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springs
mwilli7119:
on page 37 of the VE O-235 engine installation plans in paragraph 3 springs are mentioned to return the mixture and throttle controls. What size springs do I use. the only numbers I can find are C161 and Century Springs says that those are compression springs. these should be extension springs.
thanks in advance.
Mike
Anonymous:
On a related note, worth bringing up again...
I don't know if this is a new installation, or if you are replacing previous springs. Assuming you are using the Ken Brock "carb control bracket" (CCB) I believe there has been at least one incident/accident which occured after one of the springs pulled free.
As originally installed, the hard steel springs pulling against the aluminum CCB have a tendancy to "cut" there way through the aluminum holes through which the springs insert in the CCB. There are a few fixes for this, one of which at least is to install a small machine screw through the hole in the CCB with a locknut holding the screw in place. Before torquing the screw down, lock the spring hook around/under the screw. With this method, the hard spring pulls against the steel machine screw, which itself is torqued tight against the CCB.
This may not apply to you, but this is one of the things that needs regular inspection on our birds.
Drew:
You might want to also check out the thread "throttle_mixture controls" on this site.
Anonymous:
--- Quote from: "Anonymous" ---On a related note, worth bringing up again...
This may not apply to you, but this is one of the things that needs regular inspection on our birds.
--- End quote ---
Key words, regular inspection. I had a throttle failure in a Quickie and got lucky when I kept some power. After that event word went out to add a spring to default to the full power side on those pissant Onan engines.
You just want a very light spring to default to full rich and full throttle. Spring failure rates are pretty damn low compared to other hardware. Name the last time a garage door spring failed? If it did, how many ops did it have.
Burt likes springs for a very good reason.
Jack
Dan Patch:
I believe there has been at least one incident/accident which occured after one of the springs pulled free...
Correct, and your summary of the problem is quite accurate. I remember it very well.... since it happened to me! :shock:
By pure good luck, nothing got bent, and I didn't even know I had a spring failure until applying power to taxi clear of the runway after landing. (Power? What power?) A full description of the "whys and what happened and the fix" can be found in the Canard Pusher, CP65, Oct. 1990 - it's too long to reproduce here. One good approach to preventing this type of problem (spring resonance sawing through an Al bracket) is nicely outlined above.
There is another point that should be mentioned, however. If you rely on a single spring and it breaks, for whatever reason, you could be out of business, depending on the specifics of your installation. (BTW, every one of the four springs on my garage door has broken at least once, some twice, and no vibration involved! - I agree, a lotta ops though.) So anyhow, I originally used two springs in parallel thinking that I had redundancy. But it turned out that neither spring alone was quite strong enough to pull the throttle open on its own (because of the force needed to drive the accelerator pump on my Cont. O-200), so that my 'redundant system' actually turned out to be TWICE as likely to fail! So whatever you decide to do, (I'm currently using a three-spring, damped system), try to be sure that your throttle and mixture controls aren't subject to either single-point or to 'double, single-point failures'. 'Zero, single-point failures' is a lot better plan! :)
Oh, and you are right about the required springs being extension, not compression springs.
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