Hi Ulrich

Fairlead distance is more than adequate. We have no level wind mechanism
but the ratio of drum width to drum-to-guide rollers is such that the
cable winds smoothly. (It's 3.5m to 150mm or around 23:1.)
Guilotine design is also over engineered. We use the same design on our
"old" single drum, and test it regularly. The only problem we have
experienced is that the original arm to the weight that drives the
guilotine suffered metal fatigue from the vibration (especially from
towing over our rustic airfield). We substituted a more "springy" softer
steel and fitted a seperate hardened blade to cure the problem of the
lever breaking occasionally when we tested it. This only ever happened
after cutting the cable when the arm hit the stop, but still cause for
concern...

Thanks
Bruce

Ulrich Neumann wrote:

c1rrus wrote in message ...

One for the mechanically minded out there.

Our club is currently constructing a double drum winch. More accurately
I should say - re-constructing as said winch is based on, and uses the
major components of an old single drum winch.

The design is of the trailer with a V8 vehicle transmission attached type.
Ford 352W (2V) engine
3 Speed automatic transmission
Modified differential feeding power to drums attached to the half shafts.
Drums are steel units with the large base diameter and narrow aperture
suitable for our 2.75mm single strand medium carbon spring steel cable.

Having become involved in resurrecting the project after it's
originators left the club and the winch lay derelict for some years I am
not at all confident that the power transmission mechanism is safe,
durable or desirable.

Current design has a crude castellated gear (I would not glorify it to
refer to it as a dog clutch)
This slides from side to side so that it is completely disengaged in the
centre and engages one or the other half shaft when moved to either side.
There is an interconnected disk brake that locks the undriven half shaft.

One problem is that this leaves the diff spinning one way or the other
on every launch. Now Borg-Warner make a good product but I doubt the
engineers had his treatment in mind...
Another problem is the poorly supported axle to the drum.

There is no way we can afford a modern commercial winch, but this does
not mean we should not make a better attempt at out homebuilt. Would
appreciate the opportunity to learn from the experience out there. We
need input on transmission paths, materials, controls and probably many
things we have not thought of yet.

The engine and gearbox are standard , reliable and have been competently
overhauled. For the rest, the only decently engineered parts of the
project are the drums , which are solid, accurately made and balanced.
The rest would be very familiar to Messrs Heath and Robinson...

Any help gladly received.



Hi Cirrus,

I am in the process of investigating the different technical aspects
of building a winch. So far, I have several reports that indicate
using an axle - specially one from a commom pick-up truck - in the way
you described it, is a sure way of heading for a desaster. The
differential gear has to be locked out by welding the spider gears
solid. You can find references about this on the net. Keep in mind
that doing this will change the gear ratio. Your drums will most
likely spin slower at a given input shaft speed than with the
differential spinning. To keep the design simple, you may want to
consider just a single drum design.

To keep the cable from piling up on the center of the drum, keep the
distance between the fairlead and the drum as long as possible. German
regulations require a distance of at least 18 times the width of drum
between the drum and the fairlead to be operated without a level-wind
mechanism.
Do you have well functioning guilliotins capable of hacking through at
least two cables in one trial?

Happy winching,

Uli Neumann
Libelle 'GM'