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Were all of the helis that got close to 3 minutes modified FFM kits, or were there original designs?

Ten086 wrote:Were all of the helis that got close to 3 minutes modified FFM kits, or were there original designs?

Nearly all of them would be FFM kits, not necessarily modified though.

alylam wrote:

Ten086 wrote:Were all of the helis that got close to 3 minutes modified FFM kits, or were there original designs?

Nearly all of them would be FFM kits, not necessarily modified though.

Wow, 3 minutes with an unmodified kit? I’m really stuck on how to increase the time of an unmodified kit helicopter so significantly by this point...I’d assume just really good testing and motor choice?

Ten086 wrote:

alylam wrote:

Ten086 wrote:Were all of the helis that got close to 3 minutes modified FFM kits, or were there original designs?

Nearly all of them would be FFM kits, not necessarily modified though.

Wow, 3 minutes with an unmodified kit? I’m really stuck on how to increase the time of an unmodified kit helicopter so significantly by this point...I’d assume just really good testing and motor choice?

Ten, what times are you getting right now? I've broken 2 minutes but like you said getting to 3 seems really tough without mods

Dave reported during development times on the order of 2:40 with prototypes weighting around 3.5-3.6g.

It is all about optimizing the rubber strength (width) and length against your particular rotors. More rubber means more turns, but more weight, so each given rubber width will have an optimum length.

You also must be winding for full performance. Other posts here and in Wright Stuff have talked about winding. Stretch, wind to just before breaking, while walking in. You have to know what torque will break the rubber and stay short of that. then after wound tight, unwind to your launch torque. Winding just to launch torque will only get 50-60% of the winds that over-winding and backing off will get.

Coach Chuck

coachchuckaahs wrote:Dave reported during development times on the order of 2:40 with prototypes weighting around 3.5-3.6g.

It is all about optimizing the rubber strength (width) and length against your particular rotors. More rubber means more turns, but more weight, so each given rubber width will have an optimum length.

You also must be winding for full performance. Other posts here and in Wright Stuff have talked about winding. Stretch, wind to just before breaking, while walking in. You have to know what torque will break the rubber and stay short of that. then after wound tight, unwind to your launch torque. Winding just to launch torque will only get 50-60% of the winds that over-winding and backing off will get.

Coach Chuck

Any idea what kind of ceiling he got 2:40 on? I'm literally just testing at home in my basement because the ceiling is at least flat. (Reveur, unfortunately I'm not supposed to say anything about my time because our rival school might see...it also varies a lot based on ceiling height, so I'm not sure what ceiling height most people are testing in when they report their times.)

Speaking about torque, I got the "dirt cheap torque meter" and assembled it, but I've been kind of confused while using it. Winding clockwise versus counterclockwise has never been consistent for me--I think the counterclockwise winding has always increased more quickly. There's also always a little bit of torque before I even start winding. Did I just assemble the torque meter wrong??

I believe Dave's testing was with an 8-foot ceiling at his home. We have seen similar times with 8' ceiling. We test at home, but there are many obstacles, so sometimes we test at an office where we can clear out the chairs and tables, but still an 8-foot ceiling. A 20 foot ceiling may add 10-15 seconds.

I do not have the "dirt cheap" torque meter, but I suspect it is of the wire-twisting variety. I would look at how the rubber sits on the hook when winding each way. If the rubber (or o-ring) climbs the hook in one direction but not the other you could get different results. If it does, try adjusting the hook shape until it stays centered throughout winding. Possibly put solder blobs or small washers soldered on to center the O-ring.

Also look at any binding in the torque meter when going one way or the other. You could build a simple lever and weight assembly to test the torque meter in each direction to ensure it is reading the same both ways. We use a lever on a bearing-pivoted shaft, and that lever pushes on a gram scale. The bearing assembly came from junk boxes in the garage, probably from an electric R/C plane gearbox. The lever length is set to read out in oz-in when on the gram scale. Simple, but not as simple as the wire type. Still, most often the readings are wrong if the O-ring gets off center, or if the rubber is not pulled straight with the shaft.

Can the dial be re-centered? Or is the needle on 0 until you stretch the rubber, when you say "before winding"? We sometimes see a reading when stretching before winding, usually caused by off-center O-ring or off-straight stretching.

Coach Chuck

coachchuckaahs wrote:I believe Dave's testing was with an 8-foot ceiling at his home. We have seen similar times with 8' ceiling. We test at home, but there are many obstacles, so sometimes we test at an office where we can clear out the chairs and tables, but still an 8-foot ceiling. A 20 foot ceiling may add 10-15 seconds.

I do not have the "dirt cheap" torque meter, but I suspect it is of the wire-twisting variety. I would look at how the rubber sits on the hook when winding each way. If the rubber (or o-ring) climbs the hook in one direction but not the other you could get different results. If it does, try adjusting the hook shape until it stays centered throughout winding. Possibly put solder blobs or small washers soldered on to center the O-ring.

Also look at any binding in the torque meter when going one way or the other. You could build a simple lever and weight assembly to test the torque meter in each direction to ensure it is reading the same both ways. We use a lever on a bearing-pivoted shaft, and that lever pushes on a gram scale. The bearing assembly came from junk boxes in the garage, probably from an electric R/C plane gearbox. The lever length is set to read out in oz-in when on the gram scale. Simple, but not as simple as the wire type. Still, most often the readings are wrong if the O-ring gets off center, or if the rubber is not pulled straight with the shaft.

Can the dial be re-centered? Or is the needle on 0 until you stretch the rubber, when you say "before winding"? We sometimes see a reading when stretching before winding, usually caused by off-center O-ring or off-straight stretching.

Coach Chuck

Sorry for the late reply!

I'm not quite sure what you mean by the O ring climbing the hook, I tried to look at it while winding but I don't think the O ring moves much? The side view of the hook is like this shape: _\ with the O ring sitting at the corner.

Also not sure how to build a lever/weight assembly...any chance you could post a picture?

I think I might've been pulling off-straight a bit! I tried to adjust my angle which helped some. I also tried adjusting the hook to be more straight, which seems to have helped too--I probably just didn't bend it very well when assembling it, or it got bent during transportation. It seems to be a little more consistent both ways when starting off, but is still not ending at the same value for the same number of winds counterclockwise versus clockwise..?

I also realized I'm not sure how to use the torque meter when you stretch the motor out really far and walk in, because doesn't changing distance as you wind change the rate at which the torque changes, so you won't end up with that S curve that people have mentioned before?

Sorry, I'm just really confused about torque meters...I also haven't learned about torque yet in physics, so I'm very sorry if my questions don't make any sense :')

I have had some hook shapes where, depending on the o-ring type (we use hard plastic), they can walk off center or up one side of the hook. Sounds like that is not your issue.

Stretching the rubber allows you to pack more turns in as you wind. The torque still follows the general curve, but you need to "follow the feel". Generally, we stretch to 7-8 times original length, wind about half the full winds at that position. You will feel a sudden sharp increase in the pull, and may see the torque coming up faster. This is the signal to move in. You can "follow the pull", continuing to give a little as the pull increases. Or we will read the torque at the sudden pull, and then walk in trying to keep that torque steady as we walk. Around half way in, the torque will start rising faster. At this point you should have about 3/4 total turns on, and you walk in a lot faster. As you get to the final length, you finish the winds. Additional winds to "just get one more turn" on a tightly wound motor at flying length usually means we are making new rubber. The final torque is usually about twice the "big pull" torque that told you to start walking in.

Then, using the torque meter, unwind to your desired launch torque.

Are you getting different numbers with same piece of rubber?If so I would definitely look for something off center that would cause this, or something binding.

Here is one version of a digital scale torque meter. There are other, perhaps simpler methods: http://www.stickandtissue.com/cgi-bin/y ... 38903415/6

Coach Chuck

2 min 14 seconds, with chinook, black panels, and 10% bonuses placed second at the New York State competition