rogerflies

My Feedback: (3)

I've got the connection to the spline figured out. I just cut the splined section off the starter Bendix, trued it up, and put a plug in it to center it on the shaft. It will be pressed into one of the drum end plates, and secured with set screws.

I've decided to make this a F3B-style winch. What size should I make the drum? I'm thinking about 4.5" OD by 7" long with a 2" center. Would that work OK?

Roger

Toomanyplanes

That sounds good Roger. 2" works pretty good for drum ID for most winches. You might consider a longer drum if the cheeks are only 4.5". I would think you would want to put on about 400-600 yards of line. The Discus winch I built has a drum that is 9" wide with 5" cheek plates. I got 650 yards of 200# test Mono on that one with a drum ID of 1.9". Lots of combinations can work. Motor power and wind conditions can make a HUGE difference in what drum ID to use but 2" is a good starting point.

We should try to do a team project. Let me know if you are interested.

Tony

rogerflies

My Feedback: (3)

I looked at a bunch of F3B winch sites yesterday, and I saw a range of hub diameters from 1 5/8" to 2 3/8". Most of them seem to have the length arond 8". Unfortunately, they don't give the outer diameter of the end plates. Judging from the motor diameter, it looks like about 4 1/2" is the largest.

I think I will make the drum so it can be easily replaced with one having a different hub diameter. I plan on having a support bearing on the outer end, so it won't be a one-bolt swap like yours, though. Maybe three will do it. I'll start out with a 2" hub since I have the machining fixture for that size already.

The next step on the winch project is the one-way brake. I'll work on that for the next few days while the contractor guys are doing the floors in the house and the new finish is curing. Have to take the computer set-up apart for that, so I'll be off-line for the duration.

A joint effort on a winch would be interesting. I'm certainly open to new ideas, and it would be nice to have someone to look at things from a little different angle. Too bad we're so far away from each other.

I'm still concerned about how I'm going to test this winch. My only plane is an old Lovesong, and I hesitate to do dramatic F3B-style zooms with it. How will the chute come off the towhook if the line won't go slack? I sure don't want to break the plane.

Roger

Toomanyplanes

The drum diameters do vary a bit but usually they have some sort of clamshell arrangement to change drum diameters during the contest depending on wind conditions. If you are planning on running your 1.4 Kw Bosch starter on a fixed drum size, I would tend to err on the side of a larger drum, otherwise make a 1 5/8" drum and also make a couple of sets of PVC clamshells of differing diameters that you can increase the diameter of the drum if there is little or no wind. Experimentation is the key here. My winch has the replacable drums that can swap out with one bolt just incase the line gets FUBAR during a contest as well as differing diameters for the inner hub for wind conditions.

It would be really cool to have a one way clutch that would be self releasing but I never attempted it as it seemed overly complex. Yes, I have forgot to release the brake and had to walk back to the winch but that mistake is self critiqing !

I found a cheaper source for the one way bearings. Several sizes are available but I only have the 25mm ID ones right now. Sounds like you have something else in mind anyway.

I would be real careful with the Lovesong. It wasn't designed for the high G launches that come from a powerful winch. If you can get a stronger 3 meter plane that would be preferable. You can launch it carefully but be conservative.

Zooming is a technique used by guys at most contests to muscle out extra altitude from the plane by "loading up" the line with tension and diving the plane for speed at the end of the apogee with full throttle on the winch then pulling up to near vertical immediately in the high speed dive converting speed and inertia into altitude. There will be ALOT of tension on the line when the plane pulls up and some estimates of the G force on the plane is around 30 to 40 G's! The line will come off the towhook on it's own in the pull up. The plane is near vertical anyway.

Zooming is where most planes get into trouble. I have seen planes overrun the towline and get caught up in the tailfeathers (yipe!) or the plane starts loosing parts or aerodynamic flutter ensues due to the incredible speed and high angles of attack in the pull up.

Don't worry about the line coming off the plane. It will slide off when the plane pulls up. You could also treat it like a high start and simply let off on the power and let the drag of the line pull it off. Most towhooks made for winch launching are pretty stout and made from stainless. Most are only 1/2" to 3/4" long to allow the line to slip off with less leverage on the towhook. The backup in the fuselage is usually a piece of quality 1/4" Finland plywood as an anchor.

Towhook placement is critical as well. But that's another subject...