A question for 1/2a historians.
#1
Thread Starter
A question for 1/2a historians.
In looking at some of the older half A engines that I have sitting around I've noticed that they all seem to have a propeller shaft that has a 5-40 thread. My sample is a bunch of Cox engines, a couple of OK Cubs and a Baby Spitfire. I'm wondering if there was a specific reason for using the 5-40 thread. Was it a more common thread at the time? It seems like using a more common thread like the 4-40 would reduce production cost.Any engine historians out there?
#2
I am not a Cox historian but have a question
What make you believe a 4-40 was more common in 1940s?
And do remember......if a customer needs a special part that you sell....modest price increase for the convenience is translated to profit...something every good business desires and needs
What make you believe a 4-40 was more common in 1940s?
And do remember......if a customer needs a special part that you sell....modest price increase for the convenience is translated to profit...something every good business desires and needs
#3
Thread Starter
I am not a Cox historian but have a question
What make you believe a 4-40 was more common in 1940s?
And do remember......if a customer needs a special part that you sell....modest price increase for the convenience is translated to profit...something every good business desires and needs
What make you believe a 4-40 was more common in 1940s?
And do remember......if a customer needs a special part that you sell....modest price increase for the convenience is translated to profit...something every good business desires and needs
#4
A 5-40 was a standard size. It still is. It is a 1/8" stove bolt thread, meaning an 1/8" hole drilled for the prop would be right. Later on the 1/4" 28 UNF (fine) became standard for the larger motors even for the Japanese who had been using metric for a while.
#5
Thread Starter
Yes,I would bet that the convenience of a common size hole for mounting the prop was probably the main factor. After I started this thread I found an article on the front page of the Model Engine Collectors Association website. It discusses the early days of half A glow engines in the late 40's to early 50's. Early on it was a pretty competitive market among several manufacturers but they tended to use the same props so I would think that the 1/8 inch hole and as a result the No 5 screw just ended up as the de facto standard. It's probably not that important. I'm just entertained by finding out the origins of things.