Saggy Tilt Locks (Strand Prelude)

[kgallen]

25+ years too late I realise...

I've used all of my Source 4s in the rig in my current show and need some more profiles so some of my Strand Prelude 22/40s need to come out to play for the first time in a while.

They are otherwise well maintained and looked after but I recall the last time I used some I had an issue with them sagging over time, even though their tilt locks were adequately tightened. Have any of our more "experienced" members got any good tips for helping avoiding the sagging. I'm most interested in "proper" maintenance tasks that can help, rather than stringing them up with some stiff wire.

For example if I remove the clamp discs and rub them down, would that help? The discs are otherwise in good condition - in the correct shape, not bent etc, and the clamping handwheel is the correct original Strand one and the washer is in place over the bolt head which is what clamps to the tilt disc affixed to the lantern body.

Thanks in advance for any ideas, and I hope you gain some satisfaction from going down "memory lane" a little!

Kevin

[sandall]

Back in the day I stopped using Prelude profiles over audience after several cases of Sudden Prelude Droop, often accompanied by Sudden Prelude Lamptray Unlatch, producing a Sudden Audience Toplighting effect.

[Don Allen]

That doesn't sound right. The head of the coach head bolt normally is the friction brake making contact with the tilt disk. If you are using a washer between the coach head bolt and the tilt disk, make sure it has good clearance with the square head shaft of the coach head bolt. I use a square file to open up the round hole of a washer if I am adding a washer. I don't have an exploded picture of a Prelude but the Patt23 is similar.

Did a bit more research and found https://www.theatrecrafts.com/bhc/equipment/strand-prelude exploded view diagrams for Prelude on Theatrecrafts website, so ignore my comments above.

patt23_explode1.pdf

[kgallen]

Thanks Don. Maybe I have misrepresented the existence of the washer - and I agree with you that the coach head bolt should be the friction brake. So I will make that check on the lanterns to ensure there isn't a washer in place: so thanks very much for the comment in that respect and the diagram for the Patt23.

[kgallen]

On 10/17/2022 at 3:29 PM, Don Allen said:

That doesn't sound right. The head of the coach head bolt normally is the friction brake making contact with the tilt disk.

Confirmed - it's handle-plain washer-yoke-friction disc-coach bolt head. No washer on the head side as I incorrectly said at the start.

Rigging tomorrow, I'll see how we go with sagging - although I think it's more of an issue when the lanterns have warmed up!

[Don Allen]

Would a split washer help ?

[kgallen]

20 minutes ago, Don Allen said:

Would a split washer help ?

Interesting thought Don, that had crossed my mind too when inspecting the washer position the other day. I think I might chuck one on under the handle and see how it goes (wonder whether I should add another plain washer too, as the handle is a Bakelite-type hard plastic).

Thanks!

[themadhippy]

Ah memorys of a safety chain through the back handle and round the bar to keep the dam  things from drooping

Edited October 19, 2022 by themadhippy

[sandall]

6 hours ago, kgallen said:

I think it's more of an issue when the lanterns have warmed up!

Yup, usually halfway through the first half🙁

[kgallen]

15 minutes ago, sandall said:

Yup, usually halfway through the first half🙁

Indeed I think the last time I used one, the moon gobo experienced a "sinking effect".

Guess what I need to use a Prelude for this time...

[Richard Bunting]

If memory serves me correctly, it's possible to alter the position of the yoke along its channel (within the extruded side of the body) and therefore the centre of gravity. This might help adjust for any drooping? just a thought.

[kgallen]

21 minutes ago, Richard Bunting said:

If memory serves me correctly, it's possible to alter the position of the yoke along its channel (within the extruded side of the body) and therefore the centre of gravity.

Thanks, yes you probably can. It’s in the most forward position it can be but that is still behind what is probably the COG of the lantern - and it’s a 28/40; the 11/30 must be even worse!!

[Junior8]

The odd 23 would sag a bit but nothing like a Prelude. The problem it always seemed to me was probably differential expansion between the components due to manufacturing variation. I'd try adding the spring washer or varying the position of the tilting fork if that is possible  as suggested. When you look at the exploded diagram you can see why it happens - it's a dire design.

Edited October 19, 2022 by Junior8

[indyld]

A spare safety chain was generally deployed to keep the end of those pesky 16/30 peckers up. 

[alistermorton]

The only preludes of ours that drooped were indeed the 16/30 variant.