Anyone had a winch drum failure?

We're making a new winch drum. The flanges on our drum bent out a little when moving from steel to Spectra line.

I'd like to know the dimensions and structure of any drums/flanges that have failed, or shown signs of failing, and with what length and type of line. Please pass this on to anyone who has details on that.

Bret

On Thursday, December 31, 2015 at 11:05:34 AM UTC-5, Bret Hess wrote:
We're making a new winch drum. The flanges on our drum bent out a little when moving from steel to Spectra line.

I'd like to know the dimensions and structure of any drums/flanges that have failed, or shown signs of failing, and with what length and type of line. Please pass this on to anyone who has details on that.

Bret

Bret,
check/join the winchdesign forum. This is a serious issue and it has been discussed in detail on the forum. There is also a great article in a past Soaring written by Scott Fletcher, member of Carolina Soaring, about building the current drum for our winch. There is a lot of engineering and fabrication knowledge that goes into building a winch drum, so it is a task not to be tackled by your average weekend warrior.
Uli
Winchmeister of Carolina Soaring

On Thursday, December 31, 2015 at 11:05:34 AM UTC-5, Bret Hess wrote:
We're making a new winch drum. The flanges on our drum bent out a little when moving from steel to Spectra line.

I'd like to know the dimensions and structure of any drums/flanges that have failed, or shown signs of failing, and with what length and type of line. Please pass this on to anyone who has details on that.

Bret

On Thu, 31 Dec 2015 08:05:31 -0800, Bret Hess wrote:

We're making a new winch drum. The flanges on our drum bent out a
little when moving from steel to Spectra line.

How do you wind the line in before putting the winch away?

Once flying has stopped we always pull the lines out to the launch point
and then wind them in relatively slowly with no load on them apart from
the parachute dragging on the ground and/or inflated and skating along
the grass before putting the winch away. This is recommended by
Skylaunch.

If you simply put the winch away after the last launch(es) the line will
be quite tightly wound on the drum(s) and may crush them as the night
gets cold.

Spectra rope has a fairly high coefficient of expansion (much higher than
that of steel cable) and this procedure leaves the rope loose enough that
it won't crush the drums when things cool off during the night.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

On Thursday, December 31, 2015 at 11:05:34 AM UTC-5, Bret Hess wrote:
We're making a new winch drum. The flanges on our drum bent out a little when moving from steel to Spectra line.

I'd like to know the dimensions and structure of any drums/flanges that have failed, or shown signs of failing, and with what length and type of line. Please pass this on to anyone who has details on that.

Bret

Scott Fletcher at Carolina Soaring is an expert on tis topic.
UH

Bret,
You betcha, had three fail.

The first was plate welded to a steel automotive rim. That one didn't stand a chance.

The second failed when they wound the steel cable on it under tension while hot, and then put it away. The cable cooled down, and crushed the drum overnight.

The third one failed due to lack of penetration on the welds.

Wrote an article for Soaring about Drum #4. It's not going to fail, got a little carried away with the design, and fabrication of that one.

Drum design in our case was highly constrained by the winch design. Second factor is that the forces acting on the drum are way more than you think they should be. Third factor is that Spectra under pressure on the drum flows like a liquid to some degree and this does some really interesting things to the side wall forces. Steel cable is somewhat self supporting which is why you had trouble after switching to spectra.

The winch design group is a great place to start. You can get in touch with me directly and I'll see what I can do to help. Drum #4 will be on our winch on the floor of the 2016 SSA convention in Greenville, SC.

SF

Thanks, I'm joining the winch design forum.

SF, I do remember reading your article, but before I was into the problem. I'll look that up.

On Thursday, December 31, 2015 at 10:05:34 AM UTC-6, Bret Hess wrote:
We're making a new winch drum. The flanges on our drum bent out a little when moving from steel to Spectra line.

I'd like to know the dimensions and structure of any drums/flanges that have failed, or shown signs of failing, and with what length and type of line. Please pass this on to anyone who has details on that.

Bret

The only people who have ever had a winch drum fail a Pretty much everyone who ever made a winch drum.

Joining the winch design Yahoo group is a great idea as is talking with Scott Fletcher and Uli Neumann.

On Thursday, December 31, 2015 at 8:05:34 AM UTC-8, Bret Hess wrote:
We're making a new winch drum. The flanges on our drum bent out a little when moving from steel to Spectra line.

I'd like to know the dimensions and structure of any drums/flanges that have failed, or shown signs of failing, and with what length and type of line. Please pass this on to anyone who has details on that.

Bret

Hi Bret,

I did a design for a drum to carry spectra line. it was built but never tested. I did a fair amount of FEM on the design. I would be happy to share it with you if you mail me off list: matt (at) digital shorts (dot) com

Matt Herron

Could someone send me the email of the winch design group admin? My request to join has so far gone unanswered. bret dot hess at gmail.