Cox Propellor

ian1954 Sat Jun 29, 2013 4:29 pm

Be careful.

Interesting incident today, Propellor blade sheared off while bench running my Hiscott Medallion! Can't find the blade that sheared off!

Cox Propellor Brokpr10

It seemed very flexible and not brittle in anyway.

It has 'Cox Hobbies Inc' on it - I have quite a few!

SuperDave Sat Jun 29, 2013 5:10 pm

Black Cox "rubber duckie" props are intended for general use; gray are for competition flying. It's quite usual to have one shear.

SD

(If you were thinking of finding the missing blade then glueing it back on FORGET IT!)

lol!

smooth_bill Sat Jun 29, 2013 5:20 pm

ian1954 wrote:Be careful.

Interesting incident today, Propellor blade sheared off while bench running my Hiscott Medallion! Can't find the blade that sheared off!

It seemed very flexible and not brittle in anyway.

It has 'Cox Hobbies Inc' on it - I have quite a few!

If those are original Cox props they may not be safe to use.

Bernie has new props at bargain prices. My favorites are the rubber ducky flexible props, and I've yet to break one.

Bill

**Cribbs74** Sat Jun 29, 2013 6:15 pm

check the ceiling......

pkrankow Sat Jun 29, 2013 7:11 pm

I have a number of Top Flite propellers that are suffering the same fate. I have not tried boiling them in water yet, but simple soaking did not change the failure mode.

The nylon is supposed to absorb water improving its pliability and resilience. In fact, soaking NEW propellers does improve the durability of them. I soak nylon props overnight then keep them in a zip lock bag. The new propellers are more supple after soaking. The treatment is also supposed to be good for glass or polyester filled nylon props.

Phil

JPvelo Sat Jun 29, 2013 7:47 pm

pkrankow wrote:I have a number of Top Flite propellers that are suffering the same fate. I have not tried boiling them in water yet, but simple soaking did not change the failure mode.

The nylon is supposed to absorb water improving its pliability and resilience. In fact, soaking NEW propellers does improve the durability of them. I soak nylon props overnight then keep them in a zip lock bag. The new propellers are more supple after soaking. The treatment is also supposed to be good for glass or polyester filled nylon props.

Phil

If the props absorb water wouldn't affect the balance?

Jim

Cox International Tue Jul 02, 2013 11:31 pm

ian1954 wrote:Be careful.

Interesting incident today, Propellor blade sheared off while bench running my Hiscott Medallion! Can't find the blade that sheared off!

It seemed very flexible and not brittle in anyway.

It has 'Cox Hobbies Inc' on it - I have quite a few!

Did you purchase them from us?

ian1954 Wed Jul 03, 2013 5:15 am

Cox International wrote:
ian1954 wrote:Be careful.

Interesting incident today, Propellor blade sheared off while bench running my Hiscott Medallion! Can't find the blade that sheared off!

It seemed very flexible and not brittle in anyway.

It has 'Cox Hobbies Inc' on it - I have quite a few!

Did you purchase them from us?

I did but I am not seeking any redress. Just a warning to be careful where you stand when close to a running engine.

Plastic, nylon etc. are strange materials and anything that is cast or moulded is suspect. There is no way of checking for perfection unless you have X-Ray vision. One in many hundreds of chances of this happening.

This did not hit me, I didn't even see where it went (haven't found it yet either!). In front or behind the propellor is probably the safest position. I once took a splinter in the back of my hand from a wooden propellor. I was smoking a cigarette - it could have been my jaw!

Cox International Wed Jul 03, 2013 9:23 am

There have actually been issues with those props as they are old Cox stock.

We test-bend each one and have about 25% failure rate. Only a few hundred left and we are getting new ones moulded.

Please identify yourself to us by email to support@coxengines.ca with perhaps either an order # or order date. We will then send replacement props.

pkrankow Wed Jul 03, 2013 10:06 am

JPvelo wrote:
pkrankow wrote:I have a number of Top Flite propellers that are suffering the same fate. I have not tried boiling them in water yet, but simple soaking did not change the failure mode.

The nylon is supposed to absorb water improving its pliability and resilience. In fact, soaking NEW propellers does improve the durability of them. I soak nylon props overnight then keep them in a zip lock bag. The new propellers are more supple after soaking. The treatment is also supposed to be good for glass or polyester filled nylon props.

Phil

If the props absorb water wouldn't affect the balance?

Jim

In principle it will absorb water evenly, so balance should be minimally affected.

Phil

Mark Boesen Wed Jul 03, 2013 11:07 am

....along those same lines, an old thought/theory/belief was that wooden props should be stored horizontally as storing vertical the moisture would migrate to the bottom.

I gotta wonder if that concept came from '1:1 scale' wood props

ian1954 Wed Jul 03, 2013 2:07 pm

Cox International wrote:There have actually been issues with those props as they are old Cox stock.

We test-bend each one and have about 25% failure rate. Only a few hundred left and we are getting new ones moulded.

Please identify yourself to us by email to support@coxengines.ca with perhaps either an order # or order date. We will then send replacement props.

Bernie,

I thank you for the offer and your exemplary service but these things happen and a $1.95 prop (£1.28) is of little consequence to me. You are also to be acknowledged for conceding these props lack of perfection and for testing them before you ship.

Buying "old things" is always a risk, not everything stands the test of time and things that spin at 5-30,000 revolutions per minute have to be treated with caution - new or old. It could happen with any propellor - just don't stand in line with the blades!

Thank you again.

Cox International Wed Jul 03, 2013 2:13 pm

Ian,

We really need to replace them, as we have done for others in the past, as they were evidently defective before we shipped and you can expect to receive non-defective merchandise.

We insist ... sunny

**RknRusty** Wed Jul 03, 2013 2:59 pm

Haha, Ian you're gonna get new props and by dang, you're gonna like it! And that's that. lol!

ian1954 Wed Jul 03, 2013 4:28 pm

I will drop a note with my next order!

"Oh yes you will, oh no I won't" - British pantomime sketch!

batjac Wed Jul 03, 2013 4:30 pm

Mark Boesen wrote:....along those same lines, an old thought/theory/belief was that wooden props should be stored horizontally as storing vertical the moisture would migrate to the bottom.

I gotta wonder if that concept came from '1:1 scale' wood props

I'm sure it did. On fulls size props, the moisture migration is a real issue. I always keep my prop horizontal when not flying, and store wooden props horizontal on the shelf. For model props, I wouldn't worry about it. The moisture content isn't that high, and migrating two to three inches is improbable unless the prop's been resting on one blade for 20-30 years. But, a 60" prop sitting vertical in changing weather is different.

The Aeronaut Mark

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