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Electric Stunt => Gettin all AMP'ed up! => Topic started by: Crist Rigotti on May 27, 2009, 06:47:26 PM
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I took a regular pitch gauge and turned into a reverse pitch gauge for our electric pusher props. I simply turned around the face, attached a new pitch scale, which I drew up using my CAD program, attached the arm, then notched the arm to clear the screw. I've included a .pdf of the new pitch scale full size.
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ANOTHER nice piece of work ! CLP** BW@ CLP** BW@ BW@ 8)
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Why do I begin to get the scent of tar and feathers? S?P
Soon we will seen to be the end of stunt (awki)! ~^
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Crist,
Nice work, I used the Prather pitch gauge were I first set up a tractor prop at the desired pitch then clamped the swing arm and drew a line on the back side at the station I use, then flipped the gauge plate and swing arm around and it worked fine, got the same lap time with both. Your gauge template is what we really needed. Thanks for the great work. I do recommend that when repitching these APCE props (or any prop) that the swing arm be clamped to the gauge plate at the desired pitch setting and both blades be pitched to that point. This gives very accurate pitch, make sure you check each blade as it is cooling down so that the pitch stays as desired.
Best, Dennis T
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Hi Crist,
Nice work on the pitch gauge. I have a few questions: I've seen several mentions of repitching props in various posts. How do you do that? Do you just use a heat gun, how hot, and how much can a prop be twisted from its original form? I have a couple of APC 11-5.5 that I'd like to repitch to 6.5, is that possible?
Also, for you or anyone else, where on the blade do you measure the pitch. I'd expect to measure blade angles between root and tip at several points. The APC E-props have some pretty radical twist near the root end of the blade.
Thanks,
John Witt
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John,
I use a heat gun near the root. I just repitched a 13x6.5 to a 13x3. The 6.5 pitch really is 5.5 on my pitch gauge at station 10. So I repitched it from 5.5 to 3. Use a heat gun near the root and then after a few seconds, twist the blade in the direction you want. Be sure to use a small rag to keep from burning your fingers on the hot blade. BTW after repitching, check your prop to be sure each blade is the same distance when placed on a flat table. I found that when twisting the blade you can bend it up or down.
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John,
When repitching the APC E props you can use a MonoKote heat gun. You can generally move the pitch about 1" +or - from the molded setting. The method is simple but takes a few tries to get the feel for it. I have found that you can select a single station on the blade about 70% of the blade out from the hub. For the 12" diameter I use station 9, for 11" props I use station 8. Next set the swing arm of the pitch gauge to the desired pitch (you mentioned 6.5) at the selected station and clamp it on the gauge plate with a small "C" clamp. This give you the same pitch for both blades without guess work. Next heat one blade near the hub to about 2" out, (flipping between top and bottom every 30 sec or so). I recommend that you get some thin cotton garden gloves for this as the blade gets fairly warm. After about a minute and a half grab the prop hub in your left hand and the blade with the right hand about 2" from the hub (if you are left handed revise this). At this point you tweak the blade in the direction you want the pitch to move. Don't bend the blade just twist it.
This is a developed feel, the tweak is a twisting kind of a pulse, you will feel a bit of resistance, that's about the right place for the first time. Put the prop back on the pitch gauge and check were the pitch is. If you are over you and the prop is still warm you can give it a little half tweak back then check again. If under tweak a second time in the same direction as the first. Once you get the first blade at the proper pitch blow some cool air over the heated area to set the pitch. Go to the second blade and repeat the process. This sounds like more work than it really is once you do it a few times you can usually get it done in 5 minutes.
Best, Dennis T
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Thanks, gents...that sounds like even I could do it.