decal in the glove box that said used 35 psi in the tailwheel tire. Here's a Scott tire pressure chart from our friends over at the C-170 Association.]



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Thanks!

Marc C. Lee
N2323N

[6183]

Here's a Scott Tire Pressure Chart for pneumatic tires posted by our good friends over in the Cessna 170 Association. https://forum.cessna170.org/forums/down ... &mode=view

[8164]

Thanks, Mike. I'll try the 75 inch pounds. That sounds correct from an armchair perspective

[6643]

I'll try the 75 inch pounds.

Maybe a typo, and probably not critical, but the recommendation was 70, not 75.

[8164]

Thanks John. I did 70.

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