OTARI MX-5050 1/4" and 1/2" Pinch Roller
OTARI MX-5050 Pinch Roller
This Pinch roller is new fresh manufactured in the EU for Nagravox using a modern synthetic black rubber formulation.
The 1/4" has the standard sintered bronze bush moving assembly and the 1/2" uses our 'deluxe' moving assembly with special low noise precision roller bearings instead of plain bushes.
All our kits and parts use specially sourced, new, freshly manufactured components from reliable manufacturers whom we have been dealing with for many years. NO NOS (new old stock) NO 2nd hand items!! Never buy or use a 2nd hand pinch roller - its just not worth it!
Nagravox continually researches pinch rollers, manufacturers and materials and is pleased to be able to offer a comprehensive assortment for a number of machines. Although we are specialists in Revox, Studer and Nagra we are also responding to many inquiries for other makes.
SHARING SOME EXPERIENCE and RESEARCH on PINCH ROLLERS
WHAT DRIVES WHAT. Myth busted. The pinch roller does not drive (or more correctly regulate) the tape motion. The capstan shaft does! The pinch roller only provides the force necessary so that the tape and capstan shaft are kept in intimate non slip contact with each other.
HARDNESS / SOFTNESS. Because the pinch roller minimises slip between the tape and capstan shaft, it must be hard enough not to deform too much which would compromise an even pressure over the full contact area. Further, one does not want the edges of the pinch roller (outside the width of the tape) to deform around the tape and contact the capstan shaft too strongly thus reducing the actual ability of the capstan to drive the tape. In short, a soft pinch roller is not good, will probably increase wow and flutter and also not last long.
PR PROFILE. Researching the history of pinch rollers, Studer, a leader in its day, tried many different formulations, bush systems and profiles. Originally profiles were wide, flat and pinch rollers harder. Then they tried reducing the edge conflict by reducing width and profiling with a slight convex shape and softer ADP formulations so pressure was concentrated in the centre. The problem with this is that it is difficult to align the tape exactly at the peak of the convex profile. Then they went back to a flat profile and a harder formulation. No doubt if Studer had continued we would have seen other trials and tribulations.
AGE. How old is that 'new' pinch roller you bought? There are a mere handful of pinch roller manufacturers in the world . Some cling to old dated designs and profiles. Others believe they will make a fortune by making them as cheap as possible. Some vendors even offer to 're-rubber' your old ones - eek - what about the wear in the soft brass PR bush? Cheap Chinese I believe are available at bargain prices now with vendors and proxies in USA and EU. A significant problem is many vendors acquire over the years NOS stock of pinch rollers at a bargain price. Ask them manufacture date - anything more than 3 years - its already past its 1/2 year life. You get what you pay for.
The condition of your motor shaft is paramount. A shiny shaft matching the tape profile is an indication the shaft has done a lot of hours work and will not grip the tape effectively resulting in an increase wow. The shaft should be a dull grey colour. Shafts can be reconditioned and the dull grey restored using a special micro bead blasting technique.
The tape tension is also important because the PR / capstan is a regulating system not a driving system. This is controlled rudimentarily in early and most tape machines with back tension fixed but in more sophisticated machines it is measured and controlled dynamically and can be precisely set / calibrated.
Both formulations used in our pinch rollers are carefully determined and controlled so as to maintain surface contact rigidity and minimise wow and flutter over their lifetime. Sometimes we offer ADP and others only black rubber and some both - this is based on our findings as best for the model considered.
Pinch rollers with rollers bearings. Some manufacturers' made their pinch rollers with single or dual low noise precision roller bearings. This was primarily to reduce pinch roller shaft wear in the long term and also to better position the tape and pinch roller profile so the tape was in the middle of the pinch roller. The geometry was thus easier to control during manufacture and results in a more precise pinch roller bearing motion system. Claims have been made they give better wow and flutter performance. I have not found them to be better or worse frankly. I like them from an engineering stand point but cant really say they are vastly better in terms of performance. On high speed machines 30"/sec they do tend to be a little noisy compared to the sintered bronze bush. Because they are sealed and lubricated for life, their life in hours may be less than a sintered bronze bush. However, these days most pinch rollers rubber deteriorates with age and this is the life limiting factor really.
What's the realistic life of a pinch roller? Whichever comes 1st. 1000 hours (mechanical wear) or 5 years (rubber deterioration).