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Heavy Duty Clamp for Intake Manifold Crossover Balance Tube

Piper J3

Well Known Member
I finished installing High Performance Silicone heater hoses to satisfy the 5-year rubber replacement. I used HPS 7/16" ID, 1 Foot Length, Silicone Straight Coupler Tube Hose, High Temp 4-ply Reinforced, Blue, 21mm OD for the intake manifold crossover balance tube.

I never liked the thin sheet metal Rotax clamps that seal the tube and also provide tension to the spring to the carb vacuum diaphragm housing. I found CHUNYUNGDA TT Heavy Duty Hose Clamps-Diameter Range 20-22 mm, Stainless Steel Solid T-Nuts, Band and Screw for Constant Pressure Hose (5 Pack) for $15 on Amazon. This clamps work perfect to tension the carb spring…
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Jim-

It has be mentioned in other threads that using silicone hose on the Rotax 912 balance tube may not be a good idea for that application. The thought is fuel vapors present in the balance tube may cause the silicone hose to deteriorate and swell over time.

Don't know if that is a real concern or not, but it is plausible ... for that reason I plan on using fuel rated hose at that location when I begin replacing my rubber parts in the next week or so.

Do like the clamp you found ... may look into that.
 
John -

Hose is 4-ply. I doubt if it will swell. It's really stout...
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Jim, Are your carb springs pulling to the side or is it the angle of the picture?

It was my understanding the spring was there to offset the cantilever weight of the carb & air cleaner flexing on the rubber flange.

carb springs.jpg
 
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You are correct - slight angle. Perhaps I'll make a strap similar to original Rotax clamp to maintain CL.
 
I made an offset hook to put spring on centerline with carb. Hook is made from 0.062" music wire. Clamp is rotated to vertical position for quick visual inspection.
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I made an offset hook to put spring on centerline with carb. Hook is made from 0.062" music wire. Clamp is rotated to vertical position for quick visual inspection.
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Isn't experimental aviation great!

We can remove a clamp that has decades of successful in service experience and no known problems, if we don't like the way it looks, and replace it with a beautiful looking clamp and a little piece of music wire that we have no idea whether it will last 10 hours.
I guess having something that should be inspected very regularly is good for keeping our old minds active. :rolleyes:



No offence intended... just interjecting a comment to hopefully spark some thought provocation in all of us, to use when we consider making modifications.
 
Truth of the matter is... I got tired of straightening these out and buying new from Rotax distributors for way too much money.
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