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The Ohmen

My first electric powered aerobatic model

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Old Geezer04/05/2018 00:02:24
670 forum posts

Oh - and usually if the stand-offs are long enough you have room to tuck the ESC in behind motor where nature intended - then a couple of strategically placed 'oles and the cooling's sorted out too.

Edited By Old Geezer on 04/05/2018 00:08:10

Peter Miller04/05/2018 08:15:17
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Er, Fibreglass cowl??

Well, yes, I can see that for ARTFs or Kits which have such things.

I did need stand offs the get the motor in the right place on my Veron Deacon. It was also useful for wrapping lead round to get the CG in the right place.sad

Nigel R04/05/2018 10:25:06
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Have to say, I agree with the above, I think 3S2200 is a bit anemic for a 3lb aerobat, unless you're happy with very short flights.

Andy4804/05/2018 10:27:52
1571 forum posts
1 photos
Posted by Peter Miller on 03/05/2018 21:08:44:

Andy.

Let me know how you get on with the Peggy Sue build please.

BEB

Well there is space round the electrics but adding a battery would be almost impossible without major surgery.Might get a 3300 battery in but I must check on the size

Hmmm, I think the word is slowly! Currently very involved in family issues. I got the short kit of SLEC, and am on with the wings at the moment and all looking good. Putting small servos in each wing half rather than a crank system. Am thinking of dropping the battery at an angle from above by removing the wing. This will save a fiddly hatch somewhere, and give plenty of room for the current sensor which is about 6cm long and has to plug in between the battery and the ESC.

As for motor mounts, I have found by far the simplest way is M3 threaded rod made out of stainless steel and M3 locking nuts. This is about £2.50 per 20cm, and forms a very rigid mounting for this size of motor. This arrangement allows for any downthrust or sidethrust and to adjust the motor forward and backward to suit CofG. In a nosedive, the rods bend, but the motor usually remains undamaged. With this arrangement it is often better to test fly the plane without any cowl, and when all is correctly set up, then build one to make a perfect fit.

Nigel R04/05/2018 11:06:53
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B&Q, M4 rod, £1.55 / meter.

Peter Miller04/05/2018 12:19:39
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Sounds good Andy

Mine has no side or down thrust but then I never do.

Peter Miller04/05/2018 12:20:56
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Nigel

I have a feeling that the model will be well under 3 lbs.

Andy4804/05/2018 14:23:05
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Posted by Nigel R on 04/05/2018 11:06:53:

B&Q, M4 rod, £1.55 / meter.

B&Q don't sell M3 rod, and this is stainless steel which is tougher.

M4 rod would involve drilling out the motor back plate, and the nuts end up very close to the motor body. This is particularly difficult if one uses locking nuts as they have a greater depth.

Andy4804/05/2018 14:25:50
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Posted by Peter Miller on 04/05/2018 12:19:39:

Sounds good Andy

Mine has no side or down thrust but then I never do.

Have to admit I'm curious about this, and I know BEB did something on this forum about it which involved a heated debate. I'm strongly leaning towards your way of thinking. Will put no side/down thrust on Peggy S.

Peter Miller04/05/2018 18:14:01
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On Peggy Sue the thrust line is not very far below the centre of drag so there is no great moment arm to thust the nose up.

Side thrust is to stop a tendency to swing to the left. I simply use a small dab of right rudder on take off.

Even my RWD5 did not need down thrust.

So these things go against what the experts say. All I can say is that it works fro me.

Nigel R04/05/2018 19:03:26
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Stainless is tougher than normal steel? I thought they were the same. If anything stainless being more brittle.

Either way m4 nuts - normal ones - are an admittedly tight but nevertheless usable fit on a 35 dia motor.

I've never bothered with luck nuts but that's another debate.
Peter Miller12/05/2018 14:49:41
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Well, an up date on The Ohmen. The model is almost complete. covering done, all installation done. Just got the cowling and windscreens to do.

The CG came out a fraction in front of the designed location, I didn't expect that!! Saves moving the motor forward which is great.

Weight at the moment is 2 lbs 9 oz and it will only go up by about an ounce or two so well under design target of under 3 lbs.

Peter Miller21/05/2018 14:43:35
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Well it is finished and test flown

In spite of doubts about the CG it actually came out a fraction nose heavy so 20 grams of lead in the tail fixed that

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Fully aerobatic on half power, Does spins of all types with instant recovery on releasing the sticks. Low level inverted was performed within minutes of starting the flight. THat shows the confidence of Stuart who flies my models for the camera.

Former Member21/05/2018 14:53:06
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[This posting has been removed]

Peter Miller21/05/2018 14:59:48
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Thank you

Nigel R21/05/2018 16:12:55
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Looks fabulous, nice one. AUW is good too.

Million dollar question - what flight times are you getting on that 3S2000 ?

kc21/05/2018 17:03:13
6956 forum posts
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The really important question is ............when is it going to be published in RCME?

Peter Miller21/05/2018 18:10:00
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Posted by Nigel R on 21/05/2018 16:12:55:

Looks fabulous, nice one. AUW is good too.

Million dollar question - what flight times are you getting on that 3S2000 ?

Not sure as to the actual flight times but I can tell you that at maximum power on the ground the motor was drawing 25 amps. Most of the time the model was aerobating on about half power and flight timjes were quite reasonable. Batteries were at 11.8 volts after the flights.

I think you can safely say that you will get very reasonable flight times. Next time I will time the flights and check voltage at the end.

Peter Miller21/05/2018 18:14:25
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KC

RCM&E will be using my Easter Eagle Senior in August. THen they have Little Miss Honky Tonk. I still have the plans to complete and the article to write. AS for the WHEN That is up to the Editor.

Peter Miller25/05/2018 18:29:24
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Did some more flying today and got some better data.

I had two flights. The model is aerobatic on half throttle and only needs full power for things like square loops and they really are nice and square.

A flight of eight minutes left me with 11.4 volts in the battery.The first flight was slightly shorter at 7 1/2 minutes and I didn not use full power as much. that left 11.8 volts.

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