Reversing method?

[Arnak]

Hi Folks,

What I am attempting to make is a dog lead rewinder.

No, don't laugh...

Part of the mechanism needs to be able to automatically reverse at the end of a shaft.

The idea is to spool or unspool the lead using this mechanism so that the lead will roll up tidly on the spool.

This is required as the lead will be about 100mt long.

If you imagine an outlet eyelt travelling along a shaft then when it reaches then end reversing automatically as the lead is wound back in.
Thereby tidly winding the lead back onto the spool.

If that makes sense how do I go about building a reversing mechanism?

Any ideas / suggestion would be most welcome.

Thanks,

Arnak

[Tim Bayliss]

Go into a fishing tackle shop and examine a MULTIPLIER reel with a LEVEL WIND. It's exactly what you have described.
The shaft that shunts the level winding guide back & forth looks like a large pitch thread cut both ways.
You can also see this type of thread on a 'yankee screwdriver', the type you push down on to operate (before the advent of cordless drills!!).
Regards,
Tim

[Arnak]

Thanks Tim,

I have the very item in my tool box!

Arnak

[SteveW]

Arnak,

I spent a lot of years in Air Cadet Gliding, basically a 16 year cadet at either end of a 1000yd cable, one with a big engine the other in a fretwork fighter. In the heart of the noisy end was the scroll gear and it extended across the width of the drum.

The first choice is the topology ot the drum, wide or narrow. Wide NEEDS a scroll gear to distribute the cable evenly but the gear drive can be complex and a nightmare when it goes wrong.

A pair of us built a single narrow drum glider winch and it didn't use any scroll gear feed. I did ensure it had a deep rim.

Eventually the ATC updated us to a Dutch Winch. That used narrow drums and simple cams to deflect the feed left/right geared from the drum drive.

A fine left/right feed which can get very tricky at the ends, stack too much and it'll topple and trap the primary cable. Another way is to wave wind as per those cheap balls of string. This also makes the gearing to the scroll (which need only be a cam) but it has to be either a one-and-bit:one or just-less-than-one:one to get the wave wind around the core.

The bit everyone forgets is the paying out problem. If the pull stops and the drum doesn't then it's time to get intimate with all the oily/greasy bits . The simple approach is to apply a drag brake of some sort.

[Arnak]

Thanks for the info Steve.

I don't suppose you know of any drawings of the mechanism for the dutch winch anywhere do you?

The paying out mechanism will be simply by the dog pulling the lead out, soas you say a simple drag mechanism should suffice.

Regards,

Martin

[SteveW]

Arnak,

No drawings I'm afraid but...

If you can imagine a cocoa tin set on a shaft and then cut diagonally (avoiding the shaft) you're almost there. In the case of the Dutch winch ( a Van Gelder) a pin sat in the gap between the two cut ends of the 'cocoa' tin such that as the tin (really a cylinder) rotated it moved the peg and thence the cable feed shoot across the drum and back.

If you want to go the full distance you stick six drums on a shaft complete with scroll gear and add a bloody great Volvo diesel plus a torque converter on the end. Add a thousand yards of two ton cable to each drum and put the dog on the end. Not forgetting to paint the whole lot yellow.

[Arnak]

Hi Steve,

Thanks again for the info...

Err... I think I may need to get a bigger dog as I've only got a miniature poodle... ;D

Seriously, do you know how the peg is reversed once it reaches the rnd of the diagonal slot in the drum?

Regards,

Martin

[jackrae]

If you live anywhere near a fishing port _not many of those about nowadays - suggest you have a look at a trawler winch.

they almost all use a double helix (reversed) wire guide system to ensure the wire ropes spooled onto the drum correctly.

as the wire guide reached the end of a helix it was automatically knocked over onto the reverse helix

Old tech and works - and robust enough to stand waves, wind and old sea dogs

regards

jack

[SteveW]

Arnak,

The cam pushed one way during half (0..180 degrees) its rotation and then the other way as it continues to 360 degrees.

If this helps

|- ------------|
|-- -----------|
|---- ---------|xxxxxxxx
|----- --------| shaft
|------- ------|xxxxxxxx
|--------- ----|
|---------- ---|


Assume the above is a side view of the split cylinder note diagonal 'gap' which wraps up the other side. Rotate through 90d and you get:

|-------- -----|
|------- ------|
|------ -------|xxxxxxxx
|----- --------| shaft
|------- ------|xxxxxxxx
|-------- -----|
|--------- ----|

[Arnak]

Hi Folks,

Thanks very much to steve and Jack!

That should beall I need to build it....

Regards,

Arnak