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I'm about to fit my new BM on my Jab 2.2. It has been drilled with quite large holes, presumably to fit over the prop drive lugs.

 

Based on discussions on this thread I plan to mount it in front of the prop, where the 1/4" bolts poke out. I plan to fill these large holes with thin washers to accurately centre the plate. Anyone see a problem?

 

 

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I'm about to fit my new BM on my Jab 2.2. It has been drilled with quite large holes, presumably to fit over the prop drive lugs.

Based on discussions on this thread I plan to mount it in front of the prop, where the 1/4" bolts poke out. I plan to fill these large holes with thin washers to accurately centre the plate. Anyone see a problem?

I am sure there will be other better informed responses than mine but for what its worth - I would avoid adding any additional washers/weights.  If you have purchased the correct BM for your application it should be a snug centred fit without having to add spacers of any sort. Check you have the correct BM. If I remember correctly, you can even purchase a BM without holes (to drill yourself) for those few applications where there is no suitable factory model.

 

 

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The only problem that I can see is, acquiring washers with the correct OD and ID to ensure they're a snug fit. Any gaps would allow movement to start. I'd machine up some solid bushings to ensure the fit is precise, as regards OD and ID.

 

 

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... If you have purchased the correct BM for your application it should be a snug centred fit without having to add spacers of any sort...

I asked for it to be drilled for my prop, but it never occurred to me that I'd need to mention I wanted to mount it in front of the prop.

 

The only problem that I can see is, acquiring washers with the correct OD and ID to ensure they're a snug fit. Any gaps would allow movement to start. I'd machine up some solid bushings to ensure the fit is precise, as regards OD and ID.

Good point, OT. That's what I plan to do, because I'd be lucky to find washers of the same thickness, let alone size.

 

I presume there's no reason I can't use aluminium sheet if I can find one the same thickness as my BM plate. 

 

 

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you only need a centring bush/washer...it doesnt need to be exactly the same thickness it could be thinner than the base metal plate. The washers on the bolt heads do the work of holding the plate and prop on

 

 

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you only need a centring bush/washer...it doesnt need to be exactly the same thickness it could be thinner than the base metal plate. The washers on the bolt heads do the work of holding the plate and prop on

In my Jab installation, an alloy crush plate fits in front of the prop; Belleville washers and a nylok nut fit over each bolt, 

 

If I put the BM between the crush plate and the prop, I need 6 well-fitting washers to centre it.

 

If I fit the BM outboard of the crush plate, I'd need wider washers over it and under the Belleville washers, leaving me precious  few threads past the nylok nut.

 

Which is better?

 

 

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I wouldnt be mounting the BM over the top of the belville washers. that could twist the BM a little if it wasnt perfect. Backing the BM onto a flat surface would be far better I would think. That way you just need centreing ring/washers in the holes in the BM

 

 

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I wouldnt be mounting the BM over the top of the belville washers. that could twist the BM a little if it wasnt perfect. Backing the BM onto a flat surface would be far better I would think. That way you just need centreing ring/washers in the holes in the BM

Thanks Mark, but that was never my intention. I want it against the front of the prop. My problem is how to ensure its well centred.

 

 

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maybe you need to find the hole size in the BM and get some alu or steel or brass tube the right size then cut off some thin slices..its only for centreing...not sure how many bolts are there but you wouldnt need them all..just 4 opposites or 3 in 120deg if its 6 bolts

 

 

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Old K ,  will you have an actual measurement of vibration before and after fitting the BM? I've thought about fitting a vibration sender, they are quite cheap and available eg from hobbyking. 

 

When I do have a meter installed, I will be keen to try a BM. Until then, my sense of vibration is not reliable enough to really know if an improvement has been achieved. 

 

 

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Old K ,  will you have an actual measurement of vibration before and after fitting the BM? I've thought about fitting a vibration sender, they are quite cheap and available eg from hobbyking. 

When I do have a meter installed, I will be keen to try a BM. Until then, my sense of vibration is not reliable enough to really know if an improvement has been achieved. 

No Bruce, I don't have any sort of vibe measuring instrument; I'm happy to rely on the difference in feel and sound.

 

The newest to an objective measurement I'll have is my paper flight plans which I fill in as the engine is warming up. Going back thru a decade of them shows a noticeable change in the my writing- or maybe it's just Parkinson's...

 

 

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Over 40+ years, I've owned four. Did they work? No. I wish I had learned from my mistake of 35 years ago.

Interesting, Callahan. I've also heard that from a mate who has a lifetime of experience with aeroplanes.

 

He offered me his old balance ring, but it's filled with ball bearings, not mercury.

 

 

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The 912 balancer makes a noticeable difference to smooth running. After fitting the balancer you will be able to lower the idle considerably without the engine become rough and stopping.

 

The best I have seen is still running at 650 rpm which is well below normal shutdown.

 

 

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Did you get your BM from Danny?....He will swap it for a blank one you can drill if you want. The holes are drilled for the studs that come off the prop flange. Contact him if you did. I was speaking to him tonight about it

 

 

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Over 40+ years, I've owned four. Did they work? No. I wish I had learned from my mistake of 35 years ago.

Interesting...I was skeptical when I put one on my Drifter, but was pleasantly surprised. Huge difference throughout the rev range and no more numb feet.

 

Also, they can only compensate for a certain amount, if you have a serious issue, it's not going to magically fix it.

 

Did you ever sort out the vibes on your Drifter?

 

 

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Did you get your BM from Danny?....He will swap it for a blank one you can drill if you want. The holes are drilled for the studs that come off the prop flange. Contact him if you did. I was speaking to him tonight about it

Sure did, Mark. I don't want to bother him any further, especially after my bank fouled up a money transfer.

 

It would be quicker to make up six washers to centre it.

 

Can you do a re drill between you large holes that way you can fit where ever you want.

Good idea, BA, but doing that accurately is beyond my equipment and skill.

 

 

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  • 3 weeks later...

I have a question, but Not on the "Balancemaster.

 

I know sitting in a "Tractor aircraft you face the prop & say it's, either "clock or anticlock-wise rotation.

 

BUT

 

In a Pusher, do you rotate your Head 180 degrees, or Stand behind prop To say which is the rotation, ( left, or Right handed prop).

 

Reason, My Rotax 582, (cheapie motor) seems to have a tractor prop on backwards, was offered a replacement, but it also looks like a tractor prop.

 

AND

 

The 1/2 VW motors are the worst for vibration, Iv,e ever encountered, No talk of a "B M" on those engines:, re. the mercury thing, in a rotating ring, wouldn't the mercury get pushed to the furthest point of the circumference.( opposite of aim).

 

spacesailor

 

 

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The balancer will displace the mercury to the opposite point to balance out the imperfection

 

no Balancers for VW. Bolly would supply a suitable pusher prop. The Rotax 582 is clockwise rotation as you stand behind it.

 

 

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I have a question, but Not on the "Balancemaster.

I know sitting in a "Tractor aircraft you face the prop & say it's, either "clock or anticlock-wise rotation.

 

BUT

 

In a Pusher, do you rotate your Head 180 degrees, or Stand behind prop To say which is the rotation, ( left, or Right handed prop).

 

Reason, My Rotax 582, (cheapie motor) seems to have a tractor prop on backwards, was offered a replacement, but it also looks like a tractor prop.

 

AND

 

The 1/2 VW motors are the worst for vibration, Iv,e ever encountered, No talk of a "B M" on those engines:, re. the mercury thing, in a rotating ring, wouldn't the mercury get pushed to the furthest point of the circumference.( opposite of aim).

 

spacesailor

Always as if you are standing behind the aircraft. CW is RH ...CCW is LH.

 

A LH or CCW prop will always be a LH or CCW prop, yes, you could put it on backwards, but all that will do is make it turn with the trailing edge first.....not very efficient, and it will still push the same way.

 

 

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Will putting extra "pitch" on a trailing edge first prop, make up for it's over revving of the motor.

 

silly question but I presume it would be under-pitched running in reverse.

 

spacesailor

 

 

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