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        Question Where can I find: Number of turns rubber can handle and a rubber stripper?

#1 Majortomski Dec 13, 2012 07:52 AM

Where can I find: Number of turns rubber can handle and a rubber stripper?
 
First get your mind out of the gutter! :p

By rubber stripper I mean a cutter that will thin the standard availble 1/16, 1/8, 1/4 inch wide rubber into smaller widths?

And is there any data out there on how many turns can be put in a given size rubber band before it breaks?

For instance if I've go a 10 inch loop of 1/16 in my peanut model what is the maximum safe number of winds I can put in it everytime and not fear it breaking?

TIA

Tom

#2 Norm Furutani Dec 13, 2012 11:23 AM

I use a Ray Harlan stripper. Works great, and may be the only commercial unit available.
http://www.indoorspecialties.com/index1.html

The Hippocket forum is a great place for FF info. Here's a link to a homemade stripper.
http://www.hippocketaeronautics.com/...ic,9209.0.html

Can't help with the rubber winding, except to wind a sample outside of the plane. When winding in the plane, use a winding tube to protect it.

- Norm

#3 BMatthews Dec 13, 2012 01:12 PM

There used to be charts for the turns per inch for a few different cross sections. But so much depends on the qualities of each batch of rubber that these days those charts mean little. Also to some extent the number of turns you can get into a motor depends on how slack it is between the hooks.

So there's really nothing more to do than to make up a sacrificial test motor and wind it correctly and go until you feel it tighten up with the strong rise it creates just before it snaps or to wind through that point until it breaks and then figure out your own 80% max turns for a safe winding for the models.

At 80% of max you can wind and fly all day long with very little risk. But you do want to inspect for edge tears every couple of flights and especially at the end of the day. Small nicks and "hairs" of rubber at not a big deal unless they extend across the entire edge surface to connect the two faces. When you see that sort of nick in the edge then toss the motor.

As for stripping the rubber down you can try the pull through a single blade styles. But in the end you'll likely find, like I did, that the Harlan style strip cutter is the way to go. I always got variable results with the fixed blade pull through styles to where I had only questionable control over the final width. 5 to 10 thou of variation over a few inches was not at all uncommon with the pull through styles I tried to make. And that simply wasn't good enough for the EZB's and microfilm models I was flying back then. For penny planes and indoor scale it's likely fine but I soon gave up trying to strip my own and simply used to buy the envelopes of pre-stripped rubber from the indoor specialty places back then.

#4 Majortomski Dec 14, 2012 06:27 AM

Thanks guys. I guess that $5.50 per projected remaining year of my life isn't too much to pay for a stripper.

B Matthews I happended to inherit some of those pre thinned strip packages and I was amazed how well it improved how my planes flew.

#5 BMatthews Dec 14, 2012 12:42 PM

What colour is the rubber in the packs? If it's the old darker brown honest to gosh Pirelli then you might just have something rather special. The old Pirelli, as I recall, did not like to take as many turns per inch as the better batches of tan rubber we have now. It also built up more torque for a given number of turns. So in general it might make the models SEEM to fly better. But that's only because they are climbing more strongly due to the added torque. But the motor run will be shorter as a result unless you make the motor longer by a little than the tan motors. Or go for a slightly smaller width.

Then again we've all seen how variable the tan rubber can be from maker to maker and batch to batch. So even if it's tan rubber it might just be an especially good batch from some time back.

#6 Harri3 Dec 14, 2012 01:20 PM

A torque meter is probably more useful than counting turns. I've never owned one but toyed with getting or making one. Haven't done either yet.

There was an article on rubber thickness and torque in the latest Flying Aces newsletter that you might find useful. I don't have it handy now though. If you're interested I will try to locate it.

#7 Majortomski Dec 14, 2012 04:45 PM

I guess I should join Flying Aces too.

Harri3 what is that plane in your avatar?

#8 Harri3 Dec 14, 2012 05:06 PM

Flying Aces has several plans (for rubber powered free flight) in each issue and some tips usually. The planes pictured are amazing in detail, plus they fly good. My planes don't look a quarter as good and don't usually fly so good. It come s out 6 times a year.

I'll try to locate the issue with rubber motor thickness and torque and scan it for you. It will give you an idea of what's in an issue.

The plane in my avatar is a friend's 1949 Piper Clipper.

#9 Gluehand Dec 16, 2012 03:16 AM

1 Attachment(s)
This table was published in Flying Models Magazine, as well as in the well known book by Don Ross.
Of course rubber quality varies, but as a rough guide it is very useful.

:)

#10 Majortomski Dec 16, 2012 02:45 PM

Cool! thank you! that table saves a lot of sacraficial windings!

#11 algy2 Dec 16, 2012 07:32 PM

Winding rubber motors
 
3 Attachment(s)
Hi,
Noticed this thread taking place on winding rubber motors, torque and safe turns so have scanned some information from three of the many books in my collection.

The first is taken from WILLIAM F. McCOOMB’s “FLYING AND IMPROVING SCALE MODEL AIRCRAFT“ 1977.

Now long out of print but if you ever get the opportunity to acquire a copy grab it. It’s loaded from cover to cover with incredibly detailed information and advice.

The next article comes from “THE MODEL AIRCRAFT HANDBOOK” by HOWARD G. McENTEE 1960.

The final chapter is taken from the “MODEL AEROPLANE MANUAL" by LAWRENCE H. SPARY and CHARLES A. RIPPON third edition. Not sure when this book was first published but possibly in the 1930s.

Hope it is of help.

Cheers

Algy

#12 Majortomski Dec 17, 2012 06:49 AM

Thanks Algy! Ironic the cover of the first article has a Fairchild 24 on the cover. I grew up with a F-24 in our garage. Dad's "someday" going to get restored project.

#13 Harri3 Dec 28, 2012 08:54 AM

1 Attachment(s)
MajorT

Attached is the Flying Aces article on using torque to determine max winds. Sorry it took so long.

Here's a link to tips from the Pensacola Free Flight Team, You can spend a lot of time here. http://www.pensacolafreeflight.org/page5/page5.html

There's an article for building a torque meter there, in case you might want to give it a go. I've never built one.

Good luck!


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