Strange brake problem.

[Bob Purton]

Still doesn't make sense to me, all cars suffered sub zero temperatures this winter but there brakes didn't lock up. It was new dot 4 fluid last Autumn so I am also dismissing the hydroscopic influence theory. I'm going with the faulty master cylinder idea. The previous owner told me he had just fitted a rebuild kit, this was last summer so there must have been a problem before to necessitate the rebuild and now knowing the inaptitude of the last owner I am putting it down to the master cylinder.  If the problem comes back this winter I will have to eat a generous portion of humble pie which I'm developing a taste for!

[cuscus47]

Yes, I agree it is a perplexing problem.  .  I was thinking with my issue about the fluid being so old and with so much moisture in it, that it would freeze and somehow the extra pressure developed by the freezing caused the adjuster to operate.  Just as if you rammed super hard on the brake pedal.   I can see no connection between the adjuster and the slave.  So how is it possible?  And why not my front one?  These "Winter Brake Gremlins"  are tricky little urchins.  I am now thinking that maybe with seasonal use, somehow grit or dirt is settling on the cams of the adjuster, and thus tightening it over use, and with the limited use I don't notice the progressive tightening.  Then, over winter, the cams even expand more (30 below weather) and stick in a wide position tightening the brakes.  When I did clean these out there was gritty dirt in there, but they did seem to operate.  There is no protection for brake dust (or anything else) not to find it's way into this adjuster (open hole).  Maybe I should find a plug to fit them?  Anyway, after cleaning I did lubricate them well with dry graphite, so they should not stick, if that was the cause.  I did estimate the gap between the cams to be about 25 thou when operating correctly, but alas there is no way to measure when stuck, for you have to release it to remove the drum, to measure. Catch 22.  I don't think that your problem is the same Bob, but at face value initially did seem so.  Let's see if this thread restarts this time next year.   

[richard]

time we put a stop to this one ! or should we just let it fade aw...............

[Bob Purton]

Yes Ian. We will confer next March!

[Big Al]

Still doesn't make sense to me, all cars suffered sub zero temperatures this winter but there brakes didn't lock up. It was new dot 4 fluid last Autumn so I am also dismissing the hydroscopic influence theory. I'm going with the faulty master cylinder idea. The previous owner told me he had just fitted a rebuild kit, this was last summer so there must have been a problem before to necessitate the rebuild and now knowing the inaptitude of the last owner I am putting it down to the master cylinder.  If the problem comes back this winter I will have to eat a generous portion of humble pie which I'm developing a taste for!

Ah ineptitude. Very often the basis of a problem and sold to me as I spent much the last 25 years sorting that out on cars bought in. Funny how things work when assembled correctly 'innit?

[Big Al]

Can I just extend the discussion to Messerschmitt brakes. I have an unusual situation with mine. They work!

[marcus]

Can I just extend the discussion to Messerschmitt brakes. I have an unusual situation with mine. They work!

No they don't Al, it's just you pushing your clod-hoppers through the rust holes in the floor and pressing them down hard onto the road Fred Flintstone-style.

[Chris Thomas]

Dear Al

Congratulations

It appears to me that the brakes on Bob's Isetta also work well, infact the rear brake works too well.

As I see it, brakes are there to slow down and stop a car (under the control of the driver). I would be more disappointed if they did not stop a car from moving. The issue appears to be that Bob wanted his brakes to release under the control of the driver, which is the opposite of them working. Not unreasonable  when you think of it; especially as the front ones are releasing.

I am sure that with the engineering knowledge and skills Bob has all will be revealed in the fulness of time (next March)

Chris Thomas

[Bob Purton]

Ho Ho Marcus!  I think Al is having at pop at me for deserting the world of Messerschmitts for a brand of car he doesnt like. I think though now I have rebuilt just about everything on the car it will be a good un. I do admit that during the ten years I owned the schmitt it was very very low maintenance, all I ever had to do was adjust the brakes[frequently], change the oil and set the points but then again the car was restored properly in the first place! I miss the schmitt but not the vertigo attacks it gave me whilst driving it!

Thanks for the vote of confidence Chris but my "engineering knowledge and skills" dont extend to girling braking systems, mercury barometers yes! Theres a thought, fill the hydraulics with quick silver, now that WOULD respond to temperature change!!

[golo2]

Hi, still Paignton location, keen to know what actually failed! rubbers? bore scored? big lump of rust dropped in and circulated? is it still there? acting as a valve in the three way connector?
Forensic mechanics is of great interest to me. Easy to break stuff or inherit previous dubious quick fixes but real credible (safe) solutions of more interest
(recent broken schmitt track rod end springs to mind) nearly resolved with  thick track rods and real schmitt rubbers both ends and middle, just need to learn how to fit and time up new points

[Bob Purton]

I'm not really sure Ian. I dismantled the old cylinder and found nothing obviously wrong inside other than the fact that the spring was much weaker than the one in the replacement. It could be that the piston was not returning fully after being pressed in. Today I partially solved the steering wander, It turned out to be something that you mention earlier. The big center nut that holds the rear wheel hub on the splinted drive shaft had become loose, I have already nipped it up a couple of times but even though there is a split pin holding it , it kept coming loose. This time I thought I would really get it on tight with the use of a tube over the end of my socket wrench, I got it pretty tight but then suddenly I was able to give it about three more complete revolutions and could feel that the shaft was being drawn through the bearings inside the chain case until it came to a positive stop, it appears that the guy who rebuilt the chaincase had not drawn the shaft through the bearings fully, he must have stopped tightening the nut when it offered resistance, hence with use it kept moving. I immediately noticed an improvement with the steering, less wander. There is still some more improvement to make I think with a better worm and nut but all in all a good mornings work!.

[Big Al]

Might be pertinent to Isetta. Trienkels suffer from play on the rear axle. You would think that tightening it up, with the drum washer the correct way round, would solve this. It does not as the distance tube fitted over the axle to keep the two rear axle bearings in place either end of the casing but in tension is of poor quality steel. It therefore shears within itself allowing more play. Tighten it and a few months later it is loose again. Both Trienkel and Isetta rely on the splines of the hub to be a good tight fit to avoid rear steer. Clearly a sloppy rear bearing allows play and the spline is the weak bit. Once worn it is not easy to repair. So if you have a Treinkel sling the old tube and get one made out of proper steel to replace it. The club should sell these but historically refused to do so. Isetta owners take advice from someone who knows as they might have the same problem.

I like the mercury auto weather brake system. Fair weather, brakes work, can go out and play. Wet and windy, brakes seized, cannot go out and get the car wet.

Messerschmitts are renowned for the invention of the perfectly free functioning frictionless brake system possibly backed with ali brake shoes which only touch at either end of the friction surface when hot. Any Schmitter worth his salt has had to find himself parked on the pavement next to a line of traffic at a red light calmly looking over at them and going 'hi, guys. It's only me'. Further fun is peeing on the front wheels half way down a steep hill to get them working again, like going into Koblenz from the Autobahn Koln - Karlsruhr. So good are Schmitt brakes that they are at their most exciting when the car runs at its best, just after a rainstorm on a hot day. That bit of water vapour cools the charge and magnifies the power. Sadly the tyres do not grip well, or at all if cheapo boys, and the brakes rather crude on/off, well having thought about, off actually, nature can make for some very interesting experiences. Otherwise you drive slowly and the brakes are about adequate but that is really rather boring and you will be left behind by the pack on a run. Perhaps why Schmitts are not everyone's idea of transport as they do tend to suit the nutter element who have little time for dawdling.

[Chris Thomas]

Dear Bob

What would be the effect of using mercury in place of break fluid be?

Does Mercury boil at a lower temperature than brake fluid?

Would there be an electrolitic action between the Mecury and the Copper brake pipes, or the Aluminium Master cylinder components?

Would you ever need to change the Mercury?

Apart from weight, why have the Formula 1 racing boys never thought of using Mercury (apart from the health hazard)?

Chris Thomas

[Bob Purton]

Chris I was only joking! But as you ask, Mercury 674 F  and Dot4 dry 446 F but lower if moisture present. One advantage of using hg would be that it doesnt hold water. Disadvantages would be it would eat through copper pipe and eat the Cylinders out even quicker and then amalgamate. This could be solved by using stainless steel tubes and cast iron cylinders which I believe old ones were made from anyway. Would most likely last a long time too. Other disadvantages, its very expensive to buy triple distiled and heavy as you say. There is one other draw back that I can see and that is it has no lubricating qualities unlike brake fluid so it wouldnt work with piston rubbers.  Dangerous? This is scare mongering clap trap from our EEC friends, ok its dangerous if you drink it or boil it and breath in its steam! Then again so is brake fluid and a whole host of other liquids that that you can buy down the shops! The EEC have banned production of new mercury barometers other than for the MOD which fortunately has not effected the three surviving manufactures who will now make you a nice reproduction Daniel Quare and supply it empty. The customer can then hand it straight  back to them and request that they quite legally service and refill with this dangerous stuff there used/second hand barometer. What a load of nanny state clap trap! Someone at Brussels had to sit down and think about how to stop these three people from churning out all of half a dozen barometers a year that would be so dangerous. Meanwhile all our low energy light bulbs containing mercury get chucked into landfill by the millions every day! It makes my mercury, sorry blood boil!

[golo2]

the plot sickens!¬  I was always told that the rear nut you mention should be  F T  (second T=tight!!!!!!) any less and the splines will wear.

I use a long britool bar 1/2 drive and a length of tube also never loosen to get pin through castelated nut keep going on tightness. No doubt plenty of other advice will follow.

is there any rear wheel movement vertically or horizontally? maybe  splines or bearing!  there is a newer bearing that has a groove and a grease nipple can be added to the casting to enable extra lube  as the oil swishing around in the chaincase may struggle to get to the bearing ? comments welcome

pleased to hear from no one regarding my glass excess  as it means no one else has smashed bits!  Attic is calling.
Back soon  first show Abingdon week tomorrow