13 Sep 2010

Trike brakes.

*
 Most trikes use two normal "bicycle" brakes at the front. Only a very few riders use any kind of rear brakes. Though hub brakes have always been available and were used on some trikes at the rear. Rear disk brakes are a relatively new phenomenon but have become the norm for massed start races for "disabled" trikes under UCI rules.

Only occasionally were side pull brakes fitted at the rear on crossbars fitted across the seat stays. I experimented with this idea myself but quickly gave up due to the rear wheels locking the moment I applied the brakes in the wet. I had steel HP rims at the time so that may have affected the matter. Others seem to like the idea. Dave Overton used a similar set-up on his trike at Warwick. Where he came second.


Dave Overton's trike at Warwick with (and using)  twin rear, side-pulls. 
Image from British Cyling's Flickr webpage. (Cropped and resized)

It occurs to me that a pair of side pull brakes could be incorporated into the compulsory, rear "safety bumper" to pander to the lunatic UCI rules for handicap massed start racing and (now) TT trikes as well. Such an arrangement would be much cheaper than a pair of disk brakes and very much lighter in overall weight. The bumper must be fitted anyway. So why not incorporate the brakes? Disk brakes require very expensive mods to standard trikes.  They may also drag or have "difficult" braking behaviour.

An added "crossbar cum safety bumper"  is just extra dead weight. Much like the brain dead idiots on the UCI rules committee in relation to cycling. They have made themselves indispensable to the designer jewellery branch of bicycle design. So we might as well play them at their own game of constantly moving the goalposts. 

They say that two independent brakes on the rear wheels are a requirement. No mention of standard stirrup brakes being excluded. Every road racing bike on the planet has cable-operated, stirrup brakes. They are well proven over a century of use in all types of cycling. All they require is a twin cable handlebar lever to be operated in perfect balance. Side pull brakes operate smoothly without any nasty vices. The total cost of adding these brakes to a standard trike can be as modest as the depth of pocket of the rider or their sponsor. There is a huge selection of brakes to choose from. No doubt Geoff Booker of Trykit could easily adapt his UCI rear bumper to take a pair of side-pulls at very little extra cost. 

The White Winter in Denmark, last year and this, went on for literally month after month. The roads were continuously iced over, covered in snow or just very wet on every ride. I rode with twin front brakes on the Higgins with skinny 700 x 23mm Bontrager tyres all round. I rode over sheet, black ice, going downhill many, many times and never felt the need for rear brakes. The trike stopped quickly and safely under all circumstances with the front brakes alone. 

Had I fitted rear brakes might have been tempted to use them. Had I so much as touched those back brakes under the difficult conditions I faced, every single day, for all of those months, I would probably not be here to write this blog. The rear wheels would have locked instantly due to their perfectly normal, light loading. With consequent low traction and adhesion. The trike would have quickly broadsided out of control. At right angles to the direction of travel the leading back tyre would have caught in any roughness on the road, snow or ice. The trike would have cartwheeled sideways in a flash. With me firmly attached to the pedals spinning arse over tit along with the trike. 

Various parts of my head, body and limbs would contact the ground and surrounding scenery in rapidly repeated succession. Most of my routes have trees lining the road at very close quarters. What would have been my chances of survival on the empty lanes I usually frequent to avoid the traffic on the main roads? I could have lain there critically injured for an hour or more before a solitary "rat runner" or farmer had used the lane. With only two front brakes I remained perfectly safe, on any surface, for a couple of thousand miles of this difficult winter riding. 

Do the brain dead UCI committee of dictatorial rule makers actually ride trikes? Have they ever ridden a trike even once in their lives? Or do they just sit in smoke-filled rooms? Desperately plotting new rules to make cycling much less fun and a bløødy sight more dangerous? (pun intended!)

I'd be prepared to lend them my Higgins to try on a slippery test track just to see how they get on with front brakes alone. Then they can borrow a trike fitted with rear disk brakes and see how they get on with those. On second thoughts perhaps this wouldn't be such a good idea. The lunatics would have all bike and trike riders wearing body armour, knee and elbow pads and full motorcycle helmets with visors before the day was out! With compulsory fire extinguishers, air bags and several flashing beacons on every trike! Just in case...

Note: It seems that others do not have my allergy to rear brakes. Both disks, drums and side-pulls have all been used on trike rear wheels and the owners seem happy to have them. 
______________________________________

Below are a series of images of paired front brakes on standard trikes.  The unusual arrangements are  necessary to avoid conflicts between brake blocks where two brakes are mounted in front of the forks.


My own Higgins with centre-pull brake on hex extension bar in front of cantilevers on brazed-on fork bosses. This was back when I rode on sprints and tubs.


A similar arrangement on Steve's lugless Higgins.
The typical hexagonal brake extension bar is brazed to the fork crown.



Side pull brake on a very long, chromed extension in front of cantilevers on a Longstaff. 
(image found online, source unknown)


A Jack Taylor found in an online image search some time ago.


Interesting, Resilion, clamp-on callipers with a side-pull fitted on a short extension in front. I recognise the cantilevers but can't think where from. It must have been a very long time ago. (eBay auction image) My brother remembers these brakes being popular on tandems and recalled the name a little later. The long brake blocks probably offer superior stopping power.


Side-pull and cantilevers on Alan's beautiful Longstaff.


Twin centre-pulls in a poor image scavenged from eBay.


Centre-pull in front of cantilevers on Jack Taylor on eBay.



My Longstaff conversion with an inverted-cable, twin-pivot, side-pull to the rear of the forks to avoid cable contact with the down tube. A loop of cable/casing ran down beside the fork leg and back up again in a deep U-form. Not a good idea at all. The casing filled with rain and muck and caused friction. The "feel" of the brake was very poor even when first set up and well lubricated. It went rapidly downhill from there.I could easily envisage two cable stops, an a bare section of cable around a pulley (just below) to change cable direction. This would require brazing, of course, but might offer an alternative way of safely applying a cable to the bottom of a suitable, side-pull brake.

Note the ring of damage to the down tube on this recycled frame. The same occurs on the top tube. The bike probably suffered a severe, head-on collision at some time in its life. Which stressed both tubes beyond their elastic limit.  It has now been taken out of action for safety reasons. The entire bike (but not with the trike conversion) only cost me £5. equiv. so it doesn't owe me anything.

Campag side-pull with cantilevers on an immaculate Longstaff.
(Image found online)



Dreirad's superb 1954 Higgins trike restored to as-new condition with a smart LF hub brake and a side-pull on the forks. A neat, all-weather combination. His trike looks as if it has just left the showroom!  I particularly like the crimson paint. Wonderfully evocative of quality cars prior to the cheap, mass-produced models of the 1960s when car paint "went bad".

If anybody else would like to share images of their upright trikes on the blog please do get in touch.
-----------------------------------------------------------

Few brakes lend themselves to a position behind the forks because of their vertical cable entry (or cable pull) of their design.  The cable (or usually parts of the adjustment mechanism) will strike the down tube whenever the handlebars are turned in a particular direction. This leads to cosmetic damage and may even dent the down tube over time. It may strain the metal of the brake itself leading to sudden and catastrophic breakage. It also adds a severe and unwanted limit on turning ability in one direction.

There are now some interesting new brakes coming onto the market. Probably aimed at the low drag demands of the time trialist and the nostalgia wave of the "fixie" enthusiast. With the latter the clean and simple lines of a classical track bike must be made safe and roadworthy. Usually by adding a front brake to go with the compulsory fixed wheel. A freewheel would require two brakes. A rear brake on its own is both dangerous and illegal in many places. Though Denmark has long allowed a single back pedal brake on roadsters. I'm not sure this is still allowed. I shall have to find out.

Good braking is essential to real speed on the road. You must be able to accelerate and ride at any speed of which you are legally capable. Then be able to scrub off the speed safely and rapidly with the brake(s) to take corners while well under control or to slow for obstacles. Poor brakes mean you must hold your speed down all the time in case of corners or potential accidents. This is an incredibly slow way to get about in or on any vehicle. Let alone a pedal driven bike or trike which already has severe limits on it maximum speed because of the human engine and severe wind resistance.

Fixed wheel alone on the road is delayed suicide. Not only does the braking only work on the back wheel but it has not the force to slow you quickly like a proper front brake. Particularly on a trike! On the race track everybody is going the same way. This is certainly not true of the road! Fit really good brakes before worrying about drag or appearance. It will make you much faster. Just ask any racing motorcyclist! Good brakes are worth much more than a few extra horsepower.

A neat brake behind the forks will help to maintain the illusion of a true "no brakes" track bike. These new brake designs pull and push the stirrups simultaneously, but do so directly from the side. So that the cables do not interfere with the frame down tube even when the handlebars are fully turned either way. Handy for when you are doing track stands at the lights! (On a bike) A trike merely becomes a comfy armchair at traffic lights.

What is shocking is that none of the big players has ever produced a brake which could safely hide behind the forks of a normal bike. In fact most manufacturers seemed to go out of their way to make brakes even more difficult to fit there. With foolishly long stirrup extensions and strongly asymmetric designs. Which seemed to have far more to do with appearance than function.

Tektro should be highly commended for their daring in br(e)aking away from the well trodden path of the long established manufacturers. It is rumoured that even more daring designs are due soon. To hide the mechanism right inside specially designed carbon fibre forks on high-end TT bikes.    


The Taiwanese Tektro [R725] and Oval [A700] are examples of the new design. Though they may both be made by the same Taiwanese factory. This illustration shows both names marked on the same brake! Case proved?

The geometry of these new brakes does not look as if it has been fully optimised yet. [IMO] They have taken a basic centre pull brake design. Then adapted the ends of stirrup levers so the cable action is from one side instead of pulling equally from (centrally) above.  There has been no obvious attempt to improve the geometry of the leverage to match this design change. The mechanical advantage is much reduced in comparison with the original centre-pull design. See my drawing above:

In the new design the pivots should ideally be lowered to achieve the same sort of leverage as a centre-pull. Note the considerable reduction in leverage between X and Y:  X:Z  > Y:Z. Only the leverage on one stirrup is shown for clarity but makes no difference to the argument. Since the brake is bolt mounted to the forks conventionally it does not use braze-on bosses. So the stirrup pivots can be moved at will by the designer. By lowering the pivots the ratios of the moment arms would be restored. Perhaps it is unimportant for a brake intended for time trialling on dual carriageways? Though a reserve of powerful braking is always desirable for emergencies. Like all of those moments when a cyclist becomes completely invisible to drivers despite the head to toe, day-glo clothing.

I have read some criticisms of the braking power of these new Tektro brake designs online. Hopefully the braking power is still adequate with the present proportions between force and action. It would be a great shame if this useful design failed through poor adaptation to the side-entry cable arrangement. It has much to commend it if properly designed. Particularly for trikes. Saving us the complication of having to have twin front brakes in front of the forks. This may look quite "techy" but it is still a rather clumsy arrangement.

It is absolutely certain that riders of Time Trial bikes and road going "fixies" will buy vastly more of these "stealth" brakes than those needed to convert the world's entire fleet of upright trikes. Even if you could persuade every trike rider on the planet to do so.


A pair of Tektro R725s, in front of and behind the forks, are shown on the Trykit website.




Here's an image of a neat, Trykit, double, Mini-V-brake set-up. I would imagine this is a very powerful braking system. Again, the cable side entry completely avoids the usual conflicts between cable and downtube. Though at the expense of two more brazed-on bosses. No problem on a hand-built Trykit. Slightly more difficult to copy with bog-standard bicycle forks. I wonder whether Geoff Booker at Trykit would sell a pair of ready-made forks like this?  Thanks to Martin.B for the image.


Click on any image for an enlargement. Back click to return to the text.

2 comments:

  1. My Higgins, an ebay basket case, was refurbished last year. The frame was the only original part, the brakes were two weinmanns bolted together. I replaced these with a new hub brake as the front wheel needed replacing & a new double pivot brake. Forks were drilled out to take the new Allen bolt fitting, a long Allen nut extender holds the mudguard.

    ReplyDelete
  2. Hi Dreirad, That's an interesting approach to the braking problem. Do you have any pictures of your trike I could share on my blog? Upright trikes are so rare it's always nice to see different machines and the way the owner has built them up. You can email image attachments to triker (at) nypost.dk if you have any. Thanks.

    ReplyDelete