16 Mar 2010

More Trike Fettling

*Here's the donor rear wheel hub after the Shimano freehub sprocket carrier had been removed. Note the "star" shape which drives the hub. The internal thread is for the tubular axle extender which supports the freehub and outboard bearing.

The Higgins chapter was getting a bit long so I'll start again from the point where I was struggling with the gears. The newly fitted ARX rear changer had a longer roller cage than the Dura-ace but still struggled with the wide ratios I was using. 46-26 is 20 teeth difference on the chainwheels. 13-23 teeth on the rear sprocket block is another 10 teeth for a total of 30 teeth.

After some hours playing with the gears with the trike upside down, right way up and on the road I finally decided to use and modify the TRYKIT hanger. My problem was that the rear changer did not fold itself close enough to the sprocket block. The body of the changer was hanging in an almost vertical position on most gears. The original hanger brought the gear changer under the block but placed it much too far away for a clean change. The TRYKIT hanger moved the changer to the rear but still not close enough to aid changing. So I used a brand new abrasive wheel on the bench grinder to work gently at the surface where the rear changer stop screw presses on the TRYKIT hanger. A trial proved that a file didn't touch the hardened material. Even with the screw completely removed the changer hadn't come close enough to the block. With only a couple of millimetres ground away the changer folded down perfectly and the screw could now be used to fine adjust the clearance from the sprockets. I also lengthened the chain by one full link to ensure the cage was vertical when on the third from largest sprocket and on the 46T chainwheel. This allowed the chain to go (usually accidentally) into bottom gear on the largest chainwheeel without causing any damage. The overall result was an immediate and marked improvement in gear changing.

The new dropped handlebars had a remarkable effect on the feel and handling of the trike. It suddenly seemed incredibly light and responsive after the tri-bars were removed. I had feared my back would dislike leaning lower over the bars but the converse is true. It feels far more comfortable than sitting upright with my hands resting on the tri-bar pads. Riding on the brake hoods is also very comfortable and where I spend most of my time on the flat and downhill. The Shimano, bar-end, gear levers fall very naturally to hand. Requiring much less hand movement and fumbling about than down tube shifters. This all became second nature within a few miles. I ride on the centre of the bars only to climb steeper hills now. My daily speed and distance is rising steadily considering how hilly it is in my area.

Today, I was feeling very strong and set a new personal record for the hour of over 40 miles! :-) The battery was nearly flat in the new cycle computer as witnessed by the almost illegible grey text on the screen. For some reason the mileage was rising by 1/10 of a mile much faster than 1/100th on the previous computer. It was like a scene from The Time Machine but with the miles whizzing past. I had set the wheel circumference correctly to 2117 (for tubs) and the speed readings seemed reasonable enough. It was just the distance indication which had gone completely haywire! A new battery has solved this problem. Though I wish they'd put a raised rim around the little screen to stop sunlight from casting light and shadow into the screen area.

The saddle is proving a keeper but I still have to keep shifting backwards. Perhaps I need a shorter handlebar extension? Or should try moving the saddle forwards? Sheldon Brown has much to say on the subject and much of it useful and sensible advice:

Bicycle Saddles

I punctured one of the old, rear tubs in less than 100 miles and rather panicked at the thought of replacing tubs regularly following attacks of flints and thorns. Discussion with a number of bicycle shop staff suggested that few Danes use tubs even for racing. None carried much stock and several said they rarely sold more than one tub a year! Clinchers, wire-ons or High Pressures in my own, geriatric terminology, were the thing to use these days. Or so it seemed.

However, finding unicorns would be easier than finding HP trike wheels in Denmark! I dragged out every spare wheel I had in the shed and considered what it would take to use the rims to build new HP rear wheels for the Higgins. Wheel building was not something I had ever tried before. Though I'd replaced broken spokes and trued my own wheels since I was a teenager. None of my wheels had 28 holes to match the Rogers/Higgins trike hubs though.

So it looked as if a set of new TRYKIT hubs at £70 a pair and a few hours learning how to lace spokes and tension them into ridable wheels loomed ahead. But I bought a Schwalbe Montello training tub for about £20 anyway and prayed to the evil puncture spirits to leave me alone.

Prior to making a decision about wheels I weighed the present trike wheels with 28 DB spokes and Mavic sprint rims at just under 3 lbs each with a tubular tyre fitted. The Longstaff rear wheels with Bontrager Racelite 700 x 23 HPs weigh just over 3.5 lbs. My lightest (700C x 23 x 32 stainless plain gauge spokes) aero bike wheels with 700 x 25mm HP tyres (and axles removed) also weigh a tad over 3.5 lbs. The normal 36 spoke HP front wheels of all kinds, including both aero and narrow road type, all weighed around 3.75-4 lbs each with narrow tyres fitted. I used a spring balance fishing scale hanging by a chord from the shed roof timbers to weigh the wheels.

So there isn't very much in it but the tubs and sprints win on lightness, low rolling resistance and a bumpy, but lively, ride. They certainly aren't uncomfortable and I ride the 200 yards of the gravel drive with much less discomfort on the trike on rock hard tubs than any HPs on a bike. The tubs also sing and ping as they make smaller stones fly. Somehow I'd forgotten about that over the years since my serious cycling days. It was pleasant to be reminded again.

Later I looked online and discovered that some Mavic clincher rims are actually quite affordable. All my recycled bike wheels are showing cosmetic distress and ugly brake block damage. Lightweight, semi-aero, track rims are much prettier and probably worth the expense compared with dismantling old wheels which have already seen quite a few miles. The Alesa rims on the Longstaff look absolutely superb to my eyes. With a perfect combination of lightness and a small aero section for a subtle, but up-to-date appearance. They also have no ugly and totally unnecessary braking surfaces. Coming from an older generation, used to really skinny wheels, I'm not a great fan of the very deep aero rims. They just look so heavy and ugly to me. On the other hand, a set of 3 spoke carbon wheels are unlikely ever to appear in my stars, so there's no point in wishing they would. Though they seem to be increasingly popular with the serious, trike time trial and racing fraternity.



Geoff Booker of TRYKIT is making special adaptors to allow these wheels to be fitted onto trike axles.

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