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Making an electric glider's propeller fold more positively


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Really enjoying my Staufenbiel Vegas glider at the moment - but for small niggle.

Despite quite fierce ESC braking, the 14 inch prop does not readily fold. I often have to pull a big half loop to get it to fold, or practically stall it into wind, which slows the model and hence the prop, until it folds.

Any ideas? I don't want to go down the route of trying to use small rubber bands around the hub and spinner. It's not a big problem and I'm sure I can live with it.

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It's difficult to imagine why, unless there is excessive stiffness in the pivots, which should allow free movement. A stopped prop (I'm assuming it does actually stop?) presents quite a side area to the airflow and should fold with alacrity - the large props on a friend's F5b model make a very audible slap when they fold.

Edit - just saw your subtitle...your braking doesn't seem to be working!  What ESC are you using?  I had trouble with a YEP one (YGE clone) which wouldn't stop the prop using the normal programming card method - but I'm struggling to recall the solution!

Edited By Martin Harris on 31/05/2019 11:12:46

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I sympathise with your plight 'Filmbuff'.

Down the years I've tried various permutations. 'Aeronaut' & similar quality 'folding prop' hubs, bolts & spinner are usually pretty reliable for folding.

If the hub bolt is too free, the prop blade sometimes flops down during slower phases of flight. You say you would prefer not to go down the rubber band route, which is a rough 'n ready fix that generally works. You could try another hub/pivot bolt assembly but the quality ones are usually not cheap. Try 'Gliders' in the UK for their stock or 'Hollein Modelbau' & 'Lindinger Modelbau' in Germany. The latter two give superb service and are very often cheaper than UK even after p&p has been factored in.

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Thanks for the replies guys. The prob hub pivot with the blades is very free.

When on the ground - the ESC brake does appear to work okay. It stops the motor well. In the air, it seems the big prop still has the latent power to rotate the motor.

Using a Dymond 60A ESC.

Reading some forums - they suggest extending the end rate on low throttle - I'll give that a try.

 

Edited By FilmBuff on 31/05/2019 11:41:13

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Posted by Piers Bowlan on 31/05/2019 16:40:50:

Trying another 60A ESC if you have one, is where I would start. If it really is working on the ground, it should stop the prop windmilling in the air. Do you have a programming card for the Dymond ESC? Use that to check that 'Brake on' really is selected. Good luck.

Yes Piers, I have used a programming card - but no harm in checking again!

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Posted by FilmBuff on 31/05/2019 11:34:56:

Thanks for the replies guys. The prob hub pivot with the blades is very free.

When on the ground - the ESC brake does appear to work okay. It stops the motor well. In the air, it seems the big prop still has the latent power to rotate the motor.

Using a Dymond 60A ESC.

Reading some forums - they suggest extending the end rate on low throttle - I'll give that a try.

Edited By FilmBuff on 31/05/2019 11:41:13

The brake function is "dynamic", it's strongest function is from full throttle closed quickly to zero.
Restrain the model safely, apply full throttle for a couple of secs then cut power. If the prop continues freewheeling then the brake is simply not programmed "on".

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@JulianJ that looks interesting - I'll investigate

Took the Vegas out again this morning. On the ground, motor does brake and the blades fold okay.

In flight, I can hear the motor braking, but the large prop still freewheels say 50% of the time.

I can live with it by climbing vertically, slamming the throttle shut and the plane does a flop over loop which always seems to folds the prop. It's then in a good position to start the dive towards earth that provides energy for fun and games aeros with the speed.

Maybe the Dymond ESC is just not providing enough brake.

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Posted by Martin Harris on 02/06/2019 11:11:03:

Do you have a programming card or are you setting by the beep method? I think there's a possibility that some Dymond ESCs only provide braking off/medium by the latter and you need a programing card to set hard braking.

Hi Martin - I have a card and I will double check.

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FilmBuff

I know this is not a folding prop but does your motor brake do something like this. It should be pretty violent from full power.

You should also be able to feel the motor resistance even rotating it by hand (watch you fingers!) with the battery connected and the brake on compared to when the battery is disconnected.

.

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Posted by Koen Smits on 02/06/2019 18:29:02:

@ FilmBuff,

Hello, please look at this link

**LINK**

They have spinners, centerpieces and rubber rings for foldingprops.

the site is in german and englisch.

Good spot. They are on holiday until 4th July. Postage for 6 euros of rubber is 12 euros. Ouch!

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I have found that on some ESC's the brake function doesn't work unless you have the throttle trim on the Tx reduced to almost nothing.

I suspect that with the throttle trim 'centred' (which is the normal default setting) the ESC will assume that the throttle is still slightly open (even though the motor isn't actually turning) and, therefore, will not engage the brake function.

YEP speed controllers seem more likely to exhibit this issue but I am pretty sure the same principle will apply to other makes. This fix has cured an apparently non-operative brake on three of my models (two gliders and one flying wing).

Certainly worth a try...……...takes a few seconds and costs nothing!

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Posted by John Roberts 9 on 05/06/2019 11:44:08:

I have found that on some ESC's the brake function doesn't work unless you have the throttle trim on the Tx reduced to almost nothing.

I suspect that with the throttle trim 'centred' (which is the normal default setting) the ESC will assume that the throttle is still slightly open (even though the motor isn't actually turning) and, therefore, will not engage the brake function.

YEP speed controllers seem more likely to exhibit this issue but I am pretty sure the same principle will apply to other makes. This fix has cured an apparently non-operative brake on three of my models (two gliders and one flying wing).

Certainly worth a try...……...takes a few seconds and costs nothing!

John, when you say throttle trim reduced to nothing - do you mean pulled all the way back? ie use the maximum allowable trim?

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I should add that having done this the brake engaged very positively indeed as soon as I closed the throttle stick......it was immediately obvious that it was working properly.

As I recall, on at least one of the models, I found that the throttle trim didn't need to be completely backed off to nothing for this to work. With a bit of trial & error I found a trim setting that was somewhere between the default mid point and the minimum which was enough to get the brake function working as intended. Probably just down to a slight variation between the ESC's because the Tx (Spektrum DX8) was the same for all the models concerned.

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