changer scissor

[Scott Howard]

After the thread on material for changer levers ,
( viewtopic.php?f=12&t=27 ) I began to make a scissor to replace the double raise / lower on a MSA I am planning on putting together after the first of the year . Going to a Universal requires several stings to be triple raise . I have my first one finished . I am looking to make 4 for this guitar.

Below is a picture of the metal used from elecrical box covers available at the local Lowe's or hardware store . I needed the longer ones for the raise and could not find them without the center knock out. I am sure they probably make them but it wasn't worth the time to keep looking.

Also I used 1/4" Chicago screws and filed them to fit . The screw sticks out of the back side a bit and I am thinking I may brad the end of the screw to avoid it loosening up in the future.

Until now I would not have undertaken making these but it was not that hard and I will be adding them to most of my MSA's when I have them apart.

Thanks for the idea's

[burt]

Could I make a suggestion ?
If the base was made longer, it would allow for a longer return spring, which would make the lowers a lot easier to activate

[Scott Howard]

Burt
Note , taken and thanks . I was patterning after the MSA in the picture . I had seen you post elsewhere about a longer return spring would make easier lowers but was wondering how to do it.
I will draw some out and see what I come up with. My main concern when playing a Universal is the lowering the E's . With my hip and leg problems the easier the better.
I have seen ones like your drawing but not sure what make. Was it Sho Bud ?
Scott

[Scott Howard]

Here is a example of one like it . Back to the drawing board !

http://julianwinston.com/music/the_kline_guitar.php

[Scott Howard]

Version 2 is now done. Now I will end up making 12 to have matching ones.

[Bent]

A footnote and question to the longer spring idea.
-The spring has to be strong enough to hold the lower bar back when activating a raise.(and then some)
Richard, If I remember correctly what you told me about short vs long spring in England, the longer spring of same wire material and thickness will be weaker than the short one (not as many lbs of pull). Is this correct?

Maybe you also would be so kind as to tell us all about springs like the way you told me.
Also, your recommendations as to wire thickness, and tension needed for the different springs.
Thanks

[burt]

Bent,
Try this experiment.
Get yourself one of these

[burt]

Now, get one lower return spring.

Put one end of the lower return spring in the vice.

Hook the other end to the spring balance device.

Pull the spring balance until yoe get a known weight (say 20 pounds)

Whilst holding it at 20 pounds, measure the length of the spring.

Pull the spring balance until the spring is 1/2" longer, and take a note of the reading on the balance.

Now release everything, and hook four or five springs together.

Do the same experiment again (pulling to get 20 pounds etc) and you will notice that there is a marked decrease in weight required to increase the length by 1/2"

[Georg]

The advantage of the longer springs is clear, but I have noticed one slight disadvantage with having the spring hooked up that far back on the lower-scissor.

If the spring isn't aligned perfectly a twisting force will increase friction and wear and tear, as the raise and lower scissors will either be twisted/forced towards each other or the lower is forced towards the slot-side of the guide-plate.


The spring hook-up extension can be bended slightly to either side so the friction caused by twisting is minimized. Best adjusted while testing raise/lower action since the pulls themselves cause twisting.

A hard-steel guide-plate with deep slots with just the right width - 3/10 millimeter or so too wide for the scissors, and with rounded edges, that steady the scissors all the way back, will of course also help minimize twisting and friction.

[Scott Howard]

Georg
I had run into the twisting before and made a plate . I made them out of aluminum . What is the advantage of steel other than the fact it would wear less and last longer ?