Flexible drive shafts

I'm thinking about cobbling together something that will involve the use of
a flexible drive shaft. I've found several manufacturer's web sites with
specs about max torque. But not much about RPM.
I figure that max RPM (for most applications around 3600, maybe up to 10K)
is dependent on friction losses. Which are dependent on bending radius.
Anyone have a link to some simple design rules (I'm not an ME) for flexible
shaft applications and RPM/friction losses?
Reply to
Paul Hovnanian P.E.
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It's been quite a while since I've worked on a project involving high speed flexible shafts, but Suhner and SS White seemed to be the leaders at that time. This is Suhner's page on flex shaft design.
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Reply to
Ned Simmons
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Reply to
Spehro Pefhany
In article , Paul Hovnanian P.E. writes
The Dremel flexible drive will work at high speeds; I guess the torque it can handle is fairly low.
Reply to
Chris Holford
You tawkin about car drive shafts, or Foredom/Dremel and those? I have a Foredom, and it is a nice one. The friction losses and things that slow rpms are more a function of type of materials being cut, the force of the hand of the person feeding the tool, the tool, the diameter and/or surface area of the tool, and a couple of other things. There's a million little tools that go on there, and they all perform different. The little dentist drill sized tips will run and sustain higher rpms than the larger carbide cutters of say the 1/4" and larger. You just have to play with it. I also think it's your unit. My daughter got me my Foredom for a nice 8' tall double entry gate I made for her, and both of us thought we got the better deal. Of course, $400 later in bits, I think she did, but that was after the original trade of oranges for oranges.
Reply to
Steve B
Flex shaft tech is more for low-torque applications, they can be run at fairly high speeds, see Foredom flex shaft tools for example. Friction losses are pretty high, the flex housing on my Foredom gets pretty hot after a long session. With today's rare earth magnet motors, there's not a lot of call for using flex shafts for what they used to be used for, you can drive stuff directly with small motors. And all those old applications that had flex shafts stuck into panels for remote manual controls can be done electronically. If you're trying to transmit significant power, find another way, flex shafts aren't for heavy moving.
Haven't seen any books on flex-shaft design and I pretty much went through all the old stuff at the university library back when. The manufacturer's specs and customer app staff are what you've got now.
Reply to
Other high speed versions are on gas grass trimmers and tree limb trimmers.
Those engines are often used in model airplanes. Large biplanes use two!
I have a Foredom 1/4 HP unit on a flex. There is some power in it.
Reply to
Martin Eastburn

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