Robertson's extension leather pad issue

CPike · #1 02-15-2011, 01:26 PM

I am working on a friend's bass with a Robertson's extension. She was complaining about it rattling on the E and Eb stopped notes. Both of these capos work their way loose when playing those notes loudly. This does not happen with the D and Db capos.

Examining the fit of the capos vis a vis the contact point on the string, I noticed that I could make the E and Eb capos slowly unclamp themselves with just the tiniest bit of pressure from my fingers. The fit of the D and Db capos were very different - they stayed put, with a little "pop" sensation occurring when disengaged. After fiddling with the capo tension and height (which solved nothing), I noticed that the leather pads on the unproblematic D and Db stoppers were much drier and harder than the soft leather on the E and Eb stoppers. They appeared to be very different types of leather.

My question is this: Have any of you experienced this on any chromatic extension? Is there a certain type of leather that will produce a more secure connection than others?

Chris

eerbrev · #2 02-15-2011, 06:00 PM

it may also have something to do with the amount to which each capo is used, the E capo gets used the most, considering it must be moved for any other note to be accessed.

The leather's suppleness may also be an indicator though, as you say. it may be possible to add another layer of leather on top (some of the guys in my studio do that.)

eerbrev

CPike · #3 02-15-2011, 09:57 PM

That's a very good point, although I don't think it's relevant in this case, as my friend barely uses her extension at all since she's had it.

Just as an aside, though, on my bass the E capo gets very little use - that's because I keep it open and stopped at D most of the time.

cdp

Heifetzbass · #4 02-16-2011, 04:06 AM

On my own extension, I just add a small piece of leather to the existing leather when it gets worn and doesn't stop the way I like. (It gets compressed after a year or so.) I buy the leather at a hobby store and attach it to the previous leather with superglue.

BG

robobass · #5 02-16-2011, 06:00 AM

Leather which is too soft could indeed be the culprit, but have you compared the forward angle of the stops? I think this is the biggest issue in making a latch which stays closed properly. I'm not sure exactly why, but I find that slightly more rake is desirable for the E and Eb, and slightly less for the D and Db. Going back to the leather, you could harden it up a bit by dabbing on some very watery hide glue. Have you or your friend talked to Robertson's about this? I'm sure they would be very proactive in trying to get the problem solved.

robobass · #6 02-16-2011, 06:29 AM

Quote:

Originally Posted by Heifetzbass

On my own extension, I just add a small piece of leather to the existing leather when it gets worn and doesn't stop the way I like. (It gets compressed after a year or so.) I buy the leather at a hobby store and attach it to the previous leather with superglue.

BG

Warning! Bonds skin instantly!
I have heard that superglue was actually invented for use in surgery. What is leather but skin? Superglue bonds exceptionally well to leather, but watch out for those vapors!

Cody Sisk · #7 02-16-2011, 06:34 AM

On my KC extension I put a wide groove in the capo for the string then I glue on a thick piece of belt leather (5-6mm thick). I then close the capo on the string and over tighten it. After letting it sit for 10 minutes or so under this pressure, I'll then adjust it to the proper tension for use. The leather seems to hold its compression. I haven't had a problem yet with buzzing. If you need some leather, I can spare a few scraps, come on by..

CPike · #8 02-16-2011, 08:55 AM

Thanks, as always, to all notions offered here!

@Cody - I approach my own KC ext in a similar manner; I've re-padded it once in the 5 years I've had it on. The difference is the footprint of the contact point of the Robertson capo is tiny by comparison. Also, because the Robertson capo isn't height-adjustable, there isn't enough room for a thick piece of leather.

@Rob - I will try the hide glue trick you suggested, plus I'll examine the capo angles when I see the bass again. I'm sure Robertson's would be happy to resolve this, but my friend has an audition coming up soon and probably cannot afford the time to get the bass out there. I'll try to contact them directly to see if they have any ideas I can try.

.cdp

CPike · #9 02-16-2011, 09:09 AM

There's a maintenance manual on Robertson's website:
robertsonviolins.com/uploads/C-Extention%20Booklet-2.pdf
It suggests applying some powdered rosin to the contact point to prevent slippage...

.cdp

CPike · #10 02-17-2011, 01:45 PM

Immediate results with the powdered rosin trick! All is well...

.cdp

mjt0229 · #11 02-17-2011, 01:58 PM

Quote:

Originally Posted by robobass

Warning! Bonds skin instantly!
I have heard that superglue was actually invented for use in surgery. What is leather but skin? Superglue bonds exceptionally well to leather, but watch out for those vapors!

I've heard that story too, but I was also told that the formula that's commercially available isn't safe for use on human skin - so don't get any ideas about patching yourself up with it.

forester · #12 02-17-2011, 04:15 PM

Quote:

Originally Posted by mjt0229

I've heard that story too, but I was also told that the formula that's commercially available isn't safe for use on human skin - so don't get any ideas about patching yourself up with it.

that all might be true, but i have used S-glue and accelerator many times to knit what would otherwise be crippling cuts lingering on my hands for several days. there is a learned art to the application though.

robobass · #13 02-18-2011, 06:37 AM

I'll use it on a cut once in awhile. I don't know if that's good or bad. But, if you use it on your latches be very careful that no glue gets on the contact surface. It makes the leather very hard and would likely damage the windings. Also, I don't really dig the rosin idea either for the same reason. If the latches need extra friction against the string, or high rotational resistance to stay closed, then the problem is most likely with the geometry. Is is possible that the scroll got bumped in a doorway or something?

CPike · #14 02-19-2011, 11:47 AM

I saw no evidence of geometric issues; all capos were angled the same and the contact points were parallel with the fingerboard surface. The only perceivable difference between the capos that held and the ones that didn't was the softness of the leather. (For the record, extension adjustment issues are not unfamiliar to me - this is just the first time I've dealt with a Robertson's extension.)

I didn't think superglue was a good idea - too messy! I was prepared to use the diluted hide glue idea, had the powdered rosin not worked, but the rosin results were instantaneous. My friend is very happy with the outcome, and I'll keep an eye on her string windings to make sure there's no damage.

.cdp

Heifetzbass · #15 02-20-2011, 07:34 AM

Seriously guys, superglue is not that hard to deal with. I don't use it to glue seams, but attaching a piece of leather to another piece of leather via CA is not hard, nor dangerous if you just use a drop or two.

Obviously, don't use the whole tube or use it while the capo is attached to the extension. Wear protective gloves, respirator, safety glasses, etc... use a plastic glue "pusher" hold it in place for 20 seconds, and done.

I am not advocating the use of CA for any other kind of repair.

BG