Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

Proper Balance

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Old 02-05-2009, 08:17 PM
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asmithnc
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Default Proper Balance

Just recieved my first Jett engine and would like some tips on fine tuning props. Since I am stepping up from OS..... and now spinning higher rpm's I want to be safe. Planning on using APC 10 x 6. Looking for the best ways to balance props. Thanks Andy
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Old 02-05-2009, 08:34 PM
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which jett is this? that would be a start.[X(]
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Old 02-05-2009, 08:46 PM
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60LX
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Old 02-05-2009, 09:53 PM
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nice!! too many people are more experienced than me in this area. but i have a couple of k & b's i want to run and make noise with. i will watch this thread myself. thx
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Old 02-05-2009, 09:56 PM
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Default RE: Proper Balance

hi,

I would try the Jett support forum here on RCU... or their website FAQ's... just for starters.. after all its their engine and they do KNOW the biz and can help.. just my 02cents.

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Old 02-05-2009, 09:59 PM
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Default RE: Proper Balance

oh

I'll also keep tabs on this thread as that is the engine I want on my SD 50... love it.. if even half of the reports I have read are accurate you will be very impressed with your purchase..

I have their jettstream pipe and it is amazing, not only looks great but really wakes up the OS


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Old 02-06-2009, 07:36 AM
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Default RE: Proper Balance

I've used this one for several years and like it. http://www3.towerhobbies.com/cgi-bin...&I=LXD712&P=ML
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Old 02-06-2009, 08:40 AM
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Default RE: Proper Balance

i havc use the top flite balancer for years...

http://www3.towerhobbies.com/cgi-bin...&I=LXHY61&P=ML
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Old 02-07-2009, 02:02 AM
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Default RE: Proper Balance

I've used the fingertip type and found they are very good with practice.
http://www3.towerhobbies.com/cgi-bin...?&I=LXK247&P=7

The picture in the ad is incorrect, the hand should be positioned below with the shaft points resting on the fingers, not squeezing.
I use a small smooth file on the on the last third of the front side of the heavy blade and when it gets close I sand it smooth with 400 grit sand paper. Maintain the original airfoil and don’t nick or gouge with the file. Take your time and check frequently, this is fast with the finger tip type as you can leave it on as you work on it.
On wood props I round the leading edge, one coat of fuel proof paint on the entire prop than add coats to the light blade, re check balance after the paint is dried.


I have both the Dubro and the Top Flight Power point balancers as well. My Dubro is subject to dust problems and the cones on my Power Point don't center well. The finger tip type is very portable and so cheap I keep a few to give to newbies to balance those forgiving but many times out of balance Master Airscrew G/F series props that are found on trainers.

Lately all models of fresh stock Master Airscrew props have been excellent in balance. The APC have always been very good in balance, so good I often no longer check in the popular 11”, 10" and 9" sizes. On the APC the most common reason for imbalance is the hole was not punched out in center of the rear counter bore and that’s been a while since I've seen one like that. The rear counter bore is the true center of the prop and this is good to know if you are reaming out the hole for a larger shaft.

With all balancers, you can’t have any wind when you do it. At the field, I get in my car to balance.
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Old 02-07-2009, 02:15 AM
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Default RE: Proper Balance

ORIGINAL: freakingfast

Lately all models of fresh stock Master Airscrew props have been excellent in balance. The APC have always been very good in balance, so good I often no longer check in the popular 11”, 10" and 9" sizes. On the APC the most common reason for imbalance is the hole was not punched out in center of the rear counter bore and that’s been a while since I've seen one like that. The rear counter bore is the true center of the prop and this is good to know if you are reaming out the hole for a larger shaft.

With all balancers, you can’t have any wind when you do it. At the field, I get in my car to balance.
And no wind in the car either.. field grub or not. Rising air will lift the closest blade.

The hole in the back of the APC prop hubs is indeed dead-nuts on center, because it is molded in place. The through hole is post drilled. They may have cleaned up their act with the drilling fixtures, because like you observed there seem to be less wacko holes these days. But there are still a few. Over-drilled hubs and bushings in the rear hole are the ideal way to get them centered, but that is a little too much piddling around for most folks. Lathe owners or people with access to one are a different story.

Oh yeah, I have one of the magnetic balancers, what brand are they, GP? I'm spoiled by it's accuracy and free movement, and use nothing else if possible anymore. You gotta get the points ground dead center on the axle though.

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Old 02-07-2009, 07:37 AM
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Speaking of reaming the hole. . .

Perhaps this is too anal, what ever. I don't care much for hand reamers. they just seem cheap to me. I have a machine shop so a chucking reamer just makes more sense. With a drill press, you can get identical results. I use reamers bought through industrial supply catalogs. A HSS reamer is all you need and it should run around 300-500 rpm (no more) Clamp your work piece down (vice) and ensure your work surface is perpendicular to the drill chuck/quill centerline. There's a couple ways of doing this and if anyone is interested, just ask and I'll be more than happy to walk you through it. Works on milling machines too. (what it's actually meant for really)

It's a bit more work, but the surface finishes are better and the reamer will put the hole on size and this means less runout at the prop tips when the thing is actually on the engine running. Also means the hole is square and that will result in longer bearing life and a prop that doesn't have an "overbite." (running out of square in relation to crank centerline)

If your doing a wood prop or using a drill adapter like for a DA, use a wood backer and it won't blast out the wood on the back side when the drill goes through. A dab of CA to glue the drill guide to the prop during drilling sure helps too. then just a whack with a mallet and it comes free. Scrape off the CA and your done. Works great.

Good luck.

C
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Old 02-07-2009, 08:46 AM
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Default RE: Proper Balance

Thanks guys for your response. I have the Top Flite balancer. Now how do you guys correctly fine tune your prop for balance. I have sanded / drilled holes etc. With this engine higher rpm's I would like to stay safe. I would not like to see my prop fall apart while bench testing.
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Old 02-07-2009, 10:49 AM
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See post #9
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Old 02-07-2009, 12:47 PM
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ORIGINAL: nesikachad

Speaking of reaming the hole. . .

Perhaps this is too anal, what ever. I don't care much for hand reamers. they just seem cheap to me. I have a machine shop so a chucking reamer just makes more sense. With a drill press, you can get identical results. I use reamers bought through industrial supply catalogs. A HSS reamer is all you need and it should run around 300-500 rpm (no more) Clamp your work piece down (vice) and ensure your work surface is perpendicular to the drill chuck/quill centerline. There's a couple ways of doing this and if anyone is interested, just ask and I'll be more than happy to walk you through it. Works on milling machines too. (what it's actually meant for really)

It's a bit more work, but the surface finishes are better and the reamer will put the hole on size and this means less runout at the prop tips when the thing is actually on the engine running. Also means the hole is square and that will result in longer bearing life and a prop that doesn't have an "overbite." (running out of square in relation to crank centerline)

Good luck.

C
http://masterairscrew.com/images/dri...structions.pdf

If you ream out props time to time, this is a cool little tool but you need a drill press.
Just make sure it can’t spin and get ya if it grabs, two stop pins, (one on each blade) or do it in the bottom of a machine vice. THINK!


I use the hand reamers all the time. The hole position will be no better than the existing pilot hole with the potential to make it a lot worse. I have found that it centers much better if you hold the tool still and turn the prop, this way you are less likely to force it to one side. I keep these in my field box too and they get barrowed at least twice a year.
It’s a good idea to balance after reaming the hole.

I did take some carbon fiber props to work and made a fixture to hold them while I used a real .377” reamer that piloted from the back 3/8” counter bore. This let the prop shaft adaptor fit.

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