springs for an offset rotor head

ronr

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Aug 28, 2021
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klamath fall or
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quicksilver bensen (project)
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150
Hi, I need help from anyone familiar with bensen or ken brock gyros. The instructions that I have say that the trim springs need to be preloaded to 30 lbs but is gives no info on the springs themselves. If anyone can give some info on the length and size of the springs and a supplier it would be appreciated.
 

Jazzenjohn

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Oct 9, 2004
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Milan Mich.
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I've designed, built, and flown 4 different ultralight gyros. Amassing parts for a 2 place now.
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Generally the springs are about 6 to 12 inches long and 3/4" to 1" inch diameter with a wire size of about .035. If you pull it it takes about 30 pounds of force to deflect it a few inches. Lots of springs have been used, often from the local hardware store. There will be a certain amount of trial and error getting it set up depending on the spring, the rotorhead offset, and the rotor blades.
 

Hydro Pilot

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Apr 12, 2011
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San Antonio, FL
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Single seat dominator
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>300 Hrs
I suggest that you make a bracket that you can slide up or down on the mast o adjust it. Connect the spring to this bracket. It should have some backpressure to begin with. After you fly, adjust it to find the sweet spot.
 

ronr

Newbie
Joined
Aug 28, 2021
Messages
6
Location
klamath fall or
Aircraft
quicksilver bensen (project)
Total Flight Time
150
thank you, the print dose have an adjustable clamp on the mast. One other question, if you preload the springs to 30 lbs with the stick full back and then do a hang test should it end up in about a stick neutral position?
 

Jazzenjohn

Gold Supporter
Joined
Oct 9, 2004
Messages
2,958
Location
Milan Mich.
Aircraft
I've designed, built, and flown 4 different ultralight gyros. Amassing parts for a 2 place now.
Total Flight Time
400+
The spring wont effect the hang test, it comes into play when the rotors are turning at flight speed and balances the rotors lift vs the offset on the gimble. To get the rotorhead into the mid position for the hang test, use a shim that is half the full travel to the stop and put it in the front, it should be about 1/4 inch or so thick.
 
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