Upgrade for users of 1/2" mylar belt


This thread will be of interest to Galibier, Redpoint and Teres belt drive TT owners, or anyone using or thinking of using a drive belt made from 1/2" mylar. The belt material of choice on these tables for several years has been the silver holographic mylar streamers from sources linked on the Teres and Galibier websites. This outperforms everything else we've tried but like anything it's not perfect - and we've now found something better.

One of the silver holographic mylar's assets can also become a liability. That metallic layer, when new, gives the belt exceptional "grip" on the platter and motor capstan. Minimal slippage on transients is one reason the material works so well. Unfortunately, that layer can wear over time, leaving a silvery gray residue and allowing performance to deteriorate. The only solution has been a good cleaning and a new belt. No big deal, but if there was a better or more stable belt Paul and I wanted to find it.

I'll spare you a recounting of our many experiments and jump to the good news: thanks to (yet another) brainstorm by my resident genius/partner, we've developed a belt that both performs better and lasts longer. I've held off posting until we were sure, but after 4 months of steady use Paul’s idea is still working perfectly. The only negative is that making this new belt takes an hour or more of work spread over two days, but to us it's worth the effort.

HOW TO MAKE ONE

1. Cut a length of the silver holographic mylar tape sufficient for your TT, plus 3-4" extra.

2. Remove the silver metallic coating off the backside of the mylar. Paul used an acid etching cream popular with stained glass hobbyists to dissolve the metal - safe, quick and easy (use skin and eye protection).

3. Rinse thoroughly under running water, inspect to make sure you got all the silver off, wipe and hang to dry overnight.

4. Splice as normal to make a TT belt, making sure you tape on the OUTSIDE (which will be smoother than the now bare inside).

5. As always, the best splicing technique is to overlap the ends and cut on a 30-40 degree angle. Apply 1” video splicing tape (*not* tabs) across the belt at the *same* angle and trim away the excess.


WHY IT PERFORMS BETTER

Unlike any plain mylar ribbon you could easily buy, the silver holographic streamer has an ultra fine texture embossed on the back side of the *mylar* during manufacturing (*before* the metallic backing is applied). Once the silver layer is applied you can't see this texture, but that's what diffracts light like a million tiny prisms to produce the shimmery rainbow effect. Stripping the metal backing away exposes this texture, which becomes the contact surface of your new belt.

Paul realized this texture must exist and then hypothesized that using it for the working side of a TT belt might provide more “grip” on the platter rim and motor capstan than either plain mylar (which is extremely smooth) or the metallic backing. He was right. This belt produces more lifelike dynamics, both macro- and micro-, than even a brand new silver holographic belt - which heretofore was the best.

WHY IT LASTS LONGER

Removing the metallic backing exposes bare mylar, which is much sturdier than that fine layer of metal. Under normal use and assuming no accidents, one of these belts should last many, many months, perhaps years, while delivering consistent performance. Ours is going into its fifth month with few visible and no audible signs of wear.

Different motor capstan materials might interact with this belt differently, but I urge anyone with a compatible table to give this a try. Like all our favorite little tweaks, we'd find it hard to go back.

A FEW TIPS

1. Clean any silver/grey residue from your old belt off the motor capstan and platter before mounting the new belt.

2. As many of us have learned, the more inelastic the belt, the more critical motor leveling becomes. That is truer than ever with this new belt. Getting the motor set just right is touchy. Take care that your new belt is riding level in the center of the capstan before you start to play. You don't want it sliding up or down and mangling itself.

3. Motor distancing is also more critical than ever. Since this belt will not slip *or* stretch, tension must be perfect. The right amount is just shy of the tension that would tilt the motor off its feet.

4. Depending on your climate, the belt can build up static potential during use. Not enough to spark, but more than enough to attract airborne dust. I dust the belt's inside with my CF brush after each side before stopping the platter.

5. With this or any belt, always start your platter spinning with a helping push. Just pressing the motor's ON button creates lots of belt-wearing friction as the rapidly spinning motor tries to drag that heavy platter up to speed.

It all sounds like a pain, and it is! But the sonic and longevity results are worth the effort.

Cheers,
Doug
dougdeacon
Do you guys have a recomendation for a VPI Scoutmaster TT, I would like to try something other than the belt that comes with the TT.
I've read some good reports about various kinds of thread, string, fishing line, dental floss, etc. I also remember one VPI owner who modified his table to accommodate a wider belt, used 1/4" wide mylar and reported good results.

The difficulty in implementing this kind of belt on a VPI (correct me if I'm wrong) is that the motor capstan and/or platter rim are grooved for a fairly narrow belt. This limits your material choices to whatever will fit, unless you modify your table.

If your platter rim is flat, getting a local machine shop to make you a taller motor capstan might be viable. For a 1/2" belt you need a capstan working surface height of about 9/16" to 19/32", very slightly convex and with lips at top and bottom to stop the belt riding off. The O.D.at the center would be the same as your existing capstan, obviously. Material choice probably isn't super-critical, but the surface should not be highly polished.

The key characteristics in a good belt material are:

1. Lack of elasticity. The more resistant the material is to stretching and rebound the better. Rubber is terrible (sorry). Mylar is dimensionally very stable. At the speeds and loads experienced by a TT belt it wouldn't be far wrong to call it "perfectly" stable, depending on the thickness.

2. Lack of "slipperiness", ie, sufficient friction to prevent slippage when a big transient tries to slow the platter. This is tricky to get right. The biggest risk of slippage is at the very short belt/capstan interface. The belt/platter interface is long enough to make slippage less likely there. The optimum material is very much table dependent. On a Teres motor capstan materials like string, thread, etc. result in quite audible slippage, though they're still better than anything elastic. Mylar will also slip if it's too thick and/or too smooth to make the curve around the capstan, and that's a function of your capstan diameter, material and surface.

Not much of an answer, sorry. But I encourage you to experiment. It can't hurt and you'll certainly learn something from everything you try, as we have.
what sort of concentration etching gel do you use? google searches return various types of acid precentages, 10%-38% acid content. i will be trying this on a tw raven one. i will need 1/4".
seems like all the sources are for 1" or 1/2". does anyone know where one can find 1/4"