A sidecar brake set up for comment

[Andy M]

A friend of mine  owns a sidecar. This beast is 2m wide and could tow a trailer at an all up weight of close to a ton. It therefore seemed (to my friend at least) logical to have brakes on all three wheels. As originally bought off eBay it came with a hideous Watsonian set up from about 1950, a huge bowden cable from the bikes pedal, under the seat to a front master cylinder butchered to hold the cable end. This master cylinder, using 101% of it's travel just managed to get the Ford XR3i calliper to do something. The cable would stick and make the brakes drag, the cable would break at inopportune moments, the whole lot was impossible to bleed due to the imbalance in mastercylinder to slave size and the length of pipe run. Despite this it passed the MOT. 

I My friend therefore decided to look at his options. The bikes rear cylinder is too small to run two callipers. Making a Girling 3/4-inch fit would require new brackets and would probably need a balance valve to stop the Ford side dragging the BMW side into the gutter. Mounting a second small master alongside and yoked to the pedal gives similar issues but at least does away with the valve.

Enter then the idea of keeping the sidecar 100% to itself. A Fazer complete pedal, plate and cylinder was bought and tested. It worked. Balance by varying the forces applied and the ability to tighten and slow in left hand bends. A good solution?

Not according to my MOT tester and some bloke on an MOT help line. The MOT manual says a two wheeled motorcycle made after 1927 must have two brake controls. This means exactly two, not three  I My friend therefore enquired about the possibility of removing the brake entirely. This is fine and correct so long as done neatly and completely and would result in another years access to the Queens highway  What then if someone came along the night after the MOT and fitted a three pedal system? This is unknown. If the system was deemed safe it would be fine, if it wasn't it isn't. Wouldn't adding braking making it safer than no brake at all? Yes, of course it would 

I My friend is therefore seriously considering having a sidecar brake that can be removed in it's entirety for days (such as MOT time  ) when less braking is sufficient. Pictures of the proposed system are here;

https://picasaweb.google.com/104442976739427547289/SidecarBits#

Thoughts, comments or suggestions on where to stick the MOT testers manual will be treated with the appreciation they deserve. 

Andy

[002]

Use a rear master cylinder off a Honda Blackbird or other model with Dual Combined Brakes.
It is large enough to operate twin drum/disc set up on Trikes.
Motorcycle size and shape master cyl..
Plenty around the breakers.

So how does old Brit Bike outfits from '50s/'60s manage at MOT time with two sreperate pedals.
Mind there is a bar across the pedal that will operate sidecar brake when bike brake is applied.
So long as it worked fine I'd pass it....dont see the problem !

Jethro

[johnr]

try and mount the caliper seperate to the hub, on a mount fitter to the wheel spindle but with a bearing so it can rotate, then tie it to the chassis using a tie rod with rose joints on each end. if not, when you hit the sidecar brake, the wheel will unload the suspension till it reaches the top of its travel, in which position it is much more likely to lock up if it hits even a tiny bump. essentially look how floating brake calipers are mounted on wasp or unit front ends, and mount your sidecar brake in a similar way. cos my old oxford had its brake mounted rigidly and the whole thing was pretty much unusable unless the chair was very very heavily loaded.

[Andy M]

try and mount the caliper seperate to the hub, on a mount fitter to the wheel spindle but with a bearing so it can rotate, then tie it to the chassis using a tie rod with rose joints on each end. if not, when you hit the sidecar brake, the wheel will unload the suspension till it reaches the top of its travel, in which position it is much more likely to lock up if it hits even a tiny bump. essentially look how floating brake calipers are mounted on wasp or unit front ends, and mount your sidecar brake in a similar way. cos my old oxford had its brake mounted rigidly and the whole thing was pretty much unusable unless the chair was very very heavily loaded.

I think that must be a specific instance with a leading link? Fifteen years of doing brake type approvals on Landrovers and various trucks and I've never heard of anything running out of suspension travel (We did once have a bus that leaned as the air ran out which wasn't great  ). This one works very well (tested off road of course as the legalility is a grey area  ). The suspension is a trailing arm so the brake loads the suspension. Not that I'd try such things but it locks at about 75% travel when lightly loaded on a reasonably dry road. It would I believe have no problems with efficiency numbers on the ministrys shiney tyre polishing machine.

Load sensing to me is another reason for a separate control (or a valve or ABS). Something like a big old Oxford body could be loaded with 250KG of passengers and luggage and take a share of a 100Kg trailer. A brake set up for control when light is pointless when loaded, a brake for the full load will lock up when light just like John says.

I think it's just mad that they don't know if the control side should pass or fail the MOT. Still, who cares, 11 4/5 months on the ticket and I've still got the wheel spacer!!

Andy

[Steffan]

Where chairs are concerned I know my limitations, but I seem to remember that MZs had braked chairs with two pedals, one for the bike and a combined one which brought the chair brake into play.  Steff

[johnr]

try and mount the caliper seperate to the hub, on a mount fitter to the wheel spindle but with a bearing so it can rotate, then tie it to the chassis using a tie rod with rose joints on each end. if not, when you hit the sidecar brake, the wheel will unload the suspension till it reaches the top of its travel, in which position it is much more likely to lock up if it hits even a tiny bump. essentially look how floating brake calipers are mounted on wasp or unit front ends, and mount your sidecar brake in a similar way. cos my old oxford had its brake mounted rigidly and the whole thing was pretty much unusable unless the chair was very very heavily loaded.

I think that must be a specific instance with a leading link? Fifteen years of doing brake type approvals on Landrovers and various trucks and I've never heard of anything running out of suspension travel (We did once have a bus that leaned as the air ran out which wasn't great  ). This one works very well (tested off road of course as the legalility is a grey area  ). The suspension is a trailing arm so the brake loads the suspension. Not that I'd try such things but it locks at about 75% travel when lightly loaded on a reasonably dry road. It would I believe have no problems with efficiency numbers on the ministrys shiney tyre polishing machine.

Load sensing to me is another reason for a separate control (or a valve or ABS). Something like a big old Oxford body could be loaded with 250KG of passengers and luggage and take a share of a 100Kg trailer. A brake set up for control when light is pointless when loaded, a brake for the full load will lock up when light just like John says.

I think it's just mad that they don't know if the control side should pass or fail the MOT. Still, who cares, 11 4/5 months on the ticket and I've still got the wheel spacer!!

Andy

it is specific to leading link setups, my forks on the beemer did it, ditto the wing and my mates xs, and my sidecar brake did the same, but that was using a watsonian setup, its just physics, if you try and stop the wheel rotating, then that rotational force has to go somewhere. bike suspension is pretty different to land rover stuff.

[hovis]

I used to run sidecar outfits years ago when the kids were young. to get round the mot we used to mount the sidecar brake and pedal onto the sidecar chassis next to the gear lever, I had several outfits like this and never had problems at mot time

[Andy M]

That's good to know. There is a Panther chassis on E-bay with a third pedal too. A bit of further digging has revealed a likely cause of the confusion. The MOT inspection sheet only has boxes for two pedals and their tyre scuffing machine "efficiencies".

Andy

[002]

That's good to know. There is a Panther chassis on E-bay with a third pedal too. A bit of further digging has revealed a likely cause of the confusion. The MOT inspection sheet only has boxes for two pedals and their tyre scuffing machine "efficiencies".

Andy

I'd Pass it ! I gather you have the pedals side by side.
Its all down to the Nominated Tester......IF he understands outfits he would proberbly give it a pass.

I get the Old Brit stuff,Harleys and Outfits to work on and MOT in work.
Because I have the spanners and more of an idea how they work and what to look for.
A lot of it is down to MOT Testers discretion.
Sometimes I get it wrong 
But as I said the old Brit stuff had 2 Pedals....usually the sidecar brake could be used independently
Then when the bike pedal was used a bar would press onto the sidecar pedal to operate that system.

Jethro

[guest146]

I would have thought that if an ABS could be made to work this would take care of  most of the problems. It would invold quiet a lot of work but could be connected to hydraulic brakes on the bike as well. This would need to be removed from a small car or the likes.

Ken

[indiantim]

Interesting thread,

My Guzzi California, has 3 brakes operated by the foot pedal with the sidecar disc, rear disc and 1 of the 2 front disc brakes, and it stops in a straight line with a slight bias to the rear wheel which will lock first.  I am minded to adjust the load sensing valve on the swinging arm to alter this predominance.  There is no suspension reaction noticed  at all.  The big Charnwood Royal even with a trailer attached still feels safe when loaded.

However I noticed on outfits fitted with Hedingham forks, on hard braking a nasty tendency for fork judder.  Due to the design and the use of ball race bearings in the pivot of the front fork.  EZH and Wasp leading link forks have floating disc calipers which overcome this.

Best solution would be a drum brake with an adjustable valve from a early Renault or Mini to achieve balanced braking.  Jethro is correct in using a suitable master cylinder to apply the correct hydraulic forces.  Still like most cars the rear suspension will unload and decrease the force on the sidecar wheel under brake application, hence some decrease in hydraulic pressure by valve control is needed.

As to the MOT, best to take it to a guy who understands outfits, VOSA's finest sidecar expert has retired! so they know FA

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[Andy M]

I would have thought that if an ABS could be made to work this would take care of  most of the problems. It would invold quiet a lot of work but could be connected to hydraulic brakes on the bike as well. This would need to be removed from a small car or the likes.

Ken

This one I can answer. Sorry if this ends up ten pages long though;

ABS solves the brake balance issue so long as there is greater force applied than the sensed wheel can transmit to the road surface. The wheel tries to lock up and the ABS first of all prevents further force getting to the calliper and if that doesn't work releases some of the pressure. It can be crude and unpleasant for the driver (hence most vehicles over 3.5t had a load sensing valve until about 2005 and improved software plus an additional solenoid after that) but it works. ABS cycling only on the sidecar would induce steering input, but what the heck you are allowed 120 degrees on a car steering wheel and it'll pass type approval.

The problem is the sensing. Cars employ 4 sensors and two to four modulator valves. On an axle with two sensors and two modulators it's simple, the wheel slips too much it gets controlled individually. Where the axle only has one valve the electronics look at the rate the wheel decelerated into deep slip and control both wheels accordingly and depending on if they are fronts or rears. The choice is either to modulate both wheels and risk a loss of braking from the wheel that wasn't slipping or not modulate and risk the loss of control from a wheel that actually locks up. Clever systems will switch from one strategy to another once they realise the first attempt failed.

Regardless of how you plumb these 4S/2M, 4S/3M or 4S/4M (Yes Jethro S&M) systems onto an outfit they can get confused by split surfaces (sidecar on ice, bike on wet tarmac) or transitions (start braking on wet tarmac end up on ice). The best case is that confused ABS shuts down and you have a non-ABS system which promtly locks wheels, the worst case is that it prevents braking (best way to do this is to cross the sensor wires so when left slips right gets modulated). You can't take a sensor off as if the ECU doesn't see that wheel start to roll it'll log a fault and shut down part or all of the system. You can fit two sensors to one wheel and put the modulators in series but get a fight started due to the delay in one sensor seeing the effect of the modulation it's initiated and the ECU will have the white flag up faster than you can say "skid". The fault detection with ABS is by comparison as it has to be fully self contained, so it can detect the few degrees difference in sensor positions once modulation starts.

For outfits with ABS the solution is simply to slave the sidecar to another brake. If the wheel tends to lock slave it after the ABS modulator and loose a bit of braking. If the chair is light and hardly braked, slave off before the modulator and let it lock. It solves the ABS issue under hard braking but not the general handling under normal conditions. For that you still need balance valves or matched components.

The solution is a 3S/3M system but that requires new software. I know guys at my former employers who could write this, but there is no way they'd turn it loose on the world untested. No one has the cash for the 5 days of track time and other bits a brake approval involves.

Are we bored yet? 

The good news is that so long as the red light goes off at some point a 4S/2M+1M select high ABS set up with software written by anyone who knows C+ would pass the MOT regardless of it's potential lethality  .

If we want a high tech solution, I'm suggesting EBS with a electric only circuit for the chair. Pot luck if they MOT that one with the ignition on or off 

Andy

[Andy M]

--------, VOSA's finest sidecar expert has retired! so they know FA

Oh, you just keep rubbing it in, why don't you 

Andy

[002]

--------, VOSA's finest sidecar expert has retired! so they know FA

But I know a guy that understands and knows a little.....He does MOT's 


Jethro

[guest1407]

Didn´t  quote…… 

Some 10 years ago I rode for the first time on a sidecar with ABS. It was a French built Zeus. As you know built with car components, for example a two liter car engine. The fourth ABS sensor was also put on the rear wheel disc. It worked. The system was fooled.

Quite common for the old Unit forks to have this kind of anti dive situation. The later ones don´t have it, because of the floating discs. When you have the brakes mounted directly on the lower part of the swingarm (it doesn´t differ if it´s above or below the arm), this will allways happen. If you want to built a floating system - a must imo - , keep in mind, that the connection rod should be somehow in line with the lower part of the LL.

Since I also prefer to ride in snow and dirt, I prefer the sidecar brake to be hooked on the rear wheel with just one pedal.
(For road use only, I can imagine to hook both the front and the rear brake to the sidecarwheel - with two calipers -  or even Guzzi style connect both front and rear).
 
The front brake is completely separate and not hooked to anything.  The right size of the main rear master cilinder with a normal rear disk and brake and a smaller caliper and disk  for the sidecarwheel, normally works out fine. Sometimes, depending on the bike, a larger master cylinder is needed.

The MZ outfit  I have (with the rear brake pedal above the pedal for the hydraulic sidecar brake) works too, but needs adjusting once in a while.  I suppose that works similar. Two pedals are imho not perfect, since you could hit the wrong brake in a unforeseen situation or with too large winterboots. Contrary to the front brake, you cannot foresee this.

As for MOT. We don´t have one for bikes. Dutch motorcyclist are supposed to know what they do.