Re: Motor weight, size density?
Tony
I think F1B motors are somewhat similar to F1D and F1M in that the only restriction is total motor weight. I don't do F1D but for F1M I'm looking for the same result that Don S. talks about - the finished length of a motor. This assumes of course that you are going to make motors that weigh exactly what they are supposed to weigh. When I'm flying F1M I only look for the motor length and the test number generated by that motor.
As far as I'm concerned there is no way to compensate for inferior rubber in F1M. This not only refers to the batch of rubber but also to where a particular motor lies in the uncut strip. I had a run of excellent motors from a particular section of 5/99. Then the test results just went south and haven't come back. I also had several super motors from a section of 3/02 that were the best I've ever seen. None of my other 3/02 or 5/99 has ever equaled those.
The other indoor classes get a little stickier because there are no rules concerning the motor. This means that everything is a possible variable. Total motor weight can depend on your philosophy as much as what is really best. For instance at USIC I used 2.4 grams of rubber on my LPP while others were using 1.5 grams and getting similar results.
One advantage of having a wt/length number for a motor is to have a better idea of the maximum torque you can wind to. I don't have this figured out yet but it's pretty obvious that a motor with a higher wt/length will take more torque than a lighter one.
----- Original Message -----
From: Tony MATHEWS
To: indoor_construction_at_yahoogroups.com
Sent: Thursday, June 03, 2010 12:45 PM
Subject: RE: [Indoor_Construction] Motor weight, size density?
About 20 years ago we started going with a length per unit weight for our F1B models also. Again, the main issue was the inconsistency in the width of the rubber. You could change motors with the same number of strands and get different turns. More recently we have been doing a further specification to a pull force per unit length/weight to be able to compare motors. This is to try and get motors from different batches (with possible different stretch ratios) to match. I've made a crude rig that has a fixed length (with a cable) and a pull force meter attached to compare motors in my hand. The idea is that motors with the same force and the same length/weight should give more similar turns/torque.
The best method is to use specific energy/length (energy per unit weight per unit length) and make that the same for all motors by adjusting the width as needed. But that requires lots of testing...
Tony
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To: Indoor_Construction_at_yahoogroups.com
From: wdgowen_at_gmail.com
Date: Thu, 3 Jun 2010 11:29:17 -0400
Subject: Re: [Indoor_Construction] Motor weight, size density?
Thanks for the input Andras. My inclination now is to go with grams per meter. I'm not sure if I can overcome 70 years of using inches but I'll have a go at it.
----- Original Message -----
From: Andras REE
To: Indoor_Construction_at_yahoogroups.com
Sent: Thursday, June 03, 2010 6:52 AM
Subject: Re: [Indoor_Construction] Motor weight, size density?
Let me give some historical addition to the thread.
I started to use the g/m unit for the unused rubber about 45 years ago, here in Hungary, because I had the experience, the rubber measurement by the width is not accurate enough, in addition there are changes in the density and the thickness (now more than in case of the Pirelli). Maybe I was the first to do so, or at least one of them.
This way the comparison of motors or to make identical motors became more easy. Of course, who does not like the meter as length unit, it is easy to convert.to be comparable with the "rest of the world". Now there are two practices when giving data: for the whole motor section (I prefer and using this, because it does not depend on the number of strands) or the strand data. Having mainly two strand motors (loops), the conversion is easy in head.
Best regards
Andras Ree
On 2010. 06. 02. 18:41, olbill61 wrote:
I'm wondering if there is any way of describing motor weight per unit length that is more prevalent than others. The way I started out is by dividing total weight of a finished motor in grams by the motor length in inches. I think Kang has started using grams per inch for untied strip. I think Leo is using grams per meter.
Can any others who have switched to weight per unit length describe how they do it? I'm early in the process of doing it this way and could switch to a different system without much trouble. I'd like to hear from English and European fliers also.
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Received on Thu Jun 03 2010 - 10:20:59 CEST
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