Building and Racing the ESC 750 – 1981 & 1982

Everything you need to know if you are thinking about racing in 750 Formula

Building and Racing the ESC 750 – 1981 & 1982

Postby EmlynC » Tue Feb 21, 2012 11:16 pm

I raced in my own 750 Formula car 1981 and 1982, and, having seen Martin Kemp’s car at this year’s Autosport Show, decided to come back and look at building a new “transverse” Mk 2.

At the end of my first season I wrote the following article for the December 1981 Bulletin, which I think still has lessons that would be useful to someone starting out for the first time, and it is also interesting to compare costs with today.

I have also added notes in italics to the original article, and an extra section to cover my second season, which ended against the Armco at Silverstone.

Introduction

Since the age of twelve, when I bought a 1934 Austin 7 for £5.00, I have wanted to build my own 750. Over the past eleven years I have slowly collected and made the parts required, and spent the last six years building the car that first raced at Lydden Hill on 31st May, 1981.

As such a project is full of pitfalls, the following article will try and pass on some of the experience gained.

The first point to make is that if going racing is the main reason for building your own car – DON’T! Buy a second-hand car and learn all you can, then design and build your own racer. The reason is simple, it takes many hours to build a good car, and more money than you estimate. A good guide is to work out all the costs you can think of, double this figure and add £500 (need to treble all quoted costs to allow for inflation to 2012).

My main motivation was to build my own car to the highest standard that I could achieve with the funds I could make available, while making as many parts as possible in my garage (and it will be the same again this time).

Development of the Design

I strongly believe that before you start cutting metal you first need to assemble the key components round you – engine, gearbox, back axle and maybe the front uprights, and then start working on the drawing board. (Do not buy the wheels and tyres at this stage, only get detail of the overall sizes and work with these – I have eight year old tyres that were the ultimate when I got them and are now totally outdated.)

My basic parameters were:
1) Relatively conventional front engine design
2) A stiff space-frame chassis
3) Independent front suspension
4) Longer than average wheelbase
5) Very comfortable driving position
6) Low frontal area
7) Attractive and well presented

Assuming that you are going to build a space-frame car, the next stage is to start to make 1/8 scale models of the chassis out of 1/8 inch square balsa wood; this will quickly give you an indication of how stiff a structure you have designed, and where you need to add extra diagonals (I know that we had no computers back then, but I still believe that this a very valid thing to do, and have already started constructing my first chassis model this time round).

One thing I overlooked at this stage was that once the car is finished you must be able to work on, and change, major components easily – I have to take the engine out to remove the gearbox and disconnect the rear suspension to change the diff., both of which waste limited preparation time. (For the second season more of the body panels were made removable, and that really helped).

My next stage of development was to build the frame full size in wood cut exactly to the outside dimensions of the proposed tubes. I am sure that many people would consider this a waste of time, but I believe it was invaluable in determining if all the major components, including the driver, would fit. (It is great to see the photos of Nick Mantis doing the same thing now, despite his extensive use of computers in developing his ideas.)

I ended up building a second wooden frame, just because I would not fit into the first design comfortably. I spent hours working on the relative position of the controls, and the position of the engine/gearbox is purely determined by the ideal position for the gear lever relative to the seat position. The final result is that I now find the car totally comfortable despite its small size.

Before the frame design is finalised ensure that you have determined the exact position of all suspension mounting points. I changed the top front suspension pick up points after work on the frame had started, and I now have a very compromised solution which affected both the frame and the body mouldings. What I considered such a compromise at the time is almost the same as the mounting points on Martin Kemp’s Falcon, so maybe I was not that wrong.

About the time I built the second wooden mock-up I was very fortunate to get to know Keith Messer, who lived locally. Since that time his advice, guidance and encouragement have been a vital part of the whole project.

It was Keith who set the parameters for the front suspension design:
1) Constant roll centre
2) Constant track
3) Limited camber change
As it is an area where compromises have to be made, the following points were also considered:
A) Bump is more important than droop
B) The roll centre must not move up
C) Roll centre is more important than track

I then spent many evenings working on full size drawings plotting different wheel movements, and every time I got two out of three to work Keith would tell me to try again until all three worked together.

The final design ended up with:
1) Roll centre remains constant on bump at 7/8 inch above the ground, and rises 1/8 inch to 1 inch when the wheel droops 2 inches.
2) Track remains constant on bump, and comes in 1/8 inch each side on full droop
3) Camber changes 1 degree per inch of wheel movement.

Constructing the Frame

The frame was brazed up on Keith’s workshop floor, having first set up two RUJs as a dead level base. As some very large forces can be generated at this stage, each tube should only be tacked in position until all the tubes are in place. I had earlier built another frame without knowing this, and not only did it twist, but the stress on a 1 inch square tube against the 2 inch side members was such that a 14 inch crack appeared in the side member – one frame scrapped!

The frame was mainly constructed from ¾ inch square 18 swg tubes, with 5/8 round 20 swg tube for the diagonals. Where it was clear that there would be high loads (rear frame and the tubes that carry the engine) 1 inch 16 swg was used. Major brackets were then fabricated out of 16 swg sheet, and less important ones out of 18 swg. Fabricating brackets, while time consuming, is really very simple. You first require some ½ thick steel, from which you cut the shape of the bracket required; the edge on one side is then filed smooth and given a radius (1/16 to 1/8 inch). The bracket should then be marked out about 1/8 inch larger than the former shape all round, plus allow extra material on the base to clamp it to the former. Using a light copper mallet the edge of the bracket is them folded over the radius on the former. After cleaning up with a hand file, the end result is both light and stiff. All suspension mounting points were turned from solid steel rod and pass completely through main chassis tubes.

Bodywork

To produce a really professional looking car, I consider that it is essential to make the main bodywork in fibreglass. In my own case the nose and top body panel represent about 500 man hours (Emlyn hours!). I made the mistake of producing the two elements separately, and to get the best possible visual balance all elements should be developed as one. The plugs were constructed from ½ inch chipboard and 1/8 hardboard, while all the double curvature elements were built up with “Polyfilla” (no plastic foam available back then). The plug for the top mould was built on the actual chassis with a Reliant engine in place. After the overall shape had been formed, using a Surform plane, the hard work started. I first let the plug dry out, and then sealed it with “Release Agent A”. This was followed with 20 coats of primer/filler, which was rubbed back after each coat. Different colours were used to show just where the high points were. When finally finished I let the paint dry hard over 3 to 4 weeks. The plug was then given 10 coats of slipwax, which was put on sparingly, slowly building up a surface. “Release Agent B” was only used in areas where there were difficult returns as it always leaves streaks. I always leave any mould which has been slipwaxed 24 hours for the wax surface to harden before moulding. The reason for all this care at this stage is that it is possible for the fibreglass to stick to the plug, and all the hours of work are then lost. (My first full width nose ended that way!)

I suppose that I should have also talked about making sure there is enough of an angle on the mould, or to split the mould by using an aluminium former cut to fit the required shape of the plug, and then held in place with plasticine on the side not to be moulded first. Once the first part of the mould has been moulded, the aluminium is removed and “Release Agent B” applied to the exposed return surface. The second half of the mould can now be produce so that you end up with the two return surfaces together. Once the second part has cured, the returns can be trimmed to a height of 50-70 mm, and then drilled so that they can be bolted together in exactly the right position for the moulding of the actual panel.

The Engine

I cannot claim any special knowledge in this area as until the last two races of the season I had never seen more than 7200 rpm in top gear. At the SUNBAC Meeting at Silverstone, Dick Harvey lent me his spare head for the race, and this one change transformed the performance. I therefore quickly produced my own head following the lessons learnt for the final meeting at Snetterton.

While there was still a top end misfire, I am convinced that I now have the basis for a competitive engine for next season.

The specification of the final engine (after five compete re-builds this season) being: -
Block: 700 fitted with 750 liners, lighted A series cam followers, steel strapped main bearings.
Head: 750 with some work on the ports, welded core plug and 80 thou machined of the face.
Camshaft: Piper 2 RER 2
Crankshaft: 600 type with 10 thou undersize mains and standard big ends (Vandervell bearings)
Flywheel Specially produced aluminium flywheel with steel insert for the Imp clutch
Rods: Standard, but carefully balanced
Pistons: Set of Ron Welsh racing pistons, all exactly the same weight. Gudgeon pins held in place with PTFE caps
Lubrication: Dry sump using John Village castings, and front mounted pump driven off the camshaft – gives a constant 80 psi using Castrol R
Carburettor: Dellorto FZD 30/24 fitted with 22mm restrictor, mounted on a Haque/Messer inlet manifold.

There are a number of points that are important:-

1) Always build up any new engine around an unraced block (or one that you know the exact history). Check that it is not twisted by fitting a straight crankshaft and see if it will turn freely by hand. I purchased one of Richard Owen’s mandrels and scrapped the bearing surfaces on my first block to make the crankshaft turn freely – I suspect that all I was doing was putting off replacing a twisted block. Many of the front runners replace their blocks at the end of each season, even if they appear to still be OK.
2) If you are using one of the 60 thou head gaskets that Dick Harvey can sell you, machine the top of the block to allow the pistons to come 20 thou out of the top of the liners to keep the compression ratio up; (it is possible to go to a maximum of 40 thou).
3) There is very little to be gained by increasing the compression ratio over 11/11.5 to 1. Bob Simpson only uses 10.5, and there is very little wrong with the performance of his engine!
4) Very large ports and valves produce negative results.
5) Ali push rods are a waste of time.

Gearbox

The gearbox is fitted with a set of Newman close ratio gears which have worked perfectly, and only required one routine oil change all season.

Race Record

Up until the last two races of the season I had been disappointed with my results; I had not managed to develop the car into a mid-field runner, which had been my aim for this year.

The season can be summed up as: Retired on the grid (head collapsed); Last; Last; Second from last; Third from last; Fourth from last; Retired during practice (rear main bearing cap bolt failed); Retired during the race (very bad misfire); Seventh from last; Ninth from last.

The final meeting at Snetterton was the highlight of the season. I was on the twenty second place on the grid, but Keith made some detail changes to both the engine and chassis before the race.

In addition Dr Mike Bott used some sports psychology on me before the race. He came over and said, “Emlyn, your car looks brilliant and you have used all the right bits, so why are you driving so slowly? When you are on the grid this afternoon, Think Tiger.”

I’m not sure which had the greatest effect, but I was six seconds a lap quicker in the race than practice

At the end of the first lap I was at the back of a group of five cars consisting of Ian Bates, Peter Bradbury, Jim Tegerdine, Nicholas Bullen and myself. After a really close scrap which lasted for the complete race, I was leading the group, finishing in eleventh place overall. Although it was my tenth meeting, it was the first time that I had actually “raced”, and I found it tremendously exciting!

From my very first meeting I have kept detailed records. These include weather conditions, engine specifications, chassis settings, problems experienced, lap times and results. This file already has a vast amount of data and is a vital part of the overall development programme.

Following the last race I was asked to exhibit the car on the Club Stand at the Milton Keynes Racing Car Show. I consider this to be a real honour, and it has allowed me to put a little back into the Club, which I believe is very important.

Development Programme for the Winter

This winter will see a number of major changes made to the car; these will include a change to 13 inch wheels and a set of new G65 Goodyear tyres, converting both front and rear brakes to discs. Changing the chassis to allow greater rear axle movement. A careful look at all components to see where weight can be saved; total weight is 318 kg at present. Setting the engine up on a rolling road. Building a spare engine and gearbox. Moulding a new shape for the nose.

Costs

I have kept a full record of every expenditure on the project, and can therefore give an exact breakdown of my total costs to date. I’m not trying to impress anyone, or buy the Championship, but I do think that it is important to give anyone starting such a project an indication of the true cost involved. I know that it can be done for less, but I do not think that with my limited experience, and the standards that I set myself, I could have saved much.

Total cost of the complete car (spread over ten years) £2,800
Trailer £750
Helmet and overalls (present from parents) £400
Parts during the season £675
Parts for the winter re-build (so far) £240
Licence and entry fees (2 practice days & 10 meetings) £260
Petrol (road and race car) £140

Total £4,790

Despite having spent far more than intended, I do not regret any of the money invested on the project.

Conclusion

Finally, I would like to thank all the people who have assisted in allowing me to have so much fun, firstly building the car and then driving this season. They range from my family to all the people who give up their weekends to organize and marshal events; all the people involved in the Formula who all manage to combine competitive racing with a very friendly atmosphere in the paddock. And last, but certainly not least, Keith Messer – without his help it would not have been possible.


Additional Notes written February 2012 (based on the records from 1982)

After the season was over I took the car to Goodwood to try different nose and wing combinations. All other settings were left alone so direct comparisons could be made. The results were:

Full width nose with wing – 1m 47 sec , max rpm 7600

Narrow nose with wing – 1m 48 sec, max rpm 7200

Narrow nose no wing –1m 45 sec, max rpm 7200

Full width nose no wing – no time set as the car was almost un-drivable.

Returning to the original set-up produced the best time of the day – 1m 43 sec.

In total covered 70 laps during the day (166 miles), with no mechanical problems.

Jem Marsh Award

At the end of the year I was delighted to learn that I had won the Jem Marsh Award for the best prepared car; something I’m very proud of and the cup is still on display in my dining room.

1982 Season

My first race in 82 was at Thruxton in May. During the winter the chassis was totally re-built with 13 inch wheels (10 inch in the first season), disc brakes all round (had been drums) using lightweight AP bike calipers, removable steering wheel (brilliant), converted a number of body panels to be removable rather than riveted, and lightened components (overall weight reduced to 313 kg). As the engine had run so well at the final test at Goodwood, the only thing I did over the winter was check and re-build the head – it was just about to be an expensive mistake.

I had not had time to finish the new nose, or build the spare engine and gearbox.

In practice I was eighth fastest, and by lap three I was up to sixth (this year I would count from the front of the field). Coming past the pits there was a massive grinding sound and lots of sparks and I coasted to a halt on the outside of the circuit. The crankshaft had completely broken across the rear main journal, and the flywheel had travelled backwards into the bell housing! Almost every part of the engine was damaged, and I would not be out running again until the beginning of August, as I had not built the spare engine.

At my third race of the season, at Lydden Hill, I just qualified for the fast race, and finished in eighth place – my very first, and so far only, championship point!

The notes for the fifth race at Castle Combe say, “Raced with Alan Avery, best lap 1min 21.9 sec. Most exciting race of the season. Finished 12 out of 19.”

I did one more race at Cadwell, and then took the car back to Goodwood. For the first time Keith drove the car, and he quickly identified that the car wanted to oversteer on fast corners, and suggested harder front springs, softer rear springs.

These were fitted for the final race of the season at Silverstone. Practice was at about 9.00 am and the track was damp after overnight rain. I went out and instantly knew that the car had been transformed. It felt brilliant, and all that I had ever hoped it would be. It felt as if it was glued to the road, and gave me a level of (over) confidence I had never had before. On the second lap I was flying, and felt certain that I could easily pass on the outside three cars as we took the original Woodcote corner on the club circuit – a very wrong move!

I got about half way round the corner, and then the car just broke away and very quickly went onto the very wet grass, which did nothing to slow it down. I was still travelling fast as I hit the Armco at about 30 degrees, the back then swung into the barrier and I then started spinning back towards the track – I greyed out, which happens above about 4.5 g, and can remember pressing pedals hoping that I would stop before being hit by someone coming round the corner.

The car was a mess, with only one wheel in the correct position. I walked away from the accident, but the force of the diff coming across into the fuel tank under the seat, and my head deflecting the 1 inch 16 swg tube supporting the roll bar by over an inch had put a huge stress on my neck and the base of my spine. Five years after the accident I was in bed for a month unable to move (even to get up to go to the toilet for a couple of days), and it actually took my body ten years, and many trips to see the osteopath, to fully recover. On my first visit after managing to get out of bed, she said, “it is a shame you did not break your pelvis, as that would have relieved the stress”. She then went on to tell me exactly were the seat belts had been five years earlier, just from what she could feel!

So, if you ever have a heavy accident, even if nothing is broken, go and see an osteopath and get checked over.

It is interesting to point out that the roll bar was added to the top of the chassis, and did not go down to the floor. I’m sure that the damage to the base of my spine would not have been so serious if the roll bar had extended down to the floor.

That was the end of my racing, and as my daughter was born the following year there were not the funds to carry on. I should have just kept the car, but I sold it, and later on it was in the back of a van that was stolen – it was never seen again, which is sad after all the work that went into it.

Moving forward

There is a great deal that I like about Martin’s car, but mad as it sounds, I really want to make my own body. So my present thinking is to ask Martin to make me a slightly modified version of his chassis, which he is happy to do, and then get on with making the plug over the frame, for an all enveloping body.

Emlyn Coldicott

750 Painting .jpg
Original painting by Paul Dove
750 Painting .jpg (245.31 KiB) Viewed 4716 times
Last edited by EmlynC on Fri Mar 30, 2012 3:34 pm, edited 4 times in total.
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Re: Building and Racing the ESC 750 – 1981 & 1982

Postby pbove » Wed Feb 22, 2012 12:47 pm

Emlyn,

This was very interesting, thanks for posting it and good luck with your new build!

It would be an interesting exercise to get everyone to post the story of their first car or first season.

Peter
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Re: Building and Racing the ESC 750 – 1981 & 1982

Postby Martin Kemp » Wed Feb 22, 2012 8:51 pm

Thanks for a great article Emlyn.

The big change from your first career, as they call it in F1, is that there is a lot less trouble with the engine - or with Woodcote.
I think your suspension ended up similar to mine because Keith's parameters were very similar to my own.
It is the tyres that stick to the road - so give them the best possible working conditions.

With the aid of modern computing I can simulate variations in geometry in a couple on minutes including the effects of dive and roll. So much quicker than the old string computer.
On the other hand a balsa model is still a lot quicker than a finite element stress analysis and easier to interpret.

February Race Tech magazine has a very interesting about Jim Yardley's (former 750 constructor) latest designs. Not 750 cars but interesting for budding 750 constructors.

Martin
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