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Can I balance my own prop?


stuartasutherland
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Hi, having only 4 solo flights under my belt I'm learning a lot each time I go up. I've suffered a bit from vibration and on a post flight inspection tonight discovered I've broken my muffler strap.

I fly a Parajet Macro with a Born wooden prop. (I broke the lovely Pulse prop I got with it - sorry Pete)

It doesn't seem too bad until I pull the power, then it becomes uncomfortable. Romania is a long way to send it back to!

So can I balance my own prop with some home made kit?

Is there a kit I can buy to help me?

Many thanks for any advice - cant wait to get up again!

Stuart :wingover:

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Hi Stuart, yes you can but I would be tempted to leave it to someone more experienced, I needed two props balanced a couple of years ago and went over to my local microlight airfield to ask around, I was soon pointed to a nice chap who took my props and balanced both perfectly, and all for only twenty of my english pounds. :D

mite be worth a try :D

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Hi, having only 4 solo flights under my belt I'm learning a lot each time I go up. I've suffered a bit from vibration and on a post flight inspection tonight discovered I've broken my muffler strap.

I fly a Parajet Macro with a Born wooden prop. (I broke the lovely Pulse prop I got with it - sorry Pete)

It doesn't seem too bad until I pull the power, then it becomes uncomfortable. Romania is a long way to send it back to!

So can I balance my own prop with some home made kit?

Is there a kit I can buy to help me?

Many thanks for any advice - cant wait to get up again!

Stuart :wingover:

Well thats what you get for not buying british :lol:

Yes I know Im not producing yet due to unforeseen work that has to be done, but I will get back to it ASAP.

I can still repair or/and balance your prop.

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Pete, thanks for the offer. I'll take you up on it if I get nowhere with my local microlight community.

I did come to you first for a new prop! :D

Can you let me know an approximate cost please. PM if you prefer.

Thanks

Stuart

If the finish on the prop now is good then it would be about £25 +p&p

If the finish is not good then it would be about £60-£80.

I only send it back out when I am happy with the finish.

I have a polini prop here that I have repaired and

they must finish them with a chisel and oily stain it is a really rough finish and the

Lacquer will not take to it.

It will be finished this week some time :D

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I've just sent one back to Romania for balancing, although I doubt that it is possible as it was out of balance by an extreme amount in the chord direction. I needed to place 6 x £1.00 coins (60g) 30mm from centre to get it to balance. As it's across the chord, it is hard to see how you could place enough lead at the hub! My motor was also shaking itself to bits.

I suggest you use a simple means to check balance (lawn mower cone type balancer, or preferably the pivot point adjustable hang type) to see if it is out an extreme amount. If it is, and it's relatively new, then contact the maker. If it is out by a small amount then the spray laquer and/or material removal tricks should suffice, or for piece of mind get someone to do it. I wouldn't put a new prop on without checking balance again.

I'd be interested to learn if yours is similar to mine.

For information, the cost of sending to Romania was £35 with Parcelforce.

Steve

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Okay, so being Scottish I thought I'd have a wee go myself at balancing my prop. Born Props said to sent it back if I want to be checked but its quite expensive postage.

I scoured the interweb and made the device below. Tried it out on all axis, and they all fell on the same side of the prop. Great - that takes out any doubt the one side is a bit heavier. I tried the light spray with car laquer technique until it was totally balanced.

I tried also the other prop I had sent over at the same time (I may be Scottish but I'm not stupid!). It seemed fine.

I went out tonight with high hopes of a smooth flight but I still seemed to get vibration, quite high frequency and not that comfortable at the higher revs. I did a quick circuit and landed to change over to the new prop.

Took off and it too gave the same problem.

So, am I missing something? Can it be something other than the prop? The bearing where the prop mounts on to seems good.

Thanks for your help.

Stuart

5733640befda8_photo(3).JPG.963a9b90c02c9

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Are you sure that it is balanced across the chord (90°) to the spanwise balance. I don't see how your balance jig can check for that properly unless the prop is free to turn through 360°. Check that everything else is secure on the motor/frame. After running an out of balance prop, I found that my exhaust downpipe was loose and resonating, even when running a balanced prop afterwards. I took it off, cleaned up the joints and copperslipped them and it is a lot quieter. Steve

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Vibration can be generated through a misaligned engine pulley as well.

Yes, they're usually conical, self aligning, but install them a bit too loose and ptoing they go just a little cockeyed.

That or a spec of dirt under pulley.

If you can check runout on it while slowly turning prop by hand, it may be the source of your remaining hi rpm vibes.

This shows up in flight as a cyclic (wumwumwum) harmonic with engine speed as the pulley loads and unloads the belt.

Quite often only those on the ground pick up on it as pilot is overcome by wind and prop noises.

It will kill your main bearings eventually and wear your belt sooner. It may kill feeling in fleshy bits temporarily...

Find yourself tightening drive belt more often then you think you should?

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I have used one of these balancers in the past, does the job quite nicely and only a few quid.

propeller%20balance%2001.jpg

I bought one and once I'd added some laquer on one side it seemed balanced, thats why I'm worried it isn't the prop.

Dont know where to start if the props come back fine. The belt seems aligned to me, and the hub that the prop screws to seems okay - no play when spun by hand (when the drive belt is off).

Stuart

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I have used one of these balancers in the past, does the job quite nicely and only a few quid.

propeller%20balance%2001.jpg

I bought one and once I'd added some laquer on one side it seemed balanced, thats why I'm worried it isn't the prop.

Dont know where to start if the props come back fine. The belt seems aligned to me, and the hub that the prop screws to seems okay - no play when spun by hand (when the drive belt is off).

Stuart

I have one of these, but I'm a little unsure of it's limitations. I've managaed to balance the prop using spray paint and I made sure by using a tiny spirit level in the centre. No problem. Then, I turned the spirit level 90 degrees and it was way out. Does this mean that the prop is unbalanced in it's chord, or is this device not suitable for measuring this sort of balance?

If it is out, how do I balance it?

I wish Pete B lived around the corner so I could whizz it in :(

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I certainly dont live round the corner from Pete B, but hopefully my sorted props are enroute as the weather up here is good. My props looked balanced on the mower device but one was 10 grams out on the chord, so not fool proof.

Stuart

Posted this morning Sir :D

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I have used one of these balancers in the past, does the job quite nicely and only a few quid.

propeller%20balance%2001.jpg

I bought one and once I'd added some laquer on one side it seemed balanced, thats why I'm worried it isn't the prop.

Dont know where to start if the props come back fine. The belt seems aligned to me, and the hub that the prop screws to seems okay - no play when spun by hand (when the drive belt is off).

Stuart

I have one of these, but I'm a little unsure of it's limitations. I've managaed to balance the prop using spray paint and I made sure by using a tiny spirit level in the centre. No problem. Then, I turned the spirit level 90 degrees and it was way out. Does this mean that the prop is unbalanced in it's chord, or is this device not suitable for measuring this sort of balance?

If it is out, how do I balance it?

I wish Pete B lived around the corner so I could whizz it in :(

One prop insured for £200 sent 48 hours parcel force (from the post office =£12.45

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The problem with the lawn mower balancer (Cone) is that they do not always sit perfectly centered in the hole. If the centre of the cone is even 0.2mm off centre then it will wreck reading. I use it in conjunction with a vernier caliper to ensure the cone is centered. 10g off balance in the chord direction is not that much due to the short distance from the hub centre. I've just had mine "rebalanced" in Romania. It went out with 60g x 30mm off balance and came back with still 40g x 30mm off balance (Chord direction).

They tried to tell be that it was in spec. as even general aviation props are only balanced to 2g x 1m. (It is the product of the distance and weight that is key) I don't believe it!

I'm now going to drill 2 x 1/2" holes in the hub and fill with lead. I've also ordered the hang type balancer.

Prop pitch and balance is a nightmare!

Steve

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The problem with the lawn mower balancer (Cone) is that they do not always sit perfectly centered in the hole. If the centre of the cone is even 0.2mm off centre then it will wreck reading. I use it in conjunction with a vernier caliper to ensure the cone is centered. 10g off balance in the chord direction is not that much due to the short distance from the hub centre. I've just had mine "rebalanced" in Romania. It went out with 60g x 30mm off balance and came back with still 40g x 30mm off balance (Chord direction).

They tried to tell be that it was in spec. as even general aviation props are only balanced to 2g x 1m. (It is the product of the distance and weight that is key) I don't believe it!

I'm now going to drill 2 x 1/2" holes in the hub and fill with lead. I've also ordered the hang type balancer.

Prop pitch and balance is a nightmare!

Steve

Balance is easy when you have the right kit, made mine as there was nothing out there good enough.

Pitch yea that can be a nightmare

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