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[TowerTalk] Welding Chrome Moly

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Subject: [TowerTalk] Welding Chrome Moly
From: (Bill Coleman AA4LR)
Date: Tue, 1 Jul 97 21:59:42 -0400
On 7/1/97 21:22, Kenneth Mathews at wrote:

>I have read the postings on drilling Chrome moly and wonder if anyone 
>has thought about having a bead of weld put down both sides of the 
>mast that will go into the rotor mount and help keep it from twisting in 
>the mount due to the torque.  Does anyone have knowledge of how 
>to and what type of welding to use of this type of material.

Just so happens....

4130 chromemoly steel has been an aircraft building material since 
shortly after the Wright brothers perfected their all wood and wire 
designs. Typical tubing sizes are around 3/8 to 1 inch and a wall 
thickness from 25 to 150 thousands. Not the typical tubing you find for 
tower masts, but the same metal.

Oxy-Acetyline torches are the classic method of welding, although 
production lines (eg Piper aircraft of the 40's and 50's) typically use 
TIG (Tungsten Inert Gas). Either method would work in your case.

Good quality welding rod suitable for 4130 is typically used, however, 
many of the racing planes from the 30's used whatever they could scrounge 
(read steal) up. 

Welding thin-wall 4130 tubing takes a fair amount of skill, but you are 
talking about running a simple bead down a thick-wall mast, which isn't 
as critical. In short, anyone familiar with a welding rig should be able 
to do this for you.


One problem I can see with this idea is that the bead may be poorly 
positioned in the rotator clamp and actually reduce the contact area.

If clamp slippage is a real problem, perhaps you might consider some kind 
of torque dampener?

Bill Coleman, AA4LR, PP-ASEL        Mail:
Quote: "Not in a thousand years will man ever fly!"
            -- Wilbur Wright, 1901

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