Electric Winch Project

On Saturday, September 8, 2018 at 8:13:44 PM UTC-6, Charlie Quebec wrote:
It is much easier to measure and control the line tension with an electric motor, eliminating the rocket launch a single seater can get when the winch driver has been
launching the training two seater all day. On my first flight in a Hornet on the winch, the acceleration was so great I could not prevent the glider from rotating immediately
with full forward stick, 5 terrifying seconds....

Charlie, I just added a PDF "Project Overview" document to the web page which goes to some length explaining the control system. As in the OP, the page can be seen at www.hdelectriclaunch.com

I saw make electric winches and put huge wind turbines next to them to recharge the batteries. The rule is simple, if you can land through the blades the launch is free.

On Monday, September 10, 2018 at 2:35:03 AM UTC-6, wrote:
I saw make electric winches and put huge wind turbines next to them to recharge the batteries. The rule is simple, if you can land through the blades the launch is free.

Free? How much did the winch cost? And did the wind turbine sprout from a magic bean?

On Monday, September 10, 2018 at 12:23:26 PM UTC+2, wrote:
On Monday, September 10, 2018 at 2:35:03 AM UTC-6, wrote:
I say make electric winches and put huge wind turbines next to them to recharge the batteries. The rule is simple, if you can land through the blades the launch is free.

Free? How much did the winch cost? And did the wind turbine sprout from a magic bean?

It is considered good practice to read all sentences in a post before responding.

On Mon, 10 Sep 2018 01:35:01 -0700, flybd5 wrote:

I saw make electric winches and put huge wind turbines next to them to
recharge the batteries.

Actually, the turbine would be fairly small.

A winch launch takes about 35 seconds from first movement until release
and about the maximum launch rate achievable with a two drum winch is 20
an hour[*], so the winch duty cycle is 20% at the most. If we assume the
winch burns a continuous 300kW during a launch (yes, that's probably a
large overestimate), then the average draw over an hour is 60kW - well
within the capability of a diesel trailer generator or a 22m diameter
three-blade wind turbine.

If the winch averages half power over the whole launch and the launch
rate is a more typical 10 an hour, the average power requirement drops to
15kW or a 9m diameter three-blade turbine.

The rule is simple, if you can land through the blades the launch
is free.

.... but an glider bigger than about 5m span would not fit through the
blades of a suitable turbine, even if it was stationary.

[1] Several years ago a bunch of us made periodic attempts to see how
high a launch rate was possible with a two drum diesel winch (Supacat).
We could hit 20 launches an hour, but never managed to exceed it, and
apart from the winch driver and launch marshal, we needed a full-time
driver in the cable retrieval truck, and another two people to collect
gliders as they landed, put them back on the dual launch queues, and keep
the launch queues moved up to the launch point. It didn't need much to
drop the rate either - an instructor who briefed when he and his student
reached the front of the queue, rather than one or two launches earlier
would do it.


--
Martin | martin at
Gregorie | gregorie dot org

On Monday, September 10, 2018 at 6:21:06 AM UTC-6, Martin Gregorie wrote:
On Mon, 10 Sep 2018 01:35:01 -0700, flybd5 wrote:

I saw make electric winches and put huge wind turbines next to them to
recharge the batteries.

Actually, the turbine would be fairly small.

A winch launch takes about 35 seconds from first movement until release
and about the maximum launch rate achievable with a two drum winch is 20
an hour[*], so the winch duty cycle is 20% at the most. If we assume the
winch burns a continuous 300kW during a launch (yes, that's probably a
large overestimate), then the average draw over an hour is 60kW - well
within the capability of a diesel trailer generator or a 22m diameter
three-blade wind turbine.

If the winch averages half power over the whole launch and the launch
rate is a more typical 10 an hour, the average power requirement drops to
15kW or a 9m diameter three-blade turbine.

The rule is simple, if you can land through the blades the launch
is free.

... but an glider bigger than about 5m span would not fit through the
blades of a suitable turbine, even if it was stationary.

[1] Several years ago a bunch of us made periodic attempts to see how
high a launch rate was possible with a two drum diesel winch (Supacat).
We could hit 20 launches an hour, but never managed to exceed it, and
apart from the winch driver and launch marshal, we needed a full-time
driver in the cable retrieval truck, and another two people to collect
gliders as they landed, put them back on the dual launch queues, and keep
the launch queues moved up to the launch point. It didn't need much to
drop the rate either - an instructor who briefed when he and his student
reached the front of the queue, rather than one or two launches earlier
would do it.


--
Martin | martin at
Gregorie | gregorie dot org

The numbers are simpler if one uses 1 - 2 kWh per launch (depends on glider weight and height of release) so 20 launches an hour would need a continuous 20 - 40 kW supply to maintain a steady-state battery charge. With a battery buffer, this supply can be very unsteady. The max power demand is not as important as long as the battery can deliver it.

40 kW is well within the range of various renewable sources. The incredible drop in solar panel prices make that a reasonable possibility. I estimate it would take about 2,500 sq. ft of them (~$25,000). One can imagine an accordion package which could be spread out on the ground near the winch.

While on the subject of dropping prices, Battery costs are dropping so fast that one can imagine a pack large enough for a whole day's winching. Recharging overnight from grid power simplifies the whole idea of an electric winch. Further imagine the winch mounted on an electric truck using the truck's enormous battery pack.

Thanks, Dan. The guiding idea was simplicity but simplicity is a slippery thing. High levels of functionality often demand complexity. Einstein got it right when he said a thing should be as simple as possible - but no simpler.

On Monday, September 10, 2018 at 11:28:42 AM UTC-6, Dan Marotta wrote:
I read your PDF on construction and operation of the winch.Â* And, though
I'm an electrical and systems engineer, I'm really fascinated with the
mechanical stuff and the design.Â* I thought it was very well done.

On 9/10/2018 8:57 AM, wrote:
On Monday, September 10, 2018 at 6:21:06 AM UTC-6, Martin Gregorie wrote:
On Mon, 10 Sep 2018 01:35:01 -0700, flybd5 wrote:

I saw make electric winches and put huge wind turbines next to them to
recharge the batteries.

Actually, the turbine would be fairly small.

A winch launch takes about 35 seconds from first movement until release
and about the maximum launch rate achievable with a two drum winch is 20
an hour[*], so the winch duty cycle is 20% at the most. If we assume the
winch burns a continuous 300kW during a launch (yes, that's probably a
large overestimate), then the average draw over an hour is 60kW - well
within the capability of a diesel trailer generator or a 22m diameter
three-blade wind turbine.

If the winch averages half power over the whole launch and the launch
rate is a more typical 10 an hour, the average power requirement drops to
15kW or a 9m diameter three-blade turbine.

The rule is simple, if you can land through the blades the launch
is free.

... but an glider bigger than about 5m span would not fit through the
blades of a suitable turbine, even if it was stationary.

[1] Several years ago a bunch of us made periodic attempts to see how
high a launch rate was possible with a two drum diesel winch (Supacat)..
We could hit 20 launches an hour, but never managed to exceed it, and
apart from the winch driver and launch marshal, we needed a full-time
driver in the cable retrieval truck, and another two people to collect
gliders as they landed, put them back on the dual launch queues, and keep
the launch queues moved up to the launch point. It didn't need much to
drop the rate either - an instructor who briefed when he and his student
reached the front of the queue, rather than one or two launches earlier
would do it.


--
Martin | martin at
Gregorie | gregorie dot org
The numbers are simpler if one uses 1 - 2 kWh per launch (depends on glider weight and height of release) so 20 launches an hour would need a continuous 20 - 40 kW supply to maintain a steady-state battery charge. With a battery buffer, this supply can be very unsteady. The max power demand is not as important as long as the battery can deliver it.

40 kW is well within the range of various renewable sources. The incredible drop in solar panel prices make that a reasonable possibility. I estimate it would take about 2,500 sq. ft of them (~$25,000). One can imagine an accordion package which could be spread out on the ground near the winch.

While on the subject of dropping prices, Battery costs are dropping so fast that one can imagine a pack large enough for a whole day's winching. Recharging overnight from grid power simplifies the whole idea of an electric winch. Further imagine the winch mounted on an electric truck using the truck's enormous battery pack.

--
Dan, 5J

I think that clubs in the USA that make a commitment to winching are on the right track.

My club seems close to having the critical mass of aspiring pilots in their teens and 20's. They would turn out and fly more often if the cost of launching were lower. Yesterday one of them brought up the cost of a 'decent glider' and he was wondering aloud if he would ever be able to afford one (probably yes, especially with the trend in resale prices). But at this point in his training, the cost of aerotows is (obviously) holding him back, and his situation is typical. We have a nice stable of club gliders and great soaring terrain, but aerotows are still pricey for many.