Which prop balancer??

[Graham Bowers]

When using my SLEC prop balancer** on an APC 17 x 8 electric prop, the tips of the two cones on the arbor touch each other before the flanks of the cones engage with the hub. A rattling good fit ;-) I improvised by adding a second locating ring that engaged with the hub for about 1  mm of length, but that's not the way forward.

 

What are you users of larger props using to balance them please? 

 

** see attachment

[Geoff S]

Mine's a Du Bro which is similar to the SLEC one but allows bigger props to overhang the bench so, in practice, there's no limit to prop size.

 

[Dickw]

With the SLEC, try turning one of the cones around to form a "flat" for the hub to butt up to and just use the remaining "cone" for centring.

 

Dick

[Graham Bowers]

46 minutes ago, Dickw said:

With the SLEC, try turning one of the cones around to form a "flat" for the hub to butt up to and just use the remaining "cone" for centring.

 

Dick

Thanks for that. I did try it however the prop wasn't securely centred. I'm OK with improvising in principle, provided it's effective. Unfortunately not so in this case.

 

I'm happy enough stumping up for a new balancer, it's just I need some way of evaluating what's out there, and experiences of members here help with that.

[Graham Bowers]

3 hours ago, Geoff S said:

Mine's a Du Bro which is similar to the SLEC one but allows bigger props to overhang the bench so, in practice, there's no limit to prop size.

 

Thanks for that, I rummaged around a bit on line and saw that one.

 

The issue with the one I have isn't prop diameter though, it's the fact that the cones are too small for the prop I'm trying to balance. So the cone tips meet, as is depicted in the photo attached to my original post, before the cone flanks engage with the hub. So the prop isn't supported by the cone flanks.

 

It's hard to form an opinion on how well alternate offerings will perform in that respect, to be honest. I'm sort of hoping this is a known limitation of the SLEC offering, and others have found a solution.

[EarlyBird]

Have you fitted a centring bush for balancing?

 

 

Fit the smallest.

[KenC]

What about this one , under £10 delivered !

[Geoff S]

20 minutes ago, Graham Bowers said:

Thanks for that, I rummaged around a bit on line and saw that one.

 

The issue with the one I have isn't prop diameter though, it's the fact that the cones are too small for the prop I'm trying to balance. So the cone tips meet, as is depicted in the photo attached to my original post, before the cone flanks engage with the hub. So the prop isn't supported by the cone flanks.

 

It's hard to form an opinion on how well alternate offerings will perform in that respect, to be honest. I'm sort of hoping this is a known limitation of the SLEC offering, and others have found a solution.

 

I've never had a problem with any props, electric or otherwise.  Make sure you fit the inserts in electric props or the balance will be off.  The balancer shown above in KenC's post looks very like the DuBro I have and should work the same.  Looks a good price, too.

[Ron Gray]

That’s the same as the Du-Bro one and will result in the same problem. I have found the same issue when trying to balance props reamed out for the Laser tube prop nuts, at 13mm diameter the balancer cones touch before holding the prop. Answer, 3D printed ones (cones).

[Simon Chaddock]

I have a SLEC but also a magnetic bearing balancer.

It

It can only balance props horizontally. Not sure why you would need to do anything else as the bearings are self cantering you can always flip the prop over 180 degrees.

Indeed it is so sensitive it shows the balancer itself is very slightly out of balance!

https://www.youtube.com/watch?v=ev-VooBGCPc 

[SIMON CRAGG]

I also use a magnetic balancer.

 

I have regularly balanced 12 bladed 70mm fans, and found that a standard balancer was much to "course".

 

With the magnetic job, I can get a 12 bladed fan balanced spot on.

 

Good bit of kit.

[Graham Bowers]

6 hours ago, Ron Gray said:

That’s the same as the Du-Bro one and will result in the same problem. I have found the same issue when trying to balance props reamed out for the Laser tube prop nuts, at 13mm diameter the balancer cones touch before holding the prop. Answer, 3D printed ones (cones).

3D printed cones had occurred to me, unless a simpler solution emerged. Better flash up the Prusa 😉

[Mike T]

I use a Du-Bro and the thing from Ali Express is a knock-off.  My largest prop bore is 10mm and I don't think it's ever been a problem.

 

Re magnetic balancers, I came across a cheap little MP Jet 'finger' balancer - a bar with very sharp spikes at each end and 2 friction-fit cones.  You hold the bar (gingerly) between thumb and forefinger to check prop balance.  Having a lot of powerful magnets handy, I bought one to try and make my own magnetic balancer.  Bleddy bar turned out to be stainless...

[Paul De Tourtoulon]

1 hour ago, SIMON CRAGG said:

I also use a magnetic balancer.

 

I have regularly balanced 12 bladed 70mm fans, and found that a standard balancer was much to "course".

 

With the magnetic job, I can get a 12 bladed fan balanced spot on.

 

Good bit of kit.

Have you tried the way Wren kit turbines are balanced,I built and balanced mine and spun it up to 190.000 rpm and the nothing was shaking other than my knees.

[Ron Gray]

10 hours ago, Graham Bowers said:

Unless a simpler solution emerged.

20 minutes from design to finished print (@50% fill), what could be simpler?

[Ron Gray]

[Graham Bowers]

12 hours ago, Ron Gray said:

20 minutes from design to finished print (@50% fill), what could be simpler?

They look very purposeful 😉

 

 

 

[Graham Bowers]

Many thanks for all responses.

 

Short term I'll try fitting the smallest centering bush - can't believe I didn't think of that! The hub is very shallow however that may give me enough.

 

Failing that, I'll knock up some 3D printed cones.

 

Depending on how that goes, perhaps another balancer; seems magnetic offer the best performance.

[Graham Bowers]

Just closing the loop on this one.

 

Using the smallest centering bush wasn't enough, so I went with the 3D printer.

 

I only needed one obtuse cone, I went with 90 degrees.

 

If I'd balanced before drilling out to 8mm, the smallest centering bush would have worked, as I discovered when I balanced the spare (undrilled) prop.

 

 

[Dickw]

There is always a way for the determined 👍

 

Dick

 

[aidan mcatamney]

I'm still using my Slec Balancer since I bought it in the local model shop back in 1995.   Great little article it is.  

[Ron Gray]

19 minutes ago, Graham Bowers said:

If I'd balanced before drilling out to 8mm

Ah but then you wouldn’t be balancing the finished prop!

[Graham Bowers]

35 minutes ago, Ron Gray said:

Ah but then you wouldn’t be balancing the finished prop!

That's very true!

 

Possibly a future experiment to see if the process is capable of detecting the potential out of balance force caused by removing around 0.00007 grammes of material at the bore of the hub ;-)

 

6.3mm hole drilled to 8mm. Thickness of the hub at that point is 2.5mm. Electronic caliper measurements. Not sure what APC props are made of, so assumed 1.5 g/cm3

 

Think my sums are right.............................

[Graham Bowers]

1 hour ago, Dickw said:

There is always a way for the determined 👍

Dick

That's nice, some call me stubborn ;-)