Espritmodel.com Telemetry Radio
Reply
Thread Tools
Old Oct 02, 2005, 08:40 AM
Registered User
Joined Aug 2004
986 Posts
APC SF 9x7.5 prop balance/mount issues?

Has anyone noticed a problem with APC SF 9x7.5 props?
I have mounted/purchased more than a half dozen and all of them have vibration issues. Then when I mount the APC SF 9x6 prop the vibration
goes away, or any other prop for that matter. I have prepared all of the props for mounting in the same manner but continue to find the same results. I do not balance my props before I mount them but it has been my experience that it is very rare (maybe 1 in 20) thatwhen I put a brand new prop on and it has vibration/balance issues. I have never had this problem with any other APC SF props, not even ones with alot of pitch like the 10x7 and 11x7 SF's also this has occurred on two different setups with completely different motors and airframes. Is it just me or what?
shawn
sbmon is offline Find More Posts by sbmon
Reply With Quote
Sign up now
to remove ads between posts
Old Oct 02, 2005, 09:09 AM
Registered User
Dr Kiwi's Avatar
Chattanooga, Tennessee, United States
Joined May 2003
27,197 Posts
I balance EVERY prop I ever use. The APC E's are often a long way out of balance and are sometimes bored off center. Get a cheap (?$4.95) Great Planes handheld balancer, even if you don't go for the far more expensive Top Flight Magnetic one (~$20).
Dr Kiwi is offline Find More Posts by Dr Kiwi
Reply With Quote
Old Oct 02, 2005, 09:14 AM
Registered User
Joined Aug 2004
986 Posts
I agree this will be my next purchase (prop balancer)
but this still has me scratching as far as what is the deal with the 9x7.5's
could the mold for the prop be causing this? Never had this problem with any other
prop before.
sbmon is offline Find More Posts by sbmon
Reply With Quote
Old Oct 02, 2005, 10:00 AM
Registered User
Cincinnati
Joined Jul 2004
616 Posts
The 9X7.5 is the highest pitch ratio SF prop in the APC line. Possibly it's having some flow separation or buffeting type vibration, rather than imbalance related.

Do you notice the associated airframe vibration in flight that an imbalanced prop would cause, or does it seem to go away in flight?


Mike H.
Dynomike is offline Find More Posts by Dynomike
Reply With Quote
Old Oct 02, 2005, 08:40 PM
Registered User
Joined Aug 2004
986 Posts
It is definitely continuing to vibrate while in flight.
The prop is mounted on what is normally a very quiet/silent outrunner
but with the 9x7.5 it makes a distinctive vibration noise.
I wonder if others have noticed/expierienced this too.
sbmon is offline Find More Posts by sbmon
Reply With Quote
Old Oct 02, 2005, 09:30 PM
Airplane Gearhead
Central N.Y.
Joined Jan 2005
1,132 Posts
I only have 1 of the 9x7.5's and it wasn't badly out of balance.
I did however have a few of the older design 9x6SF's that were real bad...the hole was off center. It obviously was a problem with either the mold, or the manuf. machining set-up for drilling the hole (probably the latter)

IMO the best way to balance these props is spraying the light blade with Krylon "Crystal Clear" in the rattle can...
proptop is offline Find More Posts by proptop
Reply With Quote
Old Oct 03, 2005, 04:38 AM
Registered User
Joined Aug 2004
986 Posts
Thank you
for the information everyone

shawn
sbmon is offline Find More Posts by sbmon
Reply With Quote
Old Oct 03, 2005, 04:57 AM
Registered User
Bill Glover's Avatar
United Kingdom, Bracknell
Joined Nov 2000
11,480 Posts
I also balance every prop. before use, all my APCs (SF and E series) have needed some work. I normally use clear tape on the back face of the 'light' blade, at the tip.
Bill Glover is offline Find More Posts by Bill Glover
Reply With Quote
Old Oct 03, 2005, 08:01 AM
Registered User
Cincinnati
Joined Jul 2004
616 Posts
Possibly while on your balancer, you are piloting the prop off the larger pocket on the back side of the hub (which is typically well-centered) but on the motor shaft you are piloting the prop off the crude through-hole toward the front of the prop which is often way off-center.

Mike H.
Dynomike is offline Find More Posts by Dynomike
Reply With Quote
Old Oct 03, 2005, 08:22 AM
Master of 1 point landing
Naperville, IL
Joined Jul 2005
2,841 Posts
I typically only balance Master Airscrew props, but I only typically use MAS or GWS props. THis weekend, my last 11X7GWS HD prop decided it didnt want to be attached to my plane anymore, and went spinning off into 'never to be found' land. Well, went to my LHS and they didnt have HD props. Purchased two APC-E 11X8 and two 11X8.5. I mounted a 11X8 to the plane, gave her juice, the vibration was terrible (I am using the correct prop adapted so there is no play between prop and shaft adapter).

I took the prop off and put in on my prop balancer. I have NEVER seen a prop so badly out of balance. I put the other 11X8 on, it was a bit better, but still out. I balance one, the other was so bad, I just tossed it out. The 11X8.5's were better, but still not good, I balanced them as well.

Since I never really put a GWS prop on the balancer and I had the balancer out - I did so. I checked about 10 of the GWS props I have ranging from 6-12 ", SF and HD mix. None of the GWS props seemed to be badly out of balance. I didnt do squat with any of them.

Moral of the story - APC props really need to be checked and balanced if needed. I think the larger props (>10") seem to be almost always needing balancing.

B
ImaBiggles is offline Find More Posts by ImaBiggles
Reply With Quote
Old Oct 03, 2005, 08:23 AM
Registered User
Bill Glover's Avatar
United Kingdom, Bracknell
Joined Nov 2000
11,480 Posts
I balance props ready to run i.e. with whatever press-in ring is needed (to fit the motor shaft) already in place. So it's fairly academic whether the problem is caused by one blade being heavier that the other, or the hub being offset!

I'm not singling out APC btw, props from Aeronaut and Graupner almost always need balancing too (the worst being the CAM Speed 5.5x4.3).
Bill Glover is offline Find More Posts by Bill Glover
Reply With Quote
Old Oct 03, 2005, 08:28 AM
Registered User
Bill Glover's Avatar
United Kingdom, Bracknell
Joined Nov 2000
11,480 Posts
Quote:
Originally Posted by ImaBiggles
None of the GWS props seemed to be badly out of balance.
I use GWS HD 8x4 and 9x5 props on my Shockies and they're pretty good, but I still balance them (after reaming the hubs to fit the shaft adapters on my Axi and PJS).
Bill Glover is offline Find More Posts by Bill Glover
Reply With Quote
Old Oct 03, 2005, 10:50 AM
Registered User
Dr Kiwi's Avatar
Chattanooga, Tennessee, United States
Joined May 2003
27,197 Posts
Quote:
Originally Posted by Bill Glover
I'm not singling out APC btw, props from Aeronaut and Graupner almost always need balancing too (the worst being the CAM Speed 5.5x4.3).
The worst one I've had was an Aeronaut 7x7 - that took a heck of a lot of sanding of the back of the heavier blade before it was right! I knew I was going to be getting up to 10,500rpm or so on the Walkera 3200, and I didn't care to have it out of whack!

Cheers, Phil
Dr Kiwi is offline Find More Posts by Dr Kiwi
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Prop issues: APC SF vs. APC C2 Prop taekwondo Electric Plane Talk 4 Aug 25, 2006 02:11 PM
Found WANTED APC E-Series 9x7.5, 10x6, and/or 11x5.5 PROP freedomflyer Aircraft - Electric - Power Systems (FS/W) 3 Jul 02, 2006 03:29 PM
AXI 2808/20 with APC 9x7.5 slowfly prop Firefly_too Power Systems 9 Oct 26, 2005 10:42 PM
Need to select outrunner for 9x7.5 prop SuperHornet Power Systems 16 Sep 17, 2005 12:13 AM
Safe to use APC SF prop on AXI 2808/24 DD? carguy Power Systems 3 Jun 23, 2003 03:41 PM