Safety upgrade of a Hollenbeck winch.

[Jurgen]

Hollenbeck, quite a name in winch country, but this winch was equipped with only one solenoid, a very big expensive Bosh 0333 006 004. Prices rating from 100 (Internet) till 150 euro (local dealer). I envy US guys for having Cole Hersee much cheaper at same specs.

Not only for peace of mind, but some regulations start to ask for 2 solenoids in series as a safety precaution against sticking contacts. This to the very disappointment of inquisitive persons of malicious delight who desperately want to witness an expensive moulded enchanting glider dragged and violently crashing on a turn around. Let them search other coasts, bye bye.

Having two solenoids operated by one and same footswitch might be the last attempt of the disasterfreaks to stay for awhile, as that switch has to empower 2 coils now. They can only hope for that one switch to fail with sticking contacts so all their perceverance get rewarded after all. To undermine their last aspirations I gonna use 2 switches operated by the pedal, each switch devoted to one solenoid. As mentioned before in RCgroups, the 2 switches not using in series because then you never see if one of them has sticking contacts.

Jurgen.

To be continued...........

[Jurgen]

While checking the working of the solenoids on a bench and appyling the 12volt with some probes to the coil-contacts, each time opening the circuit it draw a (little) spark . Not strange actualy because one interrupt a current (of 1 amp or just above) trough an inductive coil. I realised this sparking must happen also within the foot pedal switch, not healthy !

So i soldered a rectifying diode over each coil with the anode on "ground", see pict. Now the sparks where gone (or so little they cannot be seen or hurt anymore) when opening the circuit. This must please the footpedal switches. Only one side effect: when opening circuit the current trough the coil dies out over the diode instead of stopping immediately, as a result the solenoid stays ON for 1/4 to max 1/2 second longer than normal, not a big deal i guess. After this tiny delay I hope this is not slowing down the actual opening speed of the main contacts, any thoughts welcome.

[Jurgen]

Engaging / disengaging of the solenoids by foot switch was done in series by this little master switch. It flipped over to easily (especially during transport) and on a remote view one could not see whether it was in ON position or not. Had some key-switches lying around waiting to become useful, these will never flip over by accident and on remote view it clearly shows its state. Also now have the occasion to remove the key from the switch when going away from the winch for a while, and to loose the key accordingly :D. I have 3spare key's if that happens.

[D_Ryan]

P.M. sent...

r/
David

[rogerflies]

The later style Ford starter solenoids have a built-in diode to eliminate the arcing from the collapse of the magnetic field in the coil. The fact that it's used in a high production application tells me it doesn't cause problems with the contacts in the solenoid.

The solenoids I'm talking about look like this:
http://cgi.ebay.com/ebaymotors/Starter-Solenoid-for-1997-Ford-Explorer-New-in-the-box_W0QQcmdZViewItemQQcategoryZ33576QQihZ005QQitem Z150098164152QQrdZ1QQsspagenameZWDVW

I've used them on several winches with no problems. Hooking them up with the polarity reversed will burn up the diode, but the solenoid will still work.

Roger

[Jurgen]

David, i'll get back on your PM.

Roger, if there is an internal diode, then it would be very likely one of the 2 coil-contacts has an internal connection to the ground too or at least show a very clear PLUS and MINUS sign, just for not burning the diode. The picture is little small to see that. In case of the Bosh all contacts are non-connected with the ground.

I asked myself to place a diode over the major solenoid contacts (the motor is induction load too) to prevent them from sparks, but i guess they cannot handle the high currents involved. Initialy they should be able to withstand the motor current --> smelly burned expencive diode, stinky business.

Jurgen.

[rogerflies]

The way I understand it, the diode only conducts the current flowing opposite the normal flow, since the collapse of the magnetic field generates a current with the polarity opposite to the current that created the field.

I doubt the "collapse voltage" in the motor windings is large enough to worry about, since there aren't many turns in the coils. It's the high current trying to jump the contacts as they are opening that generates the heat that sometimes welds them together.

I like the idea of putting diodes on the foot-pedal switches, and using a hinge with the lever to operate the switches makes the pedal more compact. I'll keep those ideas in mind the next time I build a winch and foot-pedal.

I'm going to stick with the idea of sequential operation of the solenoids by having a delay between the switches in the foot-pedal.

Roger

[Miami Mike]

... the collapse of the magnetic field generates a current with the polarity opposite to the current that created the field.No. The collapse of the magnetic field generates a current in the same direction as the current that created the field. However, to do that it produces a voltage across the coil with the opposite polarity of the voltage that energized the coil.

For a good hydraulic analogy to an inductor, think of a water turbine with a flywheel connected to it. As water flows through the turbine, it causes the flywheel to spin, and if the water flow is stopped, the momentum of the flywheel will cause the turbine to continue spinning and pumping water in the same direction.

[Jurgen]

I think you both are simultaniously right by looking at another angle to the case.

It is indeed same direction when it comes to the current flow through the coil, before and after footswitch release.

It is also opposite polarity when it comes to voltage polarity over the coil contacts, that is why footswitch=engaged the diode is BLOCKING and after footswitch=open the diode is in FLOW.

Drink a beer together :D
Jurgen.

PS Miami M: i'm going to do the LED's too, comes later.

[Miami Mike]

I think you both are simultaniously right by looking at another angle to the case.What's the other angle? All you did was repeat what I wrote. :confused:

Anyway, don't forget the buzzer (http://www.vvsss.com/buzzer/).

[Jurgen]

No. The collapse of the magnetic field ......Just wanted to say there was no "No." Never mind.

The buzzer:
i hesistate abit using a buzzer because it will sound each time the solenoids are are opened with a delay in between, wouldn't it sound during this delay? I think the buzzer is fine when you let the solenoids open very simultaniously.

Jurgen.

[Jurgen]

First picture: original solenoid Bosh 0333 006 004 with angled contacts, price: ahumm: 147 euro.
Rated at 150 amps, not mentioned intermittent or continuous duty.
Automotive shop: "We don't fit anything bigger than this on any truck, you won't need any bigger in any application".

Don't you have anything less expensive?

"Yes we carry MonarkDiesel rated at 80amp, 40 euro."

Hmm, 80amps is little.
But if I use Rogerflies option to open this solenoid AFTER the original Bosh then it might do the job as well. So i bought it.

Spoke with a fellow worker about my upgrade and he says: "I have several solenoids lying around in the garage, I'll look for it".
He comes back with 2 giant Bosh 0333 009 004, very same specs as the original, only difference is aligned contacts (not angled) and i get them for free, what a great guy :D (no you won't get his name!). So no use for the Monark which go between the other junk lying around for later purpose, hopefully.

This makes me having a spare solenoid of the aligned-contact-sort, so it's good to have this one to open first and carry the burden of drawing the arc.
Life is good :)

[Miami Mike]

i hesistate abit using a buzzer because it will sound each time the solenoids are are opened with a delay in between, wouldn't it sound during this delay?Yes, it would. I'll see if I can come up with something.

[rogerflies]

I've made simple and inexpensive time delays by putting a capacitor across the coil of small relays. It doesn't take much of a capacitor to store enough energy to keep a small relay closed for a few seconds. Here's a circuit that will interrupt the power going to the buzzer to keep it from sounding when one solenoid closes before the other.

The circuit to the buzzer is wired through the normally closed contacts of a DPST relay and it is opened when power is applied to the first solenoid. The capacitor will hold the relay open for several seconds after the footswitch is released. The buzzer will then return to its normal operation.

You might not need the capacitor, though. The DPST relay by itself will disable the buzzer whenever the footswitch is being used.

Roger

[Miami Mike]

You're on the right track, but I think we need a circuit that delays the energizing of the buzzer until the energizing signal has been continuously active for at least a second or two. That could be a bit more complicated. Your capacitor will only keep the relay energized for a time after the energizing signal is removed, and I don't think that will stop the noise during a normal launch.

http://www.vvsss.com/buzzer/

[rogerflies]

The DPST relay shown in my sketch doesn't replace the relay in your buzzer circuit. It goes between your K1 relay contacts and the buzzer, and the coil is wired to the coil terminal on the first solenoid to close. Since the NC contacts on the DPST relay will open whenever the footswitch is being used, the buzzer will not sound off during a launch.

I think disabling the buzzer during the launch is a better solution to the problem than using a time delay.

I'd just forget about the capacitor. You don't need it to disable the buzzer, and you'd need a diode in series with it to keep the capacitor from discharging through the coil of the solenoid. I forgot to show the diode in the sketch I made.

Roger

[Miami Mike]

I get it now. Yes, that might work.

[Jurgen]

See the strip cartoon :)
Maybe the buzzer comes after all, we'll see.

[rogerflies]

Just curious....

Assume you have a single microswitch on your foot-pedal and your winch is equipped with the safety buzzer system. What will you do if the buzzer starts going off while you're pulsing the pedal during a launch?

Continue the launch in your normal manner?
Stop pulsing, let up on the pedal, and get the plane off the line ASAP?
Stop pulsing, but hold the pedal down, and go into the zoom mode?
Something else?

Roger

[Miami Mike]

Assume you have a single microswitch on your foot-pedal and your winch is equipped with the safety buzzer system. What will you do if the buzzer starts going off while you're pulsing the pedal during a launch?Continue the launch, but yell for someone to be ready to hit the safety cutoff switch or disconnect the battery if necessary.

You could even continue using the winch even if you don't have a replacement solenoid available, but with some extra caution, and with someone always ready to cut the power in case the other solenoid gets stuck too.

[Jurgen]

I plan to have a master switch on top of the battery which can be turned of by a (within pilot hand reach) string wire. If it works out picts will follow.

Build will stagnate for a week because not at home.
Jurgen. (Will be completely disconnected from any RC thing, I do hope to survive this)

[Tuomo]

I plan to have a master switch on top of the battery which can be turned of by a (within pilot hand reach) string wire.

Why not simply use quickly removable battery clamps?

(I think they were demanded by F3B rules since 2006?)

[Jurgen]

I just bought those clamps Tuomo, they're great & will be introduced later. I hope to combine them with another stupid simple split second fast current cut off system for any emergency.
Jurgen. (you see, i could not leave without checking RCgroups, i'm hooked :))

[Miami Mike]

What I've usually seen at contests is a battery clamp with a cord tied to it that the retriever operator can easily reach and yank.

[Jurgen]

David Ryan asked how the winch was build up, i better do this in the open to be inspiring for many more. I think Hollenbeck has a very nice strong simple approach for assembly. The electronice are nicely putted out of sight and accidents. I hate seeing alot of wires and contacts where my key-ring can fall on :)

The console is made out of one big piece of an unrustable plate.
The motor holder could be made of 5 pieces welded together.

Jurgen.

[Jurgen]

Shaft and drum.

[POF]

May I ask how often there has been a problem due to a single solenoid design? Haven't seen any myself but I have only been using a winch for a few years.

Peter

[rogerflies]

In assessing risk, you must ask two questions:

How LIKELY is it that something will happen?

How BAD will it be if it does happen?

Then you multiply those factors to get a value of the risk.

In this case, the answers are "not very likely" and "very, very bad". For most of us, that's sufficient justification to do something to make sure it won't happen, especially when it's pretty easy and inexpensive to reduce the likelihood to almost zero.

Roger

[Miami Mike]

May I ask how often there has been a problem due to a single solenoid design? Haven't seen any myself but I have only been using a winch for a few years.I probably haven't done nearly as much winch launching as most of the other guys here, but I personally watched our club's winch smash a glider to bits two years ago, when its single solenoid got stuck. We had two new solenoids the next week, and that was what inspired me to design my buzzer circuit. Other guys in our club have told me of other stuck solenoid incidents they've seen.

[Jurgen]

Possible the more powerful motors in US draw more current and might induce more risk this way. Nevertheless peace of mind is worth something, of course one can always depend on an extensive prey before each launch :)
Some regulations also go towards this, see picture, a part out of soaring digest magazine march 2007 page 10 (for F3B rules). I don't know if this is official yet.
Jurgen.

[rogerflies]

I notice the proposed regulation says "...hand operated pushbutton".

Is anyone really using a hand-operated switch to control their winch? What's it look like? How do you hold it while you're holding the transmitter and launching the plane?

Roger

[POF]

...but I personally watched our club's winch smash a glider to bits ...

Why a smashed glider? Are you not able to get of the line? Usually I step on the pedal all the way up (depending on the wind) and that is the same sitiation when a solenoid is stuck?

Sure - I understand the peace of mind argument.

[Miami Mike]

Why a smashed glider? Are you not able to get of (off) the line?In the case of the incident I saw, no he wasn't. Remember, it takes a certain amount of time to realize that something is terribly wrong, and then to figure out what to do about it. By then it's likely that either your wings have folded, your plane is a lawn dart, or both. I've also read references to planes being "strained through the turnaround". :D

[Jurgen]

Normal LED's are around 5 or 10 mCd (milicandela).
Powerled's go up to 2000 mCd.
I putted in 2 led's giving 18000 mCd each :cool:

They have now also 25000 mCd led's but were twice the price and not needed for the purpose. Mine have a 20° light angle, the more powerfull ones only few degrees. Bonus for wider angle in our case.

Jurgen.

[lesterpk]

That proposed rule did not pass at the CIAM meeting, the status quo remains.
Les.

[rogerflies]

I'm still curious about using hand-operated pushbuttons for the winch. I've seen them used by the person running the retriever, but never by the pilot launching the plane.

Roger