TubeNet

Fairly straightforward: you need to [carefully] de-tension the spring after removing the long screw which holds the rotors in the rack [one at a time, if you can].Then you cut off a short portion and rebend the retaining end, thread it up again and try it for tension. Biggest problem is if the spring is cut too short [as mine was last time], the tension will not be heavy enough and you will have to start over with a new spring.
In short---let a tech handle it; it's not very expensive and you will be happy not to have to get everything back into it's rightful place!

I remember reading that strong springs mean faster valves, so you may not get so quick action with weakened springs

tuben wrote:So I pulled the much loved, and much ignored Bell model out lately and was immediately struck by how STRONG the valve springs are by comparison to the Alex.... So much so that I'm going to give the horn a bath to be sure the valves themselves are not gunky... I do remember the valves being strong, but WOW....

The question is, can one reduce the strength of these springs or is that something best left to a repair craftsman?

RC

It's super easy. Hopefully you will be dismantling the rotors and cleaning them as well.

Basically, take a needle nose pliers and bend both ends of the spring up a bit so it coils just a bit more.

I reduced the tension on my Miraphone by disassembling the rotor linkage and reassembling it with one less turn. It may be that the open-wire spring is already as loose at it gets, and if you unwind it a turn it becomes slack. If that's the case, you can bend it around, I supposed, but you can also replace it.

Generally, the force required is the result of the length of the spring (more coils is longer, and longer springs are weaker), the diameter of the wire (heavier wire is stiffer), and the preload. Bending the spring ends so that they have to be wound up less, or unwinding them a turn, reduces the preload. There's nothing you an do about the length or the wire diameter short of getting different springs. Making the spring shorter, however, will make it stiffer, because the force will be distributed over less length.

Rick "who also likes fairly light springs" Denney

Rick Denney wrote:
Generally, the force required is the result of the length of the spring (more coils is longer, and longer springs are weaker), the diameter of the wire (heavier wire is stiffer), and the preload. Bending the spring ends so that they have to be wound up less, or unwinding them a turn, reduces the preload. There's nothing you an do about the length or the wire diameter short of getting different springs. Making the spring shorter, however, will make it stiffer, because the force will be distributed over less length.

Rick "who also likes fairly light springs" Denney

Whoa, Rick! I am not the engineer in this discussion, so take it slower please. When the tech adjusted my 1st spring, he removed 1 or 2 winds[?] because I felt the tension was a little too much for my newly surgically-repaired hand. This resulted in an action that is too slow after I worked it a little after leaving the shop. I have also grown stronger in the past 6 months, I suppose, and this is another factor.
If I correctly read what you wrote, the tech, by removing some of the length of the winding, should have made it a stronger/ harder action.But, it is much too slow, instead.What gives? Should I cut some more off or make it longer somehow?
Confused!
ScottW

You can INCREASE the pre-load on a rotor spring by PULLING the free end and wrapping it over the paddle bar. You can also INCREASE the pre-load on a rotor spring by taking it another wrap around the paddle shaft. You DECREASE the pre-load a bit by PUSHING the free end of the spring so that it generates a bit larger wrap around the paddle shaft. Depending on how the free ends are trimmed, sometimes it's possible to slip the end sideways over the paddle bar so one leg of the spring goes completely slack. If the spring is now too loose, you can PULL the free end a bit to increase the tension a little until it feels 'right'.

When trying to explain the dynamics of rotary valve springs, the terminology is a little confusing. The number of wraps is meant to be FREE wraps when the spring is in a no-load condition. More free wraps makes for a lighter spring as does lighter gage wire. Pre-load is the additional wrap that is applied to add tension to the paddle.

scottw wrote:When the tech adjusted my 1st spring, he removed 1 or 2 winds[?] because I felt the tension was a little too much for my newly surgically-repaired hand.

We're saying the same thing (Dan, too). My statement referred to the number of coils when the spring is unloaded. The longer the wire used to make the spring, the less tight the spring will be relative to unloaded.

But we don't use it unloaded. We wind that sucker up. On my Miraphone, my springs are at the minimum amount of winding necessary to avoid being slack. I also had to let the spring unwind a turn or two to get them to that point--they had been wound tighter. That doesn't change the length of the wire, that changes the preload on the spring.

The reason we coil a spring is because it makes a more convenient package than a straight piece of wire.

Rick "who used to cut off coils of car springs to 1.) lower and 2.) stiffen the suspension" Denney

If you are careful, you can easily de-tension the springs without disassembly. I have done it (and raised the tesion as well) or multiple rotary horns. All you need is a set of needle-nosed pliers (if you have bent-jaw needle-nosed pliers, all the better). You can grasp the end of the spring that rests against the stop bar and manipulate it so that it will move around the stop bar and de-tension itself by one turn. If they are still too stiff, repeat the operation on the opposite side of each spring.

So, let me recap: I want a little bit more tension [thus, stiffer paddle action], so I need to pull the ends of the spring out a little more and re-bend them under the retaining bar? This will mean there is more bent wire under the bar. Do I have it correctly?