It is a remarkably small, light and smart little mechanism. It works by using two pulleys of different diameters which are machined from one solid piece of metal. So no slippage is possible between the pulleys . Around these two grooved diameters is wrapped the gear change cable. A flat is machined on one side of the pulleys to allow the cable to "cross over" between the two different diameters. The cable being wrapped twice around the pulleys. The pulleys run on a miniature, rubber sealed, journal bearing hidden and protected within the ShiftMate mechanism's body.
The difference in the two pulley diameters effectively changes the pull per click ratio of the gear change lever. It can thus be used to match a lever to another "alternative" gear changer and cassette. By this clever method (and the correct choice of pulley wheels) almost any gear lever, cassette and changer combination can be made to work.
The twin pulleys can be easily reversed by removing the centre screw to increase or reduce the pull per click. A whole range of pulleys are manufactured to cater for different combinations of gear lever, cassette and changer. The supplied chart lists 4 pulley sets offering no less than 29 lever/ changer/ cassette options! These are almost entirely different combinations of Campagnolo and Shimano products. Only Sram is largely ignored.
The most obvious use of the ShiftMate is when indexed gears would hop over, or fall short of the required lateral chain movement, when changing gear. The more gears involved the smaller the possible error before gear changing becomes a nightmare. In my own case it was the 4th largest sprocket which could not be reliably selected using a 10sp Ultegra rear changer and a 10sp cassette controlled by Campagnolo Ergo 11 speed levers.
With the trike up on the work stand and the ShiftMate in place I was able to click solidly from gear to gear without hesitation. The previous problem with the 4th sprocket seemed to have vanished.
One slight oddity is that the ShiftMate mechanism has a flat machined on the low end of the body where the gear cable exits. This flat rests against a supplied nipple which is inserted into the rear gear changer, cable adjuster. The flat on the bottom of the body makes the rest angle rather critical. This angle is controlled by the angle of the rear changer itself of course. But also by the short length of cable housing (outer) between the ShiftMate mechanism and the usual chainstay cable stop.
Since the mechanism "bends" the cable approach to the rear changer by quite a large angle there is no longer a need for the usual high cable curve to ensure low friction. The shallow curve of the cable can be seen in the attached image. (More images to follow in better light)
If the machined flat does not lie tightly against the nipple then there is space for cable slack which alters with cable tension. It might have been better if the bottom of the housing had also been bored like the top. Then a longer nipple could physically join the body to the rear changer's cable adjuster to remove the potential cable slack from any rest angle error.
Even when the cable was tensioned as hard as I could pull with my hand there was still slack on the bare length running beside the trike's down tube. I took out the slack with the cable adjusters but it still needs work to avoid a dead click when changing from top gear. I may need to shorten the curved outer slightly more.
I don't think there is any risk of damage to the rear changer or the ShiftMate from a more rigid fixing between the two. There should be enough flexibility in the final length of outer cable. The rear changer can also rotate about its pivot screw. I'll see how things look when I shorten the cable outer slightly more tomorrow. The image alongside shows how close the pulleys are to the trike's reinforcing loop. This would never occur on a bike.
I think you will agree from these initial images (taken in half light under a heavily overcast sky) that the device is very compact and really quite attractive in appearance. While the success of its gear changing ability is the the main criterion the unit cannot be said to mar the appearance of any cycle. It is certainly a fine match for my (rather filthy) R931 stainless steel trike. Though one wonders how long the device will keep up its pretty appearance without detailed cleaning. We shall have to see how it copes with salt spray from winter roads, . I can see the rust coming through even on the chromed axles of the Shimano SPD pedals.
The only real disappointment with the device is the cosmetic "ding" on the edge of the machined body. The ShiftMate is priced at £38 plus P&P by SJS. At this price level (and over a month's delay) I would really have expected cosmetic perfection. Fortunately the damage is quite difficult to see in normal use on a trike because of the rear wheels. It would be very obvious if it was fitted to a bike. The damage must have been perfectly visible before packing in bubble wrap and air bags within the cardboard box. It certainly didn't happen in transit. Perhaps they didn't believe that I hadn't received the first one? So were unwilling to trust me with a blemish free "second"?
The first ShiftMate never arrived and their quoted track and trace number never registered on the Royal Mail website. When this was pointed out to them at SJS Cycles they asked that I wait (for nearly a month!) before contacting them again regarding non-delivery. I consider this totally unacceptable behaviour from any online dealer. Non-registration of a tracking number from day one should have sounded instant alarm bells that something was very wrong. Either with their own despatch system or their delivery agent's!
This one arrived via UK ParcelForce and GLS five days after despatch including the weekend. Three to four working days is normal for packet delivery from the UK to Denmark. Tracking on the Royal Mail website consisted of an unchanging "In progress". Only when I checked the GLS website did I get the full tracking details. The reason the original didn't turn up? See below:
I'll just have to put the trike back on the stand and have another fiddle. There must be some difference between letting cable go slack and reeling it back in again. This suggests backlash in the system is spoiling the symmetry of the cable length when going up and down the gears.
After the final length of outer was clipped a little shorter the change seemed a bit more crisp. I played with the cables adjusters a little and left them in the best position. It occurred to me while I was changing up and down the gears that the adjusters don't alter the cable tension. They change the cable's nominal position or length. The tension remains the same throughout the range of cable movement since it applied by the spring on the changer. Indexing results from the cable being let out and rewound in accurate steps. The changer doesn't care how the steps are applied and is incapable of stepping itself. The cable length slightly alters the lateral position of the changer at any one point in its travel depending on the gear selected.
The present position is that the chain is probably quite worn. Which is affecting the gear change. I just tried the chain measuring tool and a new chain should really be fitted soon.