Thumbwheels

[Mr. Loar]

Why are the thumbwheels in a bridge so dang hard to turn?

[Bill Snyder]

Take the pressure off of the strings and they should turn easily. http://www.mandolincafe.net/iB_html/non-cgi/emoticons/tounge.gif

[Eric W]

Well, if you haven't loosened the strings you're working against 100+ lbs of string tension. If the strings have been loosened and you're still having trouble you may need to check the threads for damage or rust, etc.

[AlanN]

There is nothing worse than inspecting thumb wheels and seeing evidence of tension rotation. Yuck!

[Red Henry]

The thumbwheels will often have a bit of corrosion or dirt on them or the screws, and that plus all the string tension can make them impossible to turn. Also, if a thumbwheel happens to be all the way down against the bridge base, it can be REALLY stuck there, requiring special techniques to start it turning even with all the string tension off (my favorite is pliers around a little piece of soft leather).

If you raise the bridge with full string tension on, you may also be increasing the string tension itself to a significant extent. But it's easy enough to let down the tension for a minute.

Red

[sunburst]

Well, if you haven't loosened the strings you're working against 100+ lbs of string tension.
While adjusting bridges under full string pressure is not a good idea, it's really not as extreme as that.
You're actually working against string pressure, not tension. It's the pressure that the strings put on the bridge as they are deflected from straight as they bend over the top of the bridge. At "normal" bridge heights and with "normal" string gauges, that pressure is somewhere around 50 to 60 pounds, and that's supported by two adjusters, so you're really only working against 25 or 30 pounds.

[mandroid]

-with loosened string tension to make less friction pressure
on the thumbwheels,

A Surgeons clamp that happens to have matching teeth
to engage the knurling on the thumbwheel,
gives me a good grip on the wheel.

[also (like needlenose pliers) helps get strings off the post if I've locked them in good]

http://www.mandolincafe.net/iB_html/non-cgi/emoticons/coffee.gif

[Dan Cohen]

Which way do you turn the wheel to raise the bridge?

[Jim Broyles]

Well, Dan, you need to raise the wheels just like unscrewing a nut off a bolt, so to get the wheels higher on the posts, you have to turn them counterclockwise. Lefty-loosey, in other words.

[Red Henry]

Also be aware that when adjusting bridges under full string pressure, it's possible to strip those fine threads in the screw-posts...

(Q.E.D.) (Translation: "It's been done.")

Red.

[J.Albert]

What I'd like to see are hex nuts made to match the thumbwheels in weight. They'd be much easier to adjust. If they were of the same weight and material as the thumbwheels, I doubt they'd have much affect on the sound of the bridge, if anything at all. I'm guessing the reason the "thumbwheel" remains as it is, is "slavery to tradition".

Doesn't Weber use a "hex" design on their "traditionally-styled" Brekke bridges?

- John

[Red Henry]

Years ago I substituted hex nuts on a bridge, for ease of adjustment, and found no difference in the sound. Many manufacturers now seem to provide larger thumbscrews than on Gibson's original bridges, however, and that can mute the bridge a bit.

I have heard that the Brekke bridges adjust with Allen screws-- "female hex," if you like.

"Slavery to tradition"-- or just inertia, or not thinking about it-- seems to be what keeps the mandolin world using, not only the thumbscrews, but the two-piece adjustable bridges themselves!

Red.

[Michael Lewis]

One main consideration as to the size and configuration of the thumb wheels is weight. We try to keep weight down in this area. Many years ago I used hex nuts for my bridges, and they looked rather klunky and were heavier than the smaller thumb wheels.

I use a slim tapered wedge of hard wood to push between the foot and the saddle to take tension off the screw adjusters. This way the thumb wheels turn very easily and no damage to the delicate threads. Best to be very careful when doing this.

[AlanN]

I have heard of that technique to raise the saddle with a fulcrum. I have never tried it and will heed Michael's advice. If I need to raise or lower the bridge top, I will continue to tune down first, then finger turn the wheels.

[Bill Snyder]

...I have heard that the Brekke bridges adjust with Allen screws-- "female hex," if you like.
Red there are two types of Brekke bridge. One that maintains wood contact from saddle to base and uses an Allen wrench for adjustment. Then there is the "traditional" Brekke that is similar to the more common adjustable bridges. The thumbwheels on it can be adjusted with a thin, 5/16 open end wrench.

[Red Henry]

Oh, okay. I guess that if I have seen one, I didn't notice the difference between it and an ordinary bridge.

Red

[VernBrekke]

Bill is correct. We have two styles of bridges. The traditional bridge nuts are knurled on one half and a 5/16 nut on the other half. We supply a small 5/16 inch wrench with the bridge.

Thanks,
Vern Brekke
Sound To Earth, Ltd.

[sunburst]

Vern, I assume you mirror-imaged that drawing to save time. The nuts don't really have opposite threads do they?

[VernBrekke]

Thanks John, the threads should go in the same direction. I'll change the drawing on our web site.

The drawing was done quite awhile ago and I probably did just mirror image the threads without thinking about it.

Vern