How about this for recovering energy?

Same principle as a boost converter.

Or you could use a mosfet to make use of "synchronous rectification". Less lose of energy that way, a mosfet will drop less voltage than a diode.

 

I have a Logan too! It's a 1954 920. I bought it for $50.00 stripped. HS, TS, Carriage. All gears were missing, so it was converted to a wood turning lathe. I made a foot clutch/brake that works very well because flat belts clutch well.

I bought it way back in the early to mid 70's from a club member when I was a member of the Suffolk County Radio Club in LI N.Y. How the hell I lived through those winters escapes me!
Chris

I took the clutch off of mine and put a variable speed DC drive on it instead. Bought it at an auction and had to take it apart to get it out of a basement.

 

Does anyone have a good link to build threads for these solenoid engines?

I did quite a bit of searching to find this.. You owe me!
http://madmodder.net/index.php?topic=3874.0

The kicker is this was found in a Yahoo search, yet I'm a member of this group.. Duh!

 

Or you could use a mosfet to make use of "synchronous rectification". Less lose of energy that way, a mosfet will drop less voltage than a diode.

Synchronous rectification won't apply here I'm afraid. The idea is to get the current moving through the solenoid as quickly as possible, and stop it as quickly as possible (without burning up anything). The former is usually accomplished by increasing the supply voltage, and then an active current limiter can be used (aka "chopper driver", used with stepper motor control circuits). The current will be stopped most quickly if there is no current path, but the collapsing magnetic field can generate VERY high peak voltages; odds are that the insulation of something will be broken down by that, with eventual system failure.

Synchronous switching might be useful to "loop" the current to sustain a low-resistance solenoid (sort of like using a Corliss valve arrangement in the old steam engines) ... but to get the current to stop quickly without damage, one needs to use a voltage clamp.

 

I took the clutch off of mine and put a variable speed DC drive on it instead. Bought it at an auction and had to take it apart to get it out of a basement.

Actually, a foot clutch/brake is more useful for a woodturner because we're constantly stopping and starting to check the work. It also lets me do a soft start to prevent the faceplate from unscrewing when sanding in reverse. I really loath the sound of DC motors but they are torquers!

Chris

 

Synchronous rectification won't apply here I'm afraid. The idea is to get the current moving through the solenoid as quickly as possible, and stop it as quickly as possible (without burning up anything).

Sarge, you're bringing up a very good point here and it really begs the question of what these machinists are using for back EMF suppression. It seems to be an un-addressed issue by the modelers.

Chris

 

Chris,
From what I can see - they're not using anything. The fellow with the pot-adjust for the speed is using a TO-3 packaged transistor (likely a 2N3055 or MJ2955) so if they aren't using some kind of snubber or at least a diode, the transistor will get whacked in a pretty big hurry. Those are typically rated for Vceo=60v.

 

Hey, how fast are Transorbs? They're used across the 120VAC solenoid valve on my dishwasher. I see no reason that an AC solenoid can't be used. In fact the modeler in last link I posted built his engine using one. Come to think of it, a zero crossing detector could work... I think!

Chris

 

Transorbs are basically two Zeners back-to-back. They're available in lots of voltage and power ratings. I frankly don't know how fast they are offhand; I'm certain it would vary across the product line(s).

A zero-crossing detector wouldn't be much help.

 

CDRIVE- sorry, but no pictures; that was 73 years ago & about 23 moves. Your 3rd ref. 1910 flywheel motor is close but unknown to me at the time. I used the bells hinged armature & part of the tang, with U shaped shaft supports of tin can metal. --Bernard

 

Check out this one!
http://www.youtube.com/watch?v=GKqEzXAlzS8&feature=related
Brass, four solenoids laid out as a small aviation 4-banger engine.

 

Synchronous rectification won't apply here I'm afraid. The idea is to get the current moving through the solenoid as quickly as possible, and stop it as quickly as possible (without burning up anything).
...

Why on earth do you need to stop the current as soon as possible? These things run at a few Hz!

Once the points establish current (magnetic field) the best energy efficiency would be to maintain that coil current as long as possible after the points open (after it stops drawing battery power), so either a simple coil diode or synch rect is the best. The coil current is the motive force, so the longer that coil current is maintained for the same points duration the better the motor performs.

Thanks for the links too!