Helicopters B

jander14indoor
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Re: Helicopters B

Post by jander14indoor »

1) Slight difference in turns per inch, if lube properly, not enough to worry about. Torque meters. There are a couple of suppliers out there, but I usually just build my own, see viewtopic.php?f=68&t=1822 for discussion of plans available on line.
2) How good are your times? If you are up in the two minute range, I think you have the answer. With data. The only difference I've seen is with both rotors free they spin around the same axis and seem to wobble less. POSSIBLY increasing flight times slightly.

Jeff Anderson
Livonia, MI
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Re: Helicopters B

Post by Inergy9118 »

jander14indoor wrote:1) Slight difference in turns per inch, if lube properly, not enough to worry about. Torque meters. There are a couple of suppliers out there, but I usually just build my own, see viewtopic.php?f=68&t=1822 for discussion of plans available on line.
2) How good are your times? If you are up in the two minute range, I think you have the answer. With data. The only difference I've seen is with both rotors free they spin around the same axis and seem to wobble less. POSSIBLY increasing flight times slightly.

Jeff Anderson
Livonia, MI


The link for the Torque meter is not working. Worried we can not get the rubber we need in time. Who do you recomend for suppliers of rubber?
Last edited by Inergy9118 on April 9th, 2013, 4:11 pm, edited 2 times in total.
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Re: Helicopters B

Post by mrsteven »

With only a minute, I wouldnt worry about those issues yet, I would concern yourself in making better helicopters to match to whatever rubber size you are using and optimizing it. The difference in 2 free and 1 free rotor is insignificant in my experience as well.

I use FAI rubber, http://domino-35.prominic.net/A55C2D/fa ... 42006D1051
A 1/4 lb will be more than enough to last a season. Ignore the 10/5/1lb and the prices. A 1/4'' is about $10 and is good for a long while.
Over 2 years of it and testing almost every day I think I totaled out at maybe 1/2lb of rubber. Possibly more but not by much. Though if time is an issue I would find local hobby shops and use whatever they have available and match the helicopter to it
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Re: Helicopters B

Post by Inergy9118 »

HELP. What is the key of getting over a minute? We have tried a lot of things. What is the key? How many turn per inch should you have?
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Re: Helicopters B

Post by retired1 »

I normally use a value of 100 turns per inch, but this batch of rubber is breaking at 94 TPI, so our team used 90.

That assumes a lubricated band that has been prestretched after tieing the knot.

Better times are achieved by having the chopper as close to the 3 g min as possible, having the blades absolutely symmetric, a proper pitch and having the right width and length of rubber for your chopper.

Are you using a kit??
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Re: Helicopters B

Post by Inergy9118 »

retired1 wrote:I normally use a value of 100 turns per inch, but this batch of rubber is breaking at 94 TPI, so our team used 90.

That assumes a lubricated band that has been prestretched after tieing the knot.

Better times are achieved by having the chopper as close to the 3 g min as possible, having the blades absolutely symmetric, a proper pitch and having the right width and length of rubber for your chopper.

Are you using a kit??
Used a kit a first but it 's instructions were not good. Now using what was given at workshop with some modifications. Our copters are around 3.1. I read on this blog to use 2-4x motor stick legnth for the rubber, is that true? How do you do that with out the rubber hitting the Motor stick?
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Re: Helicopters B

Post by jander14indoor »

Again, THERE IS NO RELATION BETWEEN RUBBER BAND LENGTH AND MOTOR STICK LENGTH. They don't have to match, they don't have to be specific ratios to each other. NO relation.

TYPICALLY, you want your motor stick to be only long enough to stabilize things, around 10 to 12 inches for this years rules. The rubber motor is then matched to the rotor to maximize time and is TYPICALLY longer than the stick.

It does not hit the stick because you space it away slightly AND because it shortens a LOT in the first turns where little energy is stored. By the time you get it fully wound you will have to stretch it to get it on the stick and the tension will hold it away from the stick.

Jeff Anderson
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Re: Helicopters B

Post by Hosj »

Does the data you turn in have to come from one of the copters you run at the competition?
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Re: Helicopters B

Post by Hosj »

Yet another question, sorry. :oops:

if I use the freedom flight model with 4 baldes on the upper rotor, shouldi have the bottom rotor be free or fixed to the motor stick? We got 55 seconds and 2nd at regionals with a 2 bladed fixed design, so maybe we could do better if it was free?
Nationals 2013: Meteorology 2nd, Water Quality 7th, Dynamic Planet 28th, Helicopters 41st
Nationals 2014:Hydrogeology 8th, Game On 25th
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Re: Helicopters B

Post by jander14indoor »

Not official, opinion only, see soinc.org for official FAQs, etc, but...
Hosj wrote:Does the data you turn in have to come from one of the copters you run at the competition?
Nothing in the rules says it has to be from the copters you compete with, and I've never seen a log rejected for that reason. HOWEVER, that doesn't prevent some event supervisor I've never met (and there are a lot) from scoring that way.

Perhaps more importantly, WHY WOULD YOU WANT TO COMPETE WITH A HELICOPTER YOU HAVEN'T TEST FLOWN? That's just crazy. And if you test fly it, wouldn't you have data you could document in a log? And if so, why WOULDN'T you present that data?

There is NO risk providing MORE than the requested data, so why not? If an event supervisor rejects a log with 5 flights from copter one, 7 flights from copter two, 2 from copter three... and less than five flights from copter n-1 and less than five from copter n and you are competing with copter n-1 and n then you had no chance with that supervisor ANYWAY.

If you are worried about the event supervisor keeping your log (no reason to, but again, I'm one voice) just make a copy to present for the tournament.

Again, my opinion.

Jeff Anderson
Livonia, MI
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