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Author Topic: Bagheera Roll Cage wanted  (Read 69702 times)
Anders Dinsen
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« Reply #90 on: August 03, 2009, 09:21:22 am »

What a lot I don't know!

Haha - well we can all say that! Learning is great Smiley

/Anders
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andyowl
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« Reply #91 on: August 05, 2009, 08:25:55 am »

Suspension test drive last night...

The improvd links on the rear ARB seem to have made a big difference to how the rear of the car feels. Much tighter with a more controlled feel. This is the first time I have driven the car on the public road (other than going to the annual test) and it is hard to make objective comparisons but I am pleased with the result for a very modest cost.

I adjusted the front suspension by two turns of the torsion bolts after slackening the shaft that holds the rubber bushes on the upper wishbones. There was a slight reduction in the ride height before the test drive and a bit more afterwards. It has gone down about 10-15mm but is still higher than our Grey Baggy. More adjustment needed.

The rear suspension had also been adjusted but when I measured the ride height again before I went out it was 3mm HIGHER than before. I realised that I had taken everythng out of the luggage compartment (including the supercharger, 2" SU carburettor and most of the air cleaner system!) and that made the difference! After the test drive I measured the ride height again and there was no reduction. More work needed. I have ordered the two 45degree angled M6 grease nipples and they should be here next Monday. The Matra German instructions recommend the use of Molybdenam Disulphide (MoS2) as the grease but I am wondering if PlusGas or similar release oil will be better initially. I also wonderd if it might be better to blow release oil into the new drillings using 7bar compressed air rather than a grease gun filled with liquid oil. I have also thought about making a clamp to force the trailing arm towards the steel adjustment cam and then hitting it hard! "If in trouble or in doubt, get a bigger hammer out" (Marine Engineer's Golden Rule - it often works).

The good news is that the new 25mm wheel spacers do not seem to be causing a problem with the tyres hitting the GRP wheel arches. Even driving fast over speed humps did not cause contact. This may change of course when I eventually get the suspension lower but it is a good start.

Back to the garage...

Andy
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andyowl
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« Reply #92 on: August 08, 2009, 10:10:09 am »

Suspension update, Saturday August 8th.

Well I've fitted the grease nipples to the RH rear suspension after failing to get it to move more than 2.5mm (reduction in the gap under the adjustment cam) using brute force and hammers.
 
Looking at the sectioned trailing arm I am not too hopeful that any grease will get though. The clearance is so small and what was there is filled with ally/steel products of corrosion. I tried to get some PlusGas into the grease nipple but it came out of the side! Wait and see I suppose.
 
I made a heavy duty clamp using two 12mm x 40mm steel bars with M20 studding at each end in an attempt to compress the adjustment cam and reduce the gap. In the end I bent the bars! Even using a "sledge" hammer, in a confined space admittedly, it still didn't shift.
 
Even though I have reduced the clearance under the adjustment cam (I had already opened it by nearly 3 turns on the screw to give a gap of 5.8mm) to 2.6mm the change in ride height is negligible. It is still higher than Grey Baggy! I calculate there is a 1:4 ratio, gap change to ride height change, so I should be looking at a height change of around (5.8-2.6) x 4 = 3.2 x 4 = 12.8mm and that should be measurable even visible!. So I have decided that I will abandon the rear suspension changes until after the Etretat / Le Havre Hill Climb in two weeks time.
 
"Plan B", if waiting for a while doesn't work, is to remove the arm and make a single slit at the forward ends of the casting to try and relieve the clamping forces of the casting around the steel shaft. I am thinking of using a large "U" bolt or two on each leg of the arm to augment the ally strength afterwards although my instinct is that it will not be necessary. Desperate I know but I really do need to lower the rear suspension!
 
To my surprise the front adjusters have not been a problem. They must have been greased at some time. I have not yet worked out the ratio of adjustment to height change. At the moment there is about 30mm of thread available to adjust.
 
I have started to measure "Ride Height" an easier way. I just want it as low as I can without tyre rubbing or grounding on the speed humps in our road! For comparison purposes I have been measuring the distance from the underside of the wheel arch to the ground on the centreline of the wheel. Saves all that stooping or crawling underneath. I would be very interested to know these dimensions on your Bagheeras!
 
I checked our standings in the AutoSolo championship that my motor club (FDMC) are running. There are 10 cars in the Historic Class, 9 of them Healeys or MGBs and one Matra. The Matra is 5th out of 10! How about that?
 
Andy
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andyowl
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« Reply #93 on: August 12, 2009, 10:03:56 am »

Tyres and pressures...
I just sent this email to Yokohama UK about the pressures they recommend for the A048 tyres I am using. I await a reply.

Dear Simon Clark,

I would very much appreciate your comments and advice on the following set-up.

I am using A048 tyres for MSA National B Sprints and Hillclimbs plus clubman AutoSolos on a 1977 Matra-Simca Bagheera S. This is my first season.

Tyres are run cold or luke-warm, at best, after several runs. See below for further details.

Total weight on the start-line is 1,045kg with a 45/55% front/rear weight distribution i.e.:
- total front 470kg and rear 575kg
- or per tyre front 235kg and rear 288kg.

Tyre sizes are: F: 185/60 R13 80H
                        R: 205/60 R13 86H
based on the tyre width and circumference I have used on another road-going Bagheera for >15 years.

Wheels are 5 1/2" J original Bagheera alloys now with wheel spacers of the maximum MSA will allow i.e. 25mm.

The car is mid-engined 1,442cc with around 85BHP driving the rear wheels. Lefthand drive with full 5 point roll cage.

Could you recommend tyres starting pressures for further experimentation? I presently use 27psig (1.86barg) front and 30 (2.07barg) psig rear. I started with much lower pressures (copying the pressures used on an Alpine-Renault with A048 tyres) but the car handling was very poor. These pressures are around 2psi (0.14bar) higher than those used on the road-going Bagheera with similar width Pirelli tyres.

Understeer has been a problem but using better anti-roll bar mountings (harder bushes and Rose joints on the linkages with "slop" drastically reduced seems to be improving that. Stiffening the ARB itself has not yet been tried due to lack of suppliers.

Tyre temperatures were measured at the Longcross Chertsey Sprint last month after each run (infra-red non-contact meter).
- Ambient temp was around 72F/22.2C  (I forgot to measure it - sorry). I forgot also to measure the road surface temperature. Weather was cloudy but dry.
- I was interested in the temperature variation across the width of each tyre as well as the average tyre temp front and rear.
- Temps are measured in Fahrenheit & differences in Rankin degrees as this gives 50% better resolution with a single decimal point display.
- Maximum temperature seen (after the second practice run) was 102.4F/39.1C (left rear inner - closest to the exhaust?) with the coldest 87.8F (right front centre).
- After the 2nd competitive run (it rained briefly before the start of that run and the track was slightly damp):
     - the difference across the width of each tyre was: left front = 1.8R, right front = 0.6R, left rear = 2.8R, right rear 1.6R
     - the average temp on each tyre was:    left front = 96.5F, right front = 95.6F, left rear = 92.4F, right rear = 92.0F (This is also the order in which I took the readings. Maybe there is some "cooling down" trend here??)
- I regret that I did not check the tyre pressures again at the end of this run nor check the temps or pressures after the 3rd run.
- I have all the above on an Excel spread sheet if that would help.

Hoping for your help. The tyres are fantastic and everything I was lead to believe. I will certainly buy them again for next year, unless you have something more suitable for my needs!

Thanks in advance,

Andy Owler
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JL
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« Reply #94 on: August 12, 2009, 04:33:52 pm »

Andy
If it any help I used to run 28psi front and 36psi rear on my Simca Abarth race car when using Yokohama 008's.
Regards
John
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Anders Dinsen
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« Reply #95 on: August 12, 2009, 07:51:29 pm »

It will be interesting to hear what they have to say!
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andyowl
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« Reply #96 on: August 12, 2009, 08:46:26 pm »

Andy
John wrote...
If it any help I used to run 28psi front and 36psi rear on my Simca Abarth race car when using Yokohama 008's.
Regards
John

Interesting that Yokahama 008s are "List 1a" at the moment. How did you find them in the dry and wet? The FDMC AutoSolo organisers are talking of banning List 1b tyres as they give an unfiar advantage to the users and are not really "entry-level" as AutoSolos are supposed to be. I was thinking about getting a set of 1a tyres to use "everyday",  and for AutoSolos, but it would be nice if they could be semi-sticky.

PS I received an "out of Office" message from the chap at Yokohama  so I do not expect an answer until next week.

Thanks,
Andy
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JL
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« Reply #97 on: August 12, 2009, 10:47:51 pm »

Hi Andy
Sorry, I should have said 008R, they were brilliant in the dry but poor in the wet; they were the same tread pattern but softer rubber. Some of the guys used normal 008 rubber and they were also pretty good in the dry. In the wet I used to use a soft rubber version of the Avon Turbospeed, they clung on for grim death but on the Le Mans Bugatti circuit I used 4mm of tread in 10 laps!
You could really do with having 2 sets of wheels and tyres. For the dry use a pretty well worn set of tyres - more stable with less tread movement and for the wet plenty of tread to move the water.
Regards
John
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andyowl
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« Reply #98 on: August 17, 2009, 07:44:27 pm »

Yokohama replies ref tyre recommendations....

Hello Andy,
                        Thanks for the info.
 
                        It looks like that you have a fairly even temperature spread across the tyre treads. However taking temperatures on a treaded tyre can sometimes be miss leading. If possible try to use a needle probe type pyrometer so that you can take the temps. at the carcass, this gives you more consistent readings, as the heat tends to radiate away at varying rates from the tread surface. A temperature spread with  a variance of 15 to 20 degrees C across the tread is quite acceptable.
 
                        You could try lowering the cold starting pressures by 4 -6 psi, as the hot pressure needs to be around 25 - 28 psi. This of course will be dependant on weather and track conditions etc. Also try using the same pressures for the front and rear, this should give you a more neutral handling balance.
 
Best Regards
 
Simon
....Ends

Interesting suggestions!
- I am surprised that a temperature variation of 20-30 degrees C  is acceptable!
- I will try to take temperatures in the tyre grooves - I was trying to avoid them before!
- Lower tyre pressures to start with are also worth trying (1bar=14.5psi)
- Equalising pressures front-rear is also something I would not have tried as I was following the Matra design.
I'll give them a try at Etretat this coming weekend.

Andy
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JL
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« Reply #99 on: August 17, 2009, 10:49:46 pm »

Hi Andy
I will be very interested to see your feedback from Etretat armed with this latest information; the concern I would have is getting the tyres up to temperature quickly enough but it has to be worth a try.
Good Luck for the weekend
John
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andyowl
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« Reply #100 on: August 26, 2009, 09:22:34 am »

Etretat was not what I hoped for!

Driving back to the paddock from scrutineering in the town centre, there was a very loud "bang" and the feeling of running over something large and hard. A grinding noise also started and I stopped as quickly as I could.

There was nothing on the road behind me and I looked underneath expecting to find something trapped there. But nothing!

I set off again and the grinding started again in time with the road wheels and rythmic. Another look still showed nothing, not even oil leaking. To make a long story shorter the differential casing had broken into several pieces but this was only seen after I had driven about 10km back to the paddock via a Bricolage in a neighbouring town because I and several others needed large hose clips to secure better the fire extinguishers as demanded by the scrutineer. A Simca 1100Tii driver lifted up Baggy Joe and we could see the gears inside the differential rotating. My weekend was finished!

Back home I have started to remove the differential. The whole of the right side of the casing is separated from the left side with some additional large casing pieces loose but still supported by the gear shift rods. I cannot imagine what force was needed to break the aluminium casing which is 5-8mm thick where some of the breaks are located. Photos will follow!

Some possible clues...
- I had seen a few drips of oil after the last Sprint three weeks ago but failed to investigate it properly. Maybe the casing was starting to crack? I assumed that an oil seal was leaking but obviously not seriously.
- I had "Check the diff and gearbox oil level" on my list of things to do. But I forgot.
- That morning I had bumped up a grass "kerb" on the exit road from the paddock. Could this have stressed the bottom of the casing?
- The previous day I and my wife Charlie had been in Baggy Joe to the same Bricolage for a water pipe for the motorhome with no problems. The diff was obviously not at breaking point then.
- I have "only" owned the car for 14 years. What has happend to it in the previous 18 years? Who knows?
- I should count myself lucky that it has done so well thus far!

What now?  An AutoSolo in 3 weeks and a Sprint on October 11th. Both entered and paid for. Both are end-of-season events too.

Well I have several spare diffs in the store. One is complete with a gearbox and bell housing but its condition, like all the others I have, is unknown. But at least I know the gearbox output matches the diff input. Another diff and gearbox are lying together so they are probably a pair. Maybe the others might donate a casing so that I can rebuild the old one (if the gear teeth are not too bad!)

My "wish list" would include a Rancho Grand Raid Limited Slip differential and gearbox. Does anyone know of one for sale? I would also like Rancho low compression pistons for the supercharger engine to be fitted during the winter. Any ideas? I will put messages onto the forum, search the net and ask the expert Rancho people I know. Any other help will be most welcome!

If any Francophone Forum Members would place french messages on the Rancho websites I would be most gratefull. I would not want to destroy a Grand Raid but someone may have taken one to pieces in the past.

In the meantime... back to the garage.

Andy
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Anders Dinsen
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« Reply #101 on: August 26, 2009, 07:16:20 pm »

What a pity! It should have happened during the race, that would have been much more fun!  Cheesy

There must have been a small crack somewhere in the diff casing, and the torque has just ripped it apart. After all, aluminum does corrode...

I hope you'll be able to find a limited slip diff. It will be interesting to hear about your experience with it. Don't forget, however, that a limited slip diff will consume power and since you are track racing (and not rallying), you migt be able to achieve the same effect without power consumption by working on the suspension (lowering the ride height). But this is just speculation, of course. Only if you try it will you know!

I get the feeling that you are not too put down by this incident.  Keep up the good work! Smiley

/Anders
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andyowl
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« Reply #102 on: August 27, 2009, 12:20:06 am »

As you suspect I am not too put down!

In truth I am pleased that it did break on the road and not on the Hill Climb. Most of the Etretat course is edged by Armco railings and a broken diff during hard acceleration around one of the corners would have probably spun me into the railings with considerable damage to the car if not to myself.

I have never heard of a Bagheera diff breaking before so I hope this is a freak accident. Fitting another one and taking more care with oil checking is all I can do at this stage.

The good news is that a new Historic Class Hill Climb Record was set by Gerard Magro in his CG-Simca!

Andy
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Anders Dinsen
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« Reply #103 on: August 27, 2009, 07:36:45 pm »

In truth I am pleased that it did break on the road and not on the Hill Climb. Most of the Etretat course is edged by Armco railings and a broken diff during hard acceleration around one of the corners would have probably spun me into the railings with considerable damage to the car if not to myself.

Ah, very good point. The armco is safe for the spectators, but must be a horror to drive between!  Shocked

/Anders
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JL
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« Reply #104 on: August 27, 2009, 10:35:28 pm »

Hi Andy

If you go for a LSD you really need a unit that you can adjust; I am not sure but I think that the Rancho unit is a full locker so that if one wheel starts to slip a small amount then the diff locks solid. In the wet that will give you serious understeer, in the dry if there is a lack of power to break traction on both wheels you will also get more understeer but when you have sufficient power to break traction you will go very quickly from understeer to oversteer!
If you have an adjustable diff you can allow more wheelspin which will reduce understeer but not give you a wild transition to oversteer.
If you are really set on a LSD, install it before you do much work on the suspension.

Regards
John
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