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Author Topic: Bagheera Roll Cage wanted  (Read 67608 times)
Spyros
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« Reply #60 on: July 11, 2009, 11:11:51 am »

Nice to see the evolution.
What kind of paint did you use ?
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andyowl
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« Reply #61 on: July 14, 2009, 09:12:28 am »

The paint used was purchased from a supplier I found on the internet. They are in Altrincham, Cheshire and supply by mail order. Contact Geoff Morton, 07740 103894 or 0161 969 3980. He races classic sports cars (mainly British) and is very efficient. When I looked like running out of top coat before I had finished the job he supplied another 2.5 litres of mixed colour within 24hrs of my order delivered by courier, by 0930 next day. Impressive!

The paint manufacturer is Palinal (Palinal Vernici) from Brescia, Italy (mail@palini.com).  The paint type on the tin was "Nitro Airdry" and on the technical data sheet as "NitroSynthetic Enamel Class 407". I understand this is a fancy, technical, name for "Cellulose" i.e. the traditional paint as used by Matra originally.

It is VERY FLAMMABLE and you must NOT have anything electrical switched on when the paint and thinners are in the air. Spraying in the dark is not easy and I compromised by having the garage doors 25% open and both windows at the rear of the garage also fully open. It would have been good to have a "bug screen" over the window apertures to keep leaves and flies out but in practice this proved not to be a severe problem. I hung PVC thin plastic dust sheets over the walls and doors to minimise the paint dust settling everywhere and that seems to have worked quite well. I chose a windy day for the spraying to help disperse the fumes quickly. I hung a piece of this plastic sheet below the "up and over door" so that I could see by its movement that there was plenty of air flow through the garage.

I moved the compressor out of the garage into the adjoining "bike shed" to take it away from the flammable gases. I left the ceiling fluorescent lights on all the time and turned everything else off especially our gas fired central heating boilers which are also in the garage!

Personal Protective Equipment : 
Breathing: I used a breathing respirator from www.RSWWW.com  part number 228-7934. Manufacturer is JSP Ltd., Oxford and model Olympus "Filter-Jet" to EN405:1992.  It is specifically intended for hydrocarbon (organic) solvent vapours and particles and I was impressed with how well it worked! On the first day I forgot to put it on and half way through I began to feel a bit dizzy. Someone had warned me of the dangers of breathing the fumes so I stood beside the open window until the fumes, and my head, cleared. Afterwards I used it all the time and did not notice any bad effects. I only noticed how good it was when I had finished spraying and took the mask off. The smell of thinners hit me like a train! Recommended!

Gloves: Thinners and paint dry the moisture and natural greases out of your skin very quickly. I used protective gloves from RS (part 186-3509) by Ansell Edmont. Sol-Vex in Belgium. Quite thin with a cloth type lining I found them very good. My hands always sweat wearing these type of gloves but that discomfort is small compared with the pain of sore and cracked skin! Also recommended.

Cover-alls. I used a disposable "boiler suit" which stayed remarkably clean. RS 405-492 is the part number. It has a hood with a drawstring to protect your head and the garment was about 1.5 sizes too big! A belt would have been good to stop the slack around my waist touching the car (I can't often say there is slack around my waist these days!)

Eye protection: Wearing glasses I tend to ignore eye protection but this time I wore a simple face mask, mainly to stop getting paint on my specs!

By the time I had got all this gear on I was both hot and steamy but well protected.

Since the above information is "safety related" I take it seriously but I need to say that if you choose to copy what I did then the financial limit to my liability is the same as the amount you paid for the information i.e. zero!

Andy

PS Pictures of the finished result at the FDMC Summer AutoSolo on Sunday.  Pictures going off to France today with my entry in the Etretat Hill Climb in August!
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andyowl
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« Reply #62 on: July 16, 2009, 09:35:52 am »

Baggy Joe's entry for Etretat has been provisionally accepted. I was told that he would be the FIRST Matra Bagheera to compete in the Etretat Hill Climb! Last year's event was won by a Matra Djet with a 2litre BMW engine!

I have also learned that we came 3rd in the Historics Class at last Sunday's AutoSolo beating three MGBGTs (two with V8 engines). The winner was an Austin Healey Sprite with an MGBV8 in second place. There is hope yet!

Someone took a video of some competitors and it is on Youtube : http://www.youtube.com/watch?v=U2LneZS_dPc

Baggy Joe is at around 1m45s in the video.

The car seems to be rolling far too much! The rear wheel is almost off the ground!
- So what do I do to reduce the rolling? Suggestions very welcome!
- He also seems to have too much ground clearence and I plan to do some measuring today.
- He has new shock absorbers at the front but I stopped looking for new rear shockers.
- Going fast around corners also produced excessive understeer with the outside front wheel scrubbing off the speed very quickly. Not enough instant power to kick the tail out. Maybe more pressure in the front tyres?
- I have found a source of 25mm wheel spacers. They might improve the stability as well as look better!
- Introduce some negative camber on the front wheels??

Good ideas very welcome. Now well out of my depth!

Andy
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JV
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« Reply #63 on: July 16, 2009, 11:01:07 am »

Indeed, looking to the video my first reaction was: too much ground clearance and rolling too much. If you can reduce these you must be able to improve the performance substantially.

Jan
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Jan Verdam
Anders Dinsen
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« Reply #64 on: July 16, 2009, 04:41:11 pm »

The lack of underside body panels and the compressed 16:9 format into 4:3 of the video make Baggy Joe look a little like a racing 2CV Cheesy

A big congratulations on coming 3rd! That's very well done, Andy.

About roll: The only way to reduce roll is to lower the car (reducing the forces acting on the suspension), and/or to stiffen the suspension. Unless you go to extremes and change the suspension layout completely, but I guess that's out of the question...

But the fact that you go so well through the corners (despite the roll!) indicate to me that your car is performing quite well. How did it perform compared to the Miata's for example? It's quite obvious that you have a very good feeling of what you are doing, whereas the Miata drivers are either inexperienced or have less driver feedback from their cars - or both?

About understeer: Yes grip generally increases with increased tyre pressure (until a certain point) but the best way to set tyre pressure is to take a temperature measurement across the tyre surface. It should be even. This can be done with an IR thermometer. High temperature in the middle indicates too high tyre pressure (tyre bulging out), higher temperature on the edges indicate the reverse.

Increased camber can help, but the IR thermometer will help you there too: High temperature on the outside edge of the tyre and you should increase (negative) camber. And vice versa.

But there's one more way to reduce understeer, and that is to transfer load to the front of the car. Ballast is one way to do it, but it adds weight. Reducing rear weight is another, but could become expensive.

No, the way race car engineers have for years balanced their cars is by setting up the anti roll bars: Making the rear end stiffer, transfers load to the front wheels and reduces understeer. Make the front end stiffer, and you reduce possible oversteer. Etc.

This works by transferring load from the least loaded wheel, through the chassis, to the diagonally positioned wheel in the other side. So if your left hand rear wheel is very lightly loaded in a tight left hand corner, a stiffer anti roll bar will aid transferring load to the right hand front wheel through the spring/shock absorber and the cahssis. THIS will reduce understeer.

I think you may find inspiration on how to make an adjustable roll bar on this photo of a Matra F1 car. The roll bar is the silver bar starting next to the rear wheel in the front. The bracket on the bar is attached to a rod connected to the lower A-arm on the suspension. The bracket can slide front to rear of the roll bar to tune it:



New rear shocks should also be considered, as in the dynamic environment, they will also be transferring a lot of load from your cars' rear to the front.

The above is just theory, I'm not a race car engineer (I would have loved to be though!), but I've studied the subject for fun, and I've promised my second-oldest son that we will buy ourselves a Formula Ford to do some classic racing in - and to be successful in such a beast will require a lot of suspension tuning (while engines aren't allowed to be changed).

It's great to see you emerge from "your depth"!

Cheers,
Anders
« Last Edit: July 16, 2009, 04:45:09 pm by Anders Dinsen » Logged

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Spyros
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« Reply #65 on: July 16, 2009, 10:34:42 pm »

You can also try to playa bit with standard parts.
There was 2 thickness of rear antiroll bar.
I also know that the 2 little veritcal links can have a lot of impact. If the rubber parts are not good ...
And the dampers.
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JL
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« Reply #66 on: July 16, 2009, 10:47:59 pm »

Hi Andy

For a little light reading get a copy of this book.

http://www.amazon.co.uk/Race-Rally-Car-Source-Book/dp/0854295720/ref=sr_1_2?ie=UTF8&s=books&qid=1247776957&sr=8-2

There is also a later edition of the book on Amazon but I have only read the earlier one.

Good Luck
John

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andyowl
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« Reply #67 on: July 17, 2009, 05:18:55 pm »

What a lot of advice! Thanks very much.

- I have ordered the Amazon book.
- I'll check the rear ARB bushes. Would stiffer bushes help??
- Bagheera spares book gives Rear ARB thicknesses as 18 or 19mm (section K44). I have no idea what I have now. Will check while I'm underneath.
- Rear Shockers seemed to operate smoothly and progressively just exercising them off the car when we were restoring him.
- I checked the ride height last night and it is significantly higher than grey Baggy. I'll report back to you the numbers shortly.
- How do you calculate the correct tyre pressure? Ask Yokohama perhaps? I know the overall car weight (945kg)and I think the Bagheera distribution is 45% front, 55% rear.
- I have an IR thermometer - I'll give it a try. One complication is that the short races may not allow the tyres to heat up enough to detect the changes. Running fast on a Motorway may give the same answers? I'll try it at the "Sprint" on Sunday.

What a lot to try!
 Thanks again,

Andy Owler

PS My Etretat entry has been confirmed today. International motorsport! Wow! Watch out next for WRC entries!

AMO
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Anders Dinsen
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« Reply #68 on: July 17, 2009, 07:20:56 pm »

- How do you calculate the correct tyre pressure? Ask Yokohama perhaps? I know the overall car weight (945kg)and I think the Bagheera distribution is 45% front, 55% rear.

I don't think there is a formula for it - experiments is probably the best solution. If you can find a deserted parking lot and set up some cones in a circle making a skid pan, you can try different setups and see how fast you can do corners with them. It doesn't only come down to weight distribution, but also camber, suspension, load transfer... It's a difficult science!

Quote
- I have an IR thermometer - I'll give it a try. One complication is that the short races may not allow the tyres to heat up enough to detect the changes. Running fast on a Motorway may give the same answers? I'll try it at the "Sprint" on Sunday.

In that case I'm afraid you could look at tyre wear. Your sticky tyres should wear pretty quickly, so you might be able to even detect wear after a few laps or so...

Since the motorway is mostly straight, I wouldn't count on it... a long drive on country roads is probably better.

Quote
What a lot to try!

It will never end! Cheesy

Quote
PS My Etretat entry has been confirmed today. International motorsport! Wow! Watch out next for WRC entries!

Haha, we will look out for you in WRC - you can count on it! You might consider a partnership with Prodrive - I think they have a WRC team to spare after Subaru shut down...

/Anders
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JL
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« Reply #69 on: July 19, 2009, 11:50:45 am »


Hi Andy

I would suggest your first port of call is to get the car lower and get a set of decent adjustable shock absorbers and set at mid range, if you cut down the rear coils this gives you a stiffer spring rate – not such a bad thing. Once you have done this, either go on a track day, a sprint on a decent length track or a practice session at a local circuit - most used to do this for half a day midweek.

 Run the car with near standard tyre pressures and then check your tyre temperatures across the width of the tread and note the readings, then adjust the pressures in small increments up or down and then recheck the temperatures and continue to compile your data(remember hot and cold readings will be different). You will then be able to see a pattern develop and you should also feel the difference in the car, you must  drive quickly but  be consistent and smooth and not drive wildly(watch Jenson Button - smooth but quick) and try achieve the best compromise for an even temperature across the tyres.

You can then try adjusting the dampers up and down making adjustments to the front and rear independently; again you should be able to feel the difference in the ride and handling and keep checking the tyre temperature.

The last port of call for you probably is the spring and roll bar rates, on the circuits which are generally very smooth I ran my cars very stiff – particularly at the rear, 1000lb springs in the rear of a Simca Abarth Corsa (based on Simca 1000 and rear engined) but for sprinting and hill climbing I would tend not to go too stiff but play with the anti roll bars.

Unfortunately this is all very long and drawn out but unless you can find someone who has done it already and then convince them to divulge the results it is the only way.

Hope this helps a bit.

Regards
John

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lewisman
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« Reply #70 on: July 19, 2009, 11:04:58 pm »

All good advice, but Baggys have torsion bars at both ends so spring rates are adjustable by tensioning torsion bars which if I remember right means that increasing the "spring rate" increases the ride height.

Also, if my memory serves me well, the rear adjusters on a Baghhera seize up on the drive from the factory to the showroom!

Body roll might not be the main problem. First generation Renault 5s had plenty of roll but when they hit the stops they still made it round corners. 

I would try to find out if you have a genuine understeer problem first. You may need a lower tyre pressure at the front than you might expect due to the light front end and weight transfer.  You are not going to powerslide a Bagheera on a dry circuit so oversteer is unlikely!!
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JL
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« Reply #71 on: July 20, 2009, 11:17:42 am »

Hi Lewisman

You are right of course, I had forgotten that the Bagheera suspension is different to the Murena, the years have dulled my memory. It would really help to get the car lower but I now remember on my wife's old Bagheera the rear suspension was seized solid and changing the clutch mas an absolute mission!

I think concentrate on tyre pressures and anti roll bars first.

One trick we used to use when spring rates needed upping and we were restricted on spring modification was to modify the shock absorber top mount to make the upper mounting washer removable and then slip rubber bump stops over the shaft to act as additional springs thus upping the rate, all good fun but maybe over the top in this case.

Regards
John
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Spyros
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« Reply #72 on: July 20, 2009, 03:23:03 pm »

My yellow Serie 1 S had during a long time a lower than normal ride height.

I change it to normal but the capabilities of the car was also altered.
I agree with John, get it closer to the ground.
Some says that they are able to unseize the rear arms by heating them
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andyowl
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« Reply #73 on: July 21, 2009, 09:46:54 am »

Well thank you all for the advice. What a team!

An update while I produce all the testing figures in a digestible form. I have ride height data and tyre temperature data to present but I need to collate it first.

In the meantime we have tested the front suspension ride height adjusters (torsion bar screws) and they work OK. I have not yet tried the rear adjusters, but one has been fitted with a grease nipple by someone in the past. By whom and why I have no idea. And why only one side??

Front ARB bushes are new in the last 6 months. The rears are worn but not too bad. Surely replacing these bushes with "Rose Joints" would make for better control and less "slop". Would not this be beneficial and relatively simple to do?

The "Scorpion" Sprint on Sunday at Longcross, near Chertsey was good fun on a 2mile / 3.2km former army vehicle test track. A fast banked section, a long straight, the "Snake" being a series of 90deg, 180deg bends and chicanes with another adverse camber 90deg bend and long lefthander to finish. I came close to the bottom of the results table but it was a "National" event not a club affair as the previous Sunday. I took 4 sets of tyre temperature readings which are interesting and worth analysing.

What Scorpion showed, as if I needed reminding, was that Baggys go round corners very well but lack power for the straights and long curves.

Last night I convinced myself that fitting the smaller Shorrock Supercharger (Blower) should not be too difficult. (Dream On!) I may get it out later and see if it can be made to fit! Fitting it to the existing 1442cc engine rather than putting the 1.6 Murena engine in at this stage will save a lot of time.

New pics to follow later.

Andy Owler
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andyowl
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« Reply #74 on: July 21, 2009, 10:33:00 am »

Some pictures of the "completed" Baggy Joe, last Sunday.

The raised headlights were not intentional! I have not yet connected up the vacuum system and when I was doing over 115 km/h they came up by themselves! I like to think of them as air-brakes, like an aircraft. This would account for my slow top speed and my lowly position in the results.

Andy
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