I gotta jump in here. If you ask any indoor flyer what rubber he is using, the answer always comes out .085, or such. As Bill Gowen points out, it depends on the batch. Not because of different densities, but because of different thicknesses. It can vary in the same batch. So here is what I do and what I put in the instructions for my rubber stripper.
Decide on the approximate length of motors for your model. Add a couple of inches or more and cut a number of strips. Ten from 1/8" rubber or 5 from 1/4" will do for a start. This method will waste some rubber, but make up for it in consistency of cuts.
Weigh these strips and put them on the bench in order in increasing weight. This will be an eye-opening experience. The weights may range 10% or more and all from contiguous strips! No wonder most people have trouble cutting consistent motors. And the guy who just uses a micrometer to measure rubber is totally lost when changing motors.
Since few modelers give info on weight per inch, here is the only place to use a micrometer to measure rubber. If you have a new model that has no motor history, you need to start somewhere. Make a guess about the rubber width. Cut a piece of rubber about 2" long. Set the stripper to about where you think the cut should be. Strip the short piece. Now use a micrometer to check if the cut is close in width. Hold the strip with four fingers, thumb and third finger at one end, first and second fingers at the other. Adjust the micrometer until the rubber has a touch of friction going through the faces of the micrometer (for motors about .040:, be sure to measure the right sides of the rubber). If it needs a tweak, adjust the stripper and cut another short piece. When satisfied, cut the first strip of motor stock.
Weigh the cut strip, mark an envelope with the rubber batch, length of strip, weight, and calculate weight/inch, writing it down also. Put the motor in it. If the stock strip left over is wide enough to get a second motor, put it back down on the bench where it was. If the weight of the first strip wasn't quite right, adjust the stripper a bit and cut the next strip. After a while, the strips will be very close to the target weight. But note that the uncut strips are getting heavier, so the stripper needs to be adjusted to slightly smaller strips. When all of the strips have been cut once, start again with the last strip (if cutable) and start again. The width will not be the same as for the last cut, because narrower strips don't cut the same as wider strips. You will need to adjust the stripper to a little narrower strip. After a few strips, you should get some consistency again. Note that this time, as you progress down the strips, they are getting lighter, so the width needs to be increased a bit. All of this must sound pretty ominous. After some practice, it will get easier. The consistency will be quite good. It isn't hard to get a bunch of motors with weights ranging plus or minus 1% (after a few strays are culled out).
If you take notes about number settings on the stripper, and strip results plus stock weight, you can get back to accurate cuts in another cutting session very easily.
The best part of all this is that when flying and you break a motor, you can pull out another one, break it in and expect to see the same performance as the one that broke. A very common comment heard on the floor is "I don't understand it. I just put the same size motor on it and it only went halfway up" That guy has a micrometer in his pocket!
Ray
--- In Indoor_Construction_at_yahoogroups.com, "jabiruchick" <jabiruchick@...> wrote:
>
> Ok, that makes sense... the precision you guys apply to this stuff is mind boggling! You all must get really annoyed when people just assume you pull a #64 rubber band out of the office drawer and hook it on there! :-D (I hate it when people ask me that)
>
> KT
>
> --- In Indoor_Construction_at_yahoogroups.com, Nick Ray <lasray@> wrote:
> >
> > Katie,
> >
> > The gram size is to standardize across rubber batches. For example a 1 gram
> > .050" strip of 5/99 will be shorter than a 1 gram strip of .050' 2/99. The
> > density helps to (some what) equivocate rubber sizes between batches.
> >
> > Nick
> >
> > On Tue, Apr 27, 2010 at 5:18 PM, Don DeLoach <ddeloach_at_> wrote:
> >
> > >
> > >
> > > Katie
> > >
> > > You can buy a cheepie electronic gram scale for peanuts on eBay and
> > > elsewhere online! For indoor building/flying you'll need one with 0.01-gram
> > > resolution.
> > >
> > >
> > >
> > > Another idea: Ralph Ray (the Tustin Hangar guru) has some scales for sale.
> > > Not sure if they are .01-gram or not, but you should contact Ralph and see.
> > > Proceeds go toward the very expensive Tustin hangar rental.
> > >
> > > ralphray_at_
> > >
> > >
> > >
> > > P.S. still have that neat Pasped Skylark?
> > >
> > >
> > >
> > > Rgds
> > >
> > > Don DeLoach
> > >
> > > Editor,* *NFFS *Free Flight Digest*
> > >
> > > Freelance Commercial Writer
> > >
> > > 831 E. Willamette Ave.
> > >
> > > Colorado Springs, CO 80903
> > >
> > > 719.964.7117 voice
> > >
> > > ddeloach_at_
> > >
> > >
> > > ------------------------------
> > >
> > > *From:* Indoor_Construction_at_yahoogroups.com [mailto:
> > > Indoor_Construction_at_yahoogroups.com] *On Behalf Of *jabiruchick
> > > *Sent:* Tuesday, April 27, 2010 12:40 PM
> > > *To:* Indoor_Construction_at_yahoogroups.com
> > > *Subject:* [Indoor_Construction] Re: A-6 Motors
> > >
> > >
> > >
> > >
> > >
> > > Cool-- thanks!
> > >
> > > Another newbie question. I noticed lots of people are posting their motor
> > > sizes using a length and weight in grams as you did below. How do you cut a
> > > motor to a gram size, as opposed to setting a stripper to a certain width?
> > >
> > > KT
> > >
> > >
> > >
> > >
> >
>
Received on Wed Apr 28 2010 - 10:55:27 CEST
This archive was generated by Yannick on Sat Dec 14 2019 - 19:13:46 CET