Microcar design faults.

[Bob Purton]

I thought it would be good to confess all the design faults we have discovered on our beloved microcars, not so much to mock but just out of interest and to give others the heads up. Lets face it, all microcars have them.

I will start.
The two Isetta's I have owned.
Leaky exhaust manifolds making the cab a little fumey at times.
play in the steering mainly due to worn bronze bushes on the link shaft. RHD cars don't seam to suffer so badly as the shaft is much longer. Hard to work on. Lots and lots of parts!

Point I like..... Sociable side by side driving, nice big sunshine roof, decent suspension, bullet proof gearbox. Excellent brakes.

My old KR200.
Terrible ride due
 to tiny wheels and rock hard suspension.
Cant open the engine cover to tinker unless the whole canopy is open so if doing so in the rain the whole interior fills up with water and also soaks passenger.
Weak gearbox, prone to jumping out.
Hard to drive in a straight line.
Roasting under the plastic dome. Heat from sun in certain positions even melted the upholstery.
Brakes tend to fade.
Poor engine castings, clutch bearing breaks through casing.

Points I liked....
Fun to drive [until I started suffering with vertigo!] because quite nippy and agile.
Simple design, easy to work on.

Bond MKC.
Very poor brakes.

Points I liked.
Just about everything!
 

[Big Al]

In defence of the KR200

The suspension is hard, but without it you would not get the sporting handling. New rubber makes a huge difference. But it is hard compared to most.

Hard to drive in a straight line? - when not set up correctly, not rebuilt correctly or on cheap tyres. Just try a set up car and you will find it hardly deviates unless on a cambered road. It goes where you point it. I would suggest this one is an own goal. Its bad side is deviation from gusting wind. Stuart suffers from that too, after my curried Brussels sprout soup.
 
I would not call the engine casting poor. The issue is its a modified 150cc engine and has a poor clutch design in its entirety, really due to use of the same 150 gear cluster, which is also inadequate for 50 years service. However the car was made to last, possibly, 5 years. It performed excellently within its design perimeters, which now look very limited. The clear path forward is shown by John Bannell's Frankenschmitt which resolves most of the issues mentioned by use of better brakes, a bigger and stronger engine and a slight alteration in the suspension.

Other irritations of the Schmitt

Loose front seat, where the rivets get play in them.

Cracked steering bar. Not a safety issue as the steel inside must be whittled off a Tiger Tank. Its is some of the hardest steel I have come across! Its just an unsightly, but commonly seen, problem.

Lack of fuel pump. Even a low pressure pneumatic pump would improve the performance, with modern fuels particularly.

Brake cam design.

Some of the owners!


Isetta, additional

Wieght, they are heavy blighters.

Poor use of space

Poor layout of some components making for access issues or additional weight that could have been saved.

Poor front suspension geometry and execution. Over complicated, to many joints

Gearchange like stirring porridge on most. Over complicated, to many joints

Rear drive friction. Over complicated, to many joints

Yet made down to a cost so some materials used little better than case hardened cheese. What other car has cylinders that brake in half? Valves that fall appart unless replaced with properly manufactured ones.

Slow for its engine size.

Better competition? Could have been but for its own probs. Because BMW threatened to sue all potential competitors some did not invest in redesigning their faults out but moved production to beyond litigation. So many faults on some other cars are because of the Isetta!


Bond - additional

Tyre wear on front. The one wheel does most of the work. 

Fixation on small doors. Not the only Brit firm to do this!

Barking whippets

Possible too eccentric to ever be the success it deserved to be in its time.

Reliant on Villiers to produce the good engines they eventually came up with, but by that time they had lost the best of the styling. The favourite, most wanted modern Bond was never made by the factory. A 250cc Mk C/D Tourer.

No slow running cooling/fan, no heating.

[Bob Purton]

I guessed that would trigger a mammoth response from Al!!

All good stuff Al and I wouldn't dispute any of the Isetta knocking although I have never heard of cylinders breaking in half?? Exhaust valves on the Brighton ones, yes.

To qualify what I said about schmitts having poor engine castings, I didn't mean definition in execution, just the fact that the alloy that Sachs used was utter rubbish. If you don't believe me try welding a Sachs casting and then try the same on a British motorcycle casting of the same period. The Sachs one will spit something dreadful because of all the impurities in it whereas the British alloy will behave and weld admirably. Maybe this is why the clutch bearing flange gives way??

Funny you should mention a Bond MkC with 250cc engine, that's exactly what mine had fitted, went very well.

[richard]

but did it stop ! perhaps this is why you rated he brakes poorly ? 

[Daniel Rodd]

Bond 875,how it was ever allowed on the road baffles me

[richard]

daniel , list the design faults to help us out

[Daniel Rodd]

Front end lifting over 50mph,no rollover strength whatsoever,minimal strength in the body and floor,a front end that pulls to one side when braking,and the other when accelerating,fuel tank located in a prime shunt location etc etc.

[Rob Dobie]

Bond 875,how it was ever allowed on the road baffles me

You could say that about some of the drivers about nowadays.

Nobody want to rate the Peel P50?  My old MHX 90C had the rear wheel chassis mountings 2" out of centre, that's why the lady owner fell over in it.
The other design fault I found in 1976, there was only one sliding window, absolutely useless when puffing away on my pipe and ciggies. I couldn't see out to the rear view mirror.   

[Bob Purton]

but did it stop ! perhaps this is why you rated he brakes poorly ? 

No Richard. I had a 197 powered MkD shortly after and the brakes were just as bad.
Now your turn to list the faults of the Gordon, I wonder if that pulled to one side under acceleration? I say acceleration in the loosest sense!

[richard]

  the car is in no fit state to tell but i will post some of the period reviews on that matter and it never appears to have caused a problem . see also NEXT RUM magazine - i am ahead of the game this time 

[Big Al]

To qualify what I said about schmitts having poor engine castings, I didn't mean definition in execution, just the fact that the alloy that Sachs used was utter rubbish. If you don't believe me try welding a Sachs casting and then try the same on a British motorcycle casting of the same period. The Sachs one will spit something dreadful because of all the impurities in it whereas the British alloy will behave and weld admirably. Maybe this is why the clutch bearing flange gives way??

The die casting does not break unless by outside cause or a crank failure. So there is no reason to weld it. The clutch bearing lip tends to fail as the engine is missassembled at some time and the lip stressed. There is a repair insert available that needs no welding. Strangely the case is stiff and accurate enough not to leak oil or air.
But the clutch is a poor unit and barely strong enough for the job.

[Bob Purton]

I have handled three of these engines so far with broken clutch bearing lips, I have no way of knowing if they had been "misassembled" in the past but if they had or if they had not it does highlight a design fault. The poor quality of the alloy cannot help surely? My impression was that it was the constant force of the clutch in operation that weakened and eventually fractured flange. The entire pressure of the clutch opening and closing is pressing against a flimsy alloy lip. Very poor design in my book.

[Bob Purton]

Moving on to Frisky's,
I'm not an expert but wasn't there some design fault in the front suspension? I think it required a modification.
awkward to get into due to the position of the doors in relation to the inner wheel arches as I remember.
Brakes are over sensitive.

I owned a Family three with a Villiers twin engine briefly and in general thought it was a great little car.
I liked the steering and the performance.

[Big Al]

I have handled three of these engines so far with broken clutch bearing lips, I have no way of knowing if they had been "misassembled" in the past but if they had or if they had not it does highlight a design fault. The poor quality of the alloy cannot help surely? My impression was that it was the constant force of the clutch in operation that weakened and eventually fractured flange. The entire pressure of the clutch opening and closing is pressing against a flimsy alloy lip. Very poor design in my book.

The bearing is fitted into the housing using heat. It is a friction fit. The lip is to locate the bearing in the correct place. In the same way that a woodruff key is there to guide and position a dynostart flywheel. The taper does the holding of it, not the woodruff key, which is in fact made to be sacrificial, unlike the clutch bearing lip.
Welcome Mr Hammer and Mr Whatsa - Shim. Either rebuilding a Sachs engine, its German remember, so you think engineering, is going to cock this up. Hammering in the bearing means it will damage its friction fit. It might fracture the lip too. Not shimming is to have a loose layshaft and a miniature slide hammer. To much shimming or a needle roller bearing fall over during assembly means the shaft is to long and will push the lip out. The engine is made to be built by people who understand it. Made well, it works well. Wynford, and others I do not doubt, have a selection of tools and a half crankcase to aid them shim up the engine. That is why Wyn, Nick, Pete etc get asked to do the engines.

This is not a design fault, but operator error. The alternative is to say its not idiot proof.

The design flaw is the clutch itself. The basket is to weak, I can bend it with finger and thumb. Even the later double drive plate noshs the edge of the basket up. The clutch bearing is an eccentric design and likewise weak. The central bush can get stuck and wear its end off. The 9 compression springs become weak, up the power and they begin to struggle to provide grip, to the extent plate kits exist to add 3 extra springs. (Not helped by the stronger springs being unobtanium for years and the Moped springs being substituted as it looks the same but has not the stiffer rating, so fails quicker under load. Not sure if this sourcing issue has been resolved).
There could have been a nice forged basket using standard bearings. Sadly you get a modified 150 system that does rather limit things. It is often the part that wears out first and a worn clutch can take out the gears, as they become loose, and also the casing lip. That is not the lips fault. Such a worn item should have spotted by a owner who is responsible and maintains his car as folk used to. You want to live in a service every 10,000 miles world, then do not buy a Messerschmitt or be prepared for a large bill for your ignorance.

[Big Al]

Frisky - Ooo eck. Get into trouble.

THe strut was original fixed to the GRP moulding and thus could not flex, other than by stressing the GRP moulding, as I recall. Later it was mounted in a better way so it could move. The rear mounts on top of the 'boot' still have great opportunity to stress crack.

Some doors were made so they went right into the wheel arch. This found water and crap geting in the door edge. So some cars have doors short of the front wheel arch.

Indeed much Frisky work seems to have been on the suck it and see basis. But at least they reacted to errors of judgment unlike some productions. I cannot comment on if this additional cost of continual improvement of design hastened the cars failure. The whole manufacture of the car seemed to be damned by internal politics and infighting. I think that was perhaps more of a failure than the car itself!