Rubber Motors

[jmper29]

The specifications for my most recent version are as follows: Helicopter - Tornado, Modifications - Extra weight taken off the top section and putty added on the bottom, Rubber - 16' 2.4g loop, Winder - 15-1, Weight - 4.25g

I have two main problems. Firstly, my most recent rubber motor is much heavier (the last was 9') than the last and has lead to the helicopters bottom lifting up and essentially drawing out circles in the air. Secondly, I have approximentaly 650 winds left when the helicopter falls. I didn't have this problem with a shorter rubber band, yet the longer one performs better time-wise. I do not have access to thicker material.

Any help would be appreciated!

[jmper29]

The specifications for my most recent version are as follows: Helicopter - Tornado, Modifications - Extra weight taken off the top section and putty added on the bottom, Rubber - 16' 2.4g loop, Winder - 15-1, Weight - 4.25g

I have two main problems. Firstly, my most recent rubber motor is much heavier (the last was 9') than the last and has lead to the helicopters bottom lifting up and essentially drawing out circles in the air. Secondly, I have approximentaly 650 winds left when the helicopter falls. I didn't have this problem with a shorter rubber band, yet the longer one performs better time-wise. I do not have access to thicker material.

Any help would be appreciated!

[bjt4888]

The specifications for my most recent version are as follows: Helicopter - Tornado, Modifications - Extra weight taken off the top section and putty added on the bottom, Rubber - 16' 2.4g loop, Winder - 15-1, Weight - 4.25g

I have two main problems. Firstly, my most recent rubber motor is much heavier (the last was 9') than the last and has lead to the helicopters bottom lifting up and essentially drawing out circles in the air. Secondly, I have approximentaly 650 winds left when the helicopter falls. I didn't have this problem with a shorter rubber band, yet the longer one performs better time-wise. I do not have access to thicker material.

Any help would be appreciated!

Jmpr,

Good job supplying data. I'm assuming that your rubber motor is 16" long and not 16' long. Longer flight is a key criteria to evaluate when deciding next steps. Making large changes between test trials in science is generally not a good idea ("...is much heavier...").

Here is the data that I would need to give you very specific and helpful advice:

7. Rubber motor tied loop length (before use; not including knot)
8. Rubber motor mass in grams
9. O-ring(s) weight
10. Total maximum turns wound into the motor
11. Backoff turns
12. Maximum torque achieved in rubber winding
13. Launch torque
14. Remaining turns after the flight is complete

Brian T

[bjt4888]

Also, supply flight time. And, if you can, store your flight log in a google folder and supply the folder link so that I can see you log of data.

Brian T

[gwsci1]

In the referenced video, how does one calculate the rubber maximum allowed torque before breaking? Other than winding the rubber to the maximum number of turns and note the torque before breaking, is there a formula? Thanks!

[jmper29]

I didn't collect the rubber motor tied loop length before before making the knot. Additionally, my scale is not sensitive enough to detect the weight of my o-rings. Although, you may be able to recognize them based on this discription: clear, hardly fits on the band, comes with the kit. Starting with my most recent test, I'm doing 5 backoff turns. Before that, I did none. The launch torque of my most recent test was about 1.1. I don't have the maximum torque achieved yet (I will look into how to get that correctly). The only really reliable info on the flight log attached below is the most recent flights.

Finally, with my last flight, everything looked good except for the fact that, even with more or less putty on the bottom, the helicopter will not stay straight. Before replacing the vane and a propeller, this wasn't a problem.

Thank you!

[coachchuckaahs]

Without looking in long detail here, it would appear that you are not winding nearly enough.

You are reporting turns on the winder, but not turns on the rubber motor. SO rules REQUIRE turns on the motor at launch. You do not report a winder ratio, so it is impossible to guess how many turns on the motor. Be sure before competing that you report turns on the motor, not on the winder.

Whether you have a 15:1 or 10:1 winder, you are nowhere near max turns. Review the winding video on the NFFS channel, and look at the max turns calculator on the NFFS site.

The winds remaining will go up with lower density motors, and/or higher mass motors, as your data shows (with your longest motors having more turns remaining). However the "correct" or "best" turns remaining will be shown by the stopwatch. I suspect you will find that a 30" long motor (presumably about 15" or 38cm after tying) is a bit long to be optimum.

Work on your winding technique per the videos. You should be getting 1500-1700 turns onto a 15" loop at 2.6g. It appears you are getting 750 (10:1) or 1125 (15:1). This is leaving a lot of time on the table.

Coach Chuck

[jmper29]

Thank you both for all the help! I have been looking into getting more wing material. Do you know of a good place to buy it from?

[coachchuckaahs]

I am sorry, I am not sure what you mean by "wing material", as there are no wings on the heli.

I can assume you mean the rotors, but I do not know if you want covering material, balsa, carbon, etc.

The covering is generally available as "Ultrafilm" from several indoor suppliers, including Indoor Freeflight Supply, Indoor Specialties, and FAI Model Supply. The SO kit makers may also sell covering, such as J&H and FFM. There is also a more expensive "Super Ultrafilm", which is lighter but harder to handle and more expensive. Such a small amount of covering is used here, and the weight minimum very easy to reach, you really won't gain anything with Super. In a pinch, you can use veggie bags from the produce section of your grocer.

The carbon can be had from IFFS (https://www.indoorffsupply.com/shop/500mm-carbon-rod), CSTSales.com, or possibly the SO kit makers.

A glossary of terms for heli is on the NFFS web site at https://www.freeflight.org/wp-content/u ... ossary.pdf

Coach Chuck

[jmper29]

I meant covering material originally. My kit came with veggie bag I believe. I am not sure if it is the best option for the covering material. Additionally, I need my covering material to come in preferably a week. Do you know of a good place to buy this material and which (e.g. veggie bag) I should buy?

Thank you!