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carbon cub , slower after a crash ?


Upkeep
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I had a prang the other day where the battery fell out during a loop, detached from the connector and the cub hit the deck nose first shortly after the battery.

There wasnt much damage to fix but now although the plane is flying great, it seems to be slower than before.

 

Same batteries, same charge etc etc. I wonder if the nose dive in to the field has damaged the motor ? Is that possible ? 

The motor spools up fine, isnt binding or making any strange noises.

 

Or maybe Ive missed something else ? 

 

Ta 

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I have never ever seen a fuel tank depart from an aircraft, model or otherwise, full or empty.

 

Perhaps the fuel pipes help to hold it in place.

 

This seems to happen quite a bit with electric powered ones as mentioned on this forum.

 

A re think needed I suppose...?

 

How many rubber bands hold your wing on I wonder ?

Edited by Rich Griff
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More than likely you damaged the two bearings when you hit the ground. They could be "dragging" and causing loss of top end. They are very small and easily damaged by any undue pressure. Easy to change, available from your nearest motor factor. Try and purchase a known brand, as some of the cheap versions are made of porridge!. Make sure the prop and spinner are running true and balanced ok.

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15 hours ago, Rich Griff said:

I have never ever seen a fuel tank depart from an aircraft, model or otherwise, full or empty.

 

Perhaps the fuel pipes help to hold it in place.

 

This seems to happen quite a bit with electric powered ones as mentioned on this forum.

 

A re think needed I suppose...?

 

How many rubber bands hold your wing on I wonder ?

The reason why batteries are ejected from models when they crash is because they have to be easily removable. This is done either manually at the end of each flight or automatically when the model hits something immovable.

From memory, fuel tank installation is usually done in a manner which means that removal is anticipated to be a rare event and so they are more securely installed.

Also, from the moment you start the engine the mass of the fuel tank starts to decrease which means that towards the end of the flight there is less energy available for ejection.  If the mass of my battery decreases during a flight it means that the battery is on fire and battery ejection is probably the least of my worries!

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1 hour ago, Rich Griff said:

My mistake, I though the chap said the battery came out of the plane when it was doing a loop.

 

He didn't say inside or outside loop, just that it fell out whilst doing a loop, disconnected it's self and landed before the plane did ?

 

A re think needed I feel...

You are right, just read the OP post, fell out in a loop. The battery in the Carbon Cub is underneath and held in (or not) by a velcro strap and the hatch/catch. Looks like the battery was badly secured. As I said, they have to be easily removable, preferably not that easily though

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I would make a strong enough box or shelf that the battery slides into/sits on horizontally and "locked" in place by some white foam, that is locked in place by the hatch.

 

Nice and secure and in place so it don't move, at all.

 

That way the fuz is beefed up a bit and the battery locked in place securely but still easily removable/accessable.

 

The hatch just holds the white foam and it's self in place.

 

Not sure how much room there is to play with in "his" model, maybe since he won't be outside looping a cub, a slight re design needed as to battery position and access ?

 

Velcro strap failures/insufficiencies have been reported before on here....

 

A re think needed chaps....but what do I know, I'm not electric powered...yet !

Edited by Rich Griff
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11 minutes ago, Rich Griff said:

.................................................

 

Velcro strap failures/insufficiencies have been reported before on here....

 

A re think needed chaps....but what do I know, I'm not electric powered...yet !

780 gm 6s battery held in with velcro straps in a very aerobatic plane - - 300+ flights = over 50 hours actually in the air with zero problems.

It is not rocket science - but the velcro does itself have to be properly fixed to something substantial.

 

Dick

 

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Hi dickw,

 

Could you post some pictures of your velcro battery holding please...

 

You say a very aerobatics/acrobatic plane but I bet gravity helps hold the battery in place in an inside loop ?

 

And the velcro etc. Holds the battery in place on an outside loop ?

 

I'm still learning/relearning after a 25 year break, and not into "electric power" yet, but willing and open to learning...

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The battery sits on a ply plate which is part of the structure. The velcro goes through slots in the ply and wraps around the battery. For a battery of that weight I use two straps, one round the middle of the battery and one fore/aft around the length. No velcro on the battery - hot batteries can soften the adhesive!

 

Yes, gravity helps on inside loops, but the velcro holds it on outside loops, knife edge, inverted, and just generally throwing it about. 

 

Just going flying so may take a photo then, but honestly it's not that complicated.

 

Dick

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2 hours ago, Rich Griff said:

I would make a strong enough box or shelf that the battery slides into/sits on horizontally and "locked" in place by some white foam, that is locked in place by the hatch.

 

Nice and secure and in place so it don't move, at all.

 

That way the fuz is beefed up a bit and the battery locked in place securely but still easily removable/accessable.

 

The hatch just holds the white foam and it's self in place....

 

...Velcro strap failures/insufficiencies have been reported before on here....

 

A re think needed chaps....but what do I know, I'm not electric powered...yet !

 

This may work in a conservatively specced powertrain, but for anything with more performance the problem with this idea is ventilation.

 

There is a very good reason velcro is commonly used - if done correctly it allows a firm fixing whilst still allowing plenty of air to flow around the pack on all sides. "Boxing up" your pack in wood and foam is not a good idea because a) it's going to get hotter, shortening cycle life over time, and b) if it starts to swell for any reason (more likely if it's running hotter) you could have a serious problem getting it out, and/or it could cause an internal structural failure. Indeed using your method in the smaller all foam sport models that are so popular now (Timber, Tundra, HH Cub etc) could be a real problem over time as they tend to have very little ventilation to start with.

 

Another point is that often people use different configurations of packs in the same model. Ffor instance in my 6S Sebart Miss Wind I have some 6S packs, but also use 2x 3S packs connected in series on occasion. Velcro and a few carefully selected bits of foam packing that don't interrupt the airflow can always accomodate that, but a battery tomb ? could not. I've never had a battery come loose either.

 

PS - I do agree with DickW though; whilst you can put some stick and stick velcro on the battery itself to help position it roughly on initial insertion, that should never be the primary method of securing the pack. It always needs something wrapped around it to be certain it won't come adrift if the pack temperature rises.

Edited by MattyB
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1 hour ago, Rich Griff said:

A box with holes ?

 

A shelf giving enough support/strength ?

 

But point taken....cooling must be considered/designed in....but the battery must not fall/flung out....

 

 

Yes, please believe me that even a battery box with holes can dramatically affect battery cooling in a highly loaded powertrain with little internal volume such as an EDF or pylon model. In many cases there wouldn't be room for it at all; velcro or similar is the only option.

 

1 hour ago, Rich Griff said:

Seperate battery for Rx, motor battery on c of g....

 

There are times a separate RC battery is possible and desirable, but many times it isn't. Most smaller models will not be designed to have a separate RX battery, so you need to use the ESC BEC or separate UBEC. As long as you spec appropriate components based on the load from the servos this is no less reliable than a separate RX pack. Some pilots will contest it's more reliable because you always know the state of the RX power supply at the start of every flight, though for me I tend not to use the ESC BEC once the the model gets larger (for me that is anything that uses more than a 4S pck for the powertrain).

 

1 hour ago, Rich Griff said:

Ic for me for now thanks...

 

Fair enough, but if that is the case probably best that you leave advising the OP to those who do have practical electric flight experience to share. I certainly don't offer advice in the IC threads as my knowledge is low to non-existent... ?

Edited by MattyB
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On 15/09/2021 at 14:01, Upkeep said:

I had a prang the other day where the battery fell out during a loop, detached from the connector and the cub hit the deck nose first shortly after the battery.

There wasnt much damage to fix but now although the plane is flying great, it seems to be slower than before.

 

Same batteries, same charge etc etc. I wonder if the nose dive in to the field has damaged the motor ? Is that possible ? 

The motor spools up fine, isnt binding or making any strange noises.

 

Or maybe Ive missed something else ? 

 

Ta 

Being all electric, I have no interest in IC, I find the posts referring to IC confusing and of no use at all, have you got any further with finding an answer?

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Dunno how to re-set the ESC with the DXs

 

I've noticed that with the trim button in the neutral position, the motor wont fire up till its reached one of the lines on the gimble. Maybe 5mm ?

I'm wondering If at some stage I have inadvertently adjusted/re-calibrated the sticks somehow.  I can of course bring the throttle down with the trim bit im wondering if ive lost 10 % power as it is. 

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I'm afraid if you have out most things and I fail to see how the prang upset the esc unless the motor stalled and drew to much current. I would be inclined to try replacing the motor and esc if that brings it back to normal then try swapping the esc back se if the problem returns and don't forget as pointed out that the motor bearing may have suffered.

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