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Blue M
United Kingdom
1472 Posts |
 Posted - 29/02/2008 : 14:41:58
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Carrying on from the subject of fitting a J engine in an M type, is there anything that can be done to improve the M chassis?
Ian |
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sam christie
United Kingdom
3100 Posts |
Posted - 05/03/2008 : 23:13:03
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Ian, perhaps the chassis could be made less flexible by the addition of stronger bodywork ? Has anyone experimented ? I understand wood once did wonderful things for aircraft so perhaps wood and steel could stiffen a chassis ?
Sam |
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ht1962
Netherlands
114 Posts |
Posted - 06/03/2008 : 14:54:36
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Hello,
Isn't the somewhat high centre of gravity the biggest problem with the M type chassis.
Adding stiffness to the chassis won't change that so the cornering speeds will not get a lot higher unless you don't mind tipping over!
halbe |
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Blue M
United Kingdom
1472 Posts |
Posted - 06/03/2008 : 21:07:16
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Sam
I think wood has possibilities, although the chassis channel is not very deep. I tried twisting a length of wood this afternoon and found it just about impossible which surprised me.
Halbe, you are probably right about the cornering speeds although thats not what I'm after improving. I would just like to make it easier to drive on bumpy roads without having to slow as much as I have to now.
Actually it's surprising how quickly they will go round corners, the trick is to keep your foot hard down on the loud pedal. I think lifting off causes sudden oversteer. The centre of gravity is still low, even though not as low as Js etc as there isn't actually much to an M.
Anyway,keep those ideas coming!
Ian |
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davies
United Kingdom
699 Posts |
Posted - 07/03/2008 : 10:37:53
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| The bodywork obviously imparts an element of rigidity to the chassis frame if it is correctly mounted and of course rigid in itself.I have seen many M types without the bulkhead/chassis fixings for example. I have also seen some strange methods of fixing the door pillar angle irons to the chassis and even omission of the actual cross member at that position . None of which can help the situation. Regards Rich |
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David Allison
United Kingdom
665 Posts |
Posted - 07/03/2008 : 16:04:09
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The best way to improve the M chassis is to remake it.
This unfortunately detracts from the original car though - making it NOT AN M-Type!
The best way is to cut the rear of the chassis frame and re-jig the frame so that it is underslung at the rear.
Stiffen the front shackles and fit sliding rear shackles.
Re-jig the front end and fit stiffer front mountings by removing the swinging shackles and fitting sliding shackles at the rear.
MG did all of this in 1931-32 - the high peformance version of the M with a J type engine was called the C type and its successor the J type was introduced in 32-33.
Tuning M types is great fun but they are limited by the chassis frame, the high centre of gravity and being too short in wheelbase and too narrow, for their height.
The M type is therefore more prone to tipping over than almost any other MMM car and rather than spoil a good M type - I would urge you to be happy with what you have - a very good vintage sports car.
The M type was one of the best most affordable sports cars available from 1928 - 31 but improvements in that model were seen in the models that followed.
Mike Dowley, Mike Rushton and Clive Sherrif all had very quick M types, latterly Tom Dark and Frank Ashley too have gone very well.
Alex Peacop's 12-12 is very quick and there are others - but try too hard and over she goes.
I had experience of a very well developed M type specialwith a C type (AA Head) engine and that was more than too fast for its chassis in my humble opinion.
By all means try - its been done before - but it will end in tears!
Regards David |
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Blue M
United Kingdom
1472 Posts |
Posted - 07/03/2008 : 22:14:47
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I think that Rich is on my wavelength with this one. Making a Special is not something that really interests me, nor do I aspire to the ownership of a J type ( too heavy and no boot! ). I happen to think the tipping over aspect of M types is overstated and also that the slightly greater chassis height works in its favour on a wet bend.
I think integrating the body structure is the key to stiffening the chassis and thus making the car more easily controlled. The other week I noticed the unlikely similarity between the M chassis and a VHS video box. When the lid is open the box is completely floppy and unstable, and when closed it is completely rigid. I started to wonder then about how to incorporate the floor panels with the chassis frame in order to make, in effect, a stiff box between the two middle cross-members. I think solid lengths of wood bolted between the floor and cross-members might be enough, and would also do a bit towards preventing the cross-members twisting ( which they do ).
I already have the petrol tank at the rear below the boot. I find that I do in fact look through the windscreen rather than over it, although I have to slouch down a bit when the hood is up.
I certainly don't think , as David suggests, that the best way to improve an M chassis is to to change it into a J, and I don't think either that they are too short and too narrow for their height( it was after all originally a 4-seater chassis) and the shackles are not the hopeless things they are made out to be - far more MGs have been made with shackles than those brass sliders.
The chassis was probably ok in its Morris guise as all the Morris bodies were quite substantial and much stiffer than the little Midget.
Does anyone know whether 12/12 cars had different springs - I know the dampers are bigger.
Ian |
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kimber
United Kingdom
1529 Posts |
Posted - 07/03/2008 : 22:38:34
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quote:
Originally posted by IAN JUDD
I happen to think the tipping over aspect of M types is overstated.
Ian
The best example of this was demonstrated at Silverstone some years ago. They will readily and suddenly invert if hard-pressed.
Another one was quite spectacularly rolled during my father's ownership. The photo shows the car a couple of weekends later at a sprint meeting with makeshift 'birdcage' bodywork constructed from electrical conduit. Those were the days. (The car was affectionately known as "Hairy Mary").
http://farm4.static.flickr.com/3103/2316775279_8c16471612.jpg?v=0
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Edited by - kimber on 07/03/2008 23:41:31 |
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Blue M
United Kingdom
1472 Posts |
Posted - 07/03/2008 : 22:53:34
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Hi Kimber
Just looking at your photo shows that it can hardly be described as a high car. Personally I am very suspicious of the front dumbirons, they are amazingly flexible and I think they bend under load. I have fitted a front cross-tube in the hope of reducing it. Don't know if it works though - not really the kind of thing you want try on the open road!
Ian |
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Cymber
United Kingdom
966 Posts |
Posted - 08/03/2008 : 13:05:27
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Talking of stiffening front dumb irons. I believe Ramponi fitted close fitting wooden inserts into the Seaman Delage dumb irons in the early thirties for just this reason but I don't know how effective it was. Might be worth a try as it's not a permanent mod.
Maurice Blakey. |
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David Allison
United Kingdom
665 Posts |
Posted - 10/03/2008 : 13:19:11
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Before reading this - scroll down you might regret it!
God this is so long now I dont think anyones going to read it!
I really think that the M type is best looked at as a child of its own time.
In 1928 it was revolutionary - by 1931 it was old fashioned.
The M chassis is too flexible - that is why they re-designed it.
The standard body does not add a great deal of extra stiffness - the 12/12 car was a step forward though.
In 1928 the M type was a very able and well designed sports car.
In comparison to the 1440 the car was nippy and lightweight with great handling and road holding.
By 1929 the car was becoming dated - experience gained at the JCC relay showed that the car was suspect in tight corners and prone to tipping up on to 2 wheels.
This led to work by Reg Jackson and his team on the 12/12 car ready for the 29 race.
They increased the spring rate and fitted a body which was lower set and also made attempts to lower the overall centre of gravity.
The car was not a great success - it was quite expensive and rather heavy and the Austin car it raced against benefitted from a better handicap (thanks to a smaller engine) and was nearly as fast (thanks to lower weight).
Fortunately the Austins were not terribly reliable and the M types performance was good enough to gain a very good result.
Unfortunatley the result sounded the death of the MK3 (Tigress) which was too slow and too heavy.
The M was not really suited to international racing (the 850 engine was too large for to race against the Austin)and it was decided to accelarate the EX 120 project.
EX 120 was started as an M type.
The engine was progressively tuned by Reg Jackson but they encountered the problems with the cars cornering ability.
The D type chassis was a good deal stiffer than the M.
The centre of gravity was even lower than that of the 12/12 car and lessons were being learned about chassis stiffeness.
EX 120 was built as a development for the new model - but the work on that model centred on the need for a 750 cc racing car.
The result was the C type - this car was lower, lighter and faster than the 12/12 car and had a 750 engine.
By 1931 the M was seriously long in the tooth and they started work on a road going version of the C type - the J2 was again stiffer and lower than the M type.
As I said in my original reply - there have been a number of very quick M types and specials.
Terry Dickie had a very nasty roll-over at Silverstone in his 12/12.
Tom Dark had his M on two wheels a number of times although I am not sure if he actually managed to tip it right over?
Mike Dowley and Mike Rushton both had very quick M types and managed to keep up with J and P types - even finishing ahead a number of times. But I think they would also say that for really quick cornering - the M type is a less than ideal starting point.
Clive Sherrif had a very quick M type single seater.
The car was stiffer and lower than standard though and very light weight.
Nigel Musselwhite built a replica of EX 120 - but this car used a D type chassis.
M types can be made to go very well but ultimately the excercise might end up producing a car which bears little resemblance to an M type.
The Skinner Special started off as a Morris Minor - the car was progressively tuned and got faster year on year.
However when the skin was removed the car looked more like a D or J type chassis than anything produced at Cowley.
I just think that we are re-inventing the wheel - the result of which will end up looking rather like the wheel it self.
Ramponi did indeed stiffen the chassis of the Delage - ultimatley having a new stiffer boxed steel chassis made for the car.
The wooden inserts were a pattern fo rthe fabricators to make up the inner rails.
The Riley TT sprite chassis is boxed as is the C and D type ERA.
I think there are a number of MMM chassis that have been stiffened in this way too (the Parnell K3 was done pre-war).
In each case this was to increase chassis rigidity and reduce sping rates to reduce the tendancy to lift wheels mid corner.
With the ERA and Parnell K3 they had fitted IFS and needed additional stiffeness to make the best use of the independant springing.
Unfortunately the result is a heavier car with very little improvement.
The increase in chassis rigidity is minimal - the issues and handling problems are actually more to do with a major failing in ladder frame chassis rather than anything else.
Beam axles do nothing to improve things - when 1 wheel starts to lift its axle pair will drop - thus multiplying the negative and making the problem worse.
Alec Issigonis built a car using an Austin 7 as a donor car.
Called the Lightweight Special - the car was a modern monocoque built from aluminium honeycomb and plywood sections clothed in a stressed aluminium bodyshell.
The car was incredibe on many levels - the chassis was around 100 times stiffer and less than a 1/4 the weight of a car with a ladder frame.
The car was able to make proper use of its independant springing - each wheel being almost totally independant of its axle pair - because it had no axles.
Unfortunately the war got in the way of its development for a few years and after the war materials for this kind of manufacturing process were scarce.
Issigonis and his team continued to work on the construction idea - using steel instead of aluminium.
All modern cars are built in this way - now using developments of the work carried out by Issigonis and others.
Everything I have said has been said before - by all means build an M type with a J engine - just be carefull not to make the same mistakes of others 80 years ago.
The chaps who designed and built the cars knew a lot more about engineering than we give them credit for - if the M type was indeed a good starting point - they would not have developed the J type or P type.
They spent 2 years development on the M type trying to make it go faster - the result was the J type and I think that is where we will end up too!
God this is so long now I dont think anyones going to read it!
Regards David
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Bob Hudson
United Kingdom
67 Posts |
Posted - 10/03/2008 : 21:51:28
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David
Thank you for your very thorough exposition on the M type improvement question. I think that may put the discussion to
bed or mey be not!!
Bob H
PS I have read every word twice!! |
Edited by - Bob Hudson on 10/03/2008 21:52:21 |
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David Allison
United Kingdom
665 Posts |
Posted - 11/03/2008 : 14:56:04
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Thanks Bob - what sad lives we both lead (me for writing - you for reading).
All the best David |
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Blue M
United Kingdom
1472 Posts |
Posted - 11/03/2008 : 18:15:22
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Andrew, and just about everybody else, feels that " the M type will readily and suddenly invert if hard pressed". So, can I put my original question another way?
What can be done to an M that might slow down the suddenness of this, so that the driver has time to do something about it? Could it not be even a simple thing like tyre pressures?
Sorry to keep banging on about this, but I'm not wholly convinced by the " the manufacturer knows best" argument, particularly when that manufacturer has had more exciting projects on the go.
Ian |
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sam christie
United Kingdom
3100 Posts |
Posted - 11/03/2008 : 22:01:27
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I think Ian's question is a really good one, for another way of looking at it is to ask the very basic question - How can I optimise safety fast while remaining true to the original design ? And presumably safety fast means greater safety at lower speeds too ?
Sam |
Edited by - sam christie on 11/03/2008 22:02:50 |
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David Allison
United Kingdom
665 Posts |
Posted - 12/03/2008 : 12:54:46
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To slow down the suddeness of the problem caused by a chassis that is too flexible and springs that are to soft is as follows.
First stiffen the springs - this makes tipping over more likely.
Second make a different chassis.
I am sorry Ian but you are missing the point here.
The factory did not abandon the M type nor was it a case of "manufacturer has had more exciting projects on the go" - the next progression from the M type was the J type.
The M type is relatively stable in standard form - it becomes more likely to tip over as the cornering demands increase.
Sharp cornering at any speed can cause an M to 3 wheel and 2 wheel quite alarmingly - at high speed the tyres tuck under and literally flick the thing over.
Ian - it is time to accept that - indeed the manufacturer did know best - they developed the M type tirelessly over 4-5 years from 1928-32 and the car was very successfull.
But one thing the car ain't - it ain't a racer and never was!
If you want to disprove me - please do - just make sure you have adequate insurance and medical cover available the first time you do.
Best of luck - all my comments are based on reading contemporary reports - being there when M types have needed re-riting and helping nurse those who have bruised their egos when denying the inescapable fact - THE M TYPE IS FAST ENOUGH IN STANDARD FORM.
I am bored with this particular post! |
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