Folding Blades

[Erfolg]

I have written a similiar thread previously, and received no replies. I am hoping with all the new members, things could well be different.

I have a number of folding propeller assemblies from  J Perkins, which worked well with brushed motors. The brushed motors would push out a breath taking 80 watts when new. How ever I now only use brushedless motors with lipo, typically these will deliver easily + 120 watts and much more.

The blades of the JP will not stand this level of power, having shed 2 seperate blades, destroying the front of the model in both instances. Either as white or black blades.

I have sucessfully used both Graupner and Aeronauht with these hubs. However I am wondering is there an alternative.

Does any one know of an alternative to the above, which will take the stress arising with brushless motors.

Regards

Erfolg

[Alistair Taylor]

Gaupner do make hubs which may be a bit more substantial.

Quite a few distributors offer aluminium hubs for folding props, e.g:

http://www.rcmdirect.co.uk/store/index.php?main_page=index&cPath=121_119

AliT

[Erfolg]

Alistar

It is not the JP hub that is the problem, it is the blades. I have noticed that some Multiplex kits come with plastic hubs. but seem to have better blades than the JP offering (do seem to remain intact).

I use both Graupner and Overlander alluminium hubs, both fine

To be fair to JP, their products are/were targeted at the 480 brushed market not the brushless.

So it is an alternative to Aeronauht/Graupner blades I am seeking, both excellent products.

Erfolg

[Former Member]

[This posting has been removed]

[Erfolg]

I believe you are correct with regard JP. I have used folders (Graupner/Aeronaut/Overlander) at +300w. I have also seen folders by the same people to push out +500w, on other peoples models. They seem to work fine. The problem seem to be that the blades can be the weak link, where a casual examination tells you little. It does seem the label means everyyhing in this instance. Which does get up my nose.

Erfolg

[Alistair Taylor]

It may be that what you need is a blade with a wider root (i.e. the width of the part of the blade through which the bolt passes that attaches it to the hub).

Graupner do a 6x3 with a 6mm root, and a 7x4 with an 8mm root (see Puffin Models stock list)

I'm not sure what size root the JP ones are that you've had disintegrate - but I wouldn't be surprised if they were 4mm - which would (IMHO) be why they can't take 120watts.

You will then need a different spinner.

AlistairT

[Erfolg]

I do use Graupner/Aeronaut at both 6 & 8mm, dependant on the hub.

Perkins are 6mm, they have all broken at the transition from the root to the blade. All the failures had the characteristics of a brittle failure. That is a pitted surface, looking a bit like grains of sand on a flatish surface. The blades appear to be a simple polymer with no re-enforcing fibres (not a composite type material), one claimed to be carbon, but there was no evidence visible to the eye of fibres.

I am looking to an alternative supplier of blades, as I have to send away for them, which is a pain, to either Gliders, West Sussex. They do good prices, it is the postage that is a real nuisance for low value items. I have once gambled on blade size and pitches that i may use, but I then have to remember where I placed them for safe keeping (not my forte).

This forum seems a good place to find out what others do.

Erfolg 

[Alistair Taylor]

Erfolg

You might want to check whether the blades foul the spinner/nosering before they lie flush against the fus. Landing with one blade down that's hard against the spinner backplate or fuselage nosering, but with the prop tip still proud of the fus, will result in a lot of stress being put on the root of the blade - setting up a weak point for later failure if the blade doesn't break immediately.

I managed to bend a 5mm gearbox shaft in just this manner....doh!

Just an idea.

Ali

[Erfolg]

Alistair

You have made a good point. I do not think that the failures I have had can be related to the folding flat issue. The failures have always occured on the same model, within minutes of using the blades for the first time. It is not the most powerful motor either, a 120w motor.

I have had concerns with other models, particularly when having trouble getting the motor brake function to operate (propeller freewheeling).

Ther problem so far only eflicts the JR blades, change the blades to Graupner etc. problem goes away.

APC seem alright at about 100w, but their fixing is by recessed spigots (never gone beyond).

It might be an idea to start rating folder assemblies for duty.

Regards

Erfolg

[Alistair Taylor]

Hmmm - I agree.

I've got a speed 280/300 (brushed) folding prop assembly that I've been thinking of using on a 120W+ inrunner brushless.

Might hang fire on this - or test it in a wide open space free of onlookers...

AlistairT

[Helidel]

Hi Erflog,

I've been using the following, on my Spotfire, for over a 2 years now with no problems

Kontronics geared 205 series ~ 3S 2100 Lipo

Graupner folder 11 x 7 ~ 25A ~ 230W

       "          "      10 x 7 ~ 21A ~ 190W (cam)

I don't use a hub though.

Helidel
 

[Former Member]

[This posting has been removed]

[Erfolg]

You are correct in your assumption that JP hubs/spinners limit the movement past the 90 degrees to the axis of the rotor. Although Aeronaut blades do not break mounted on the same hub/spinner.

Erfolg