Well done chaps, progress
Well done chaps, progress
What's happening then, you all dead ?
Not at all Tony....struggling to find time to do updates, hopefully do one this evening. In short, we've been testing again last week and all went well, but we've also had to re-locate the car and kit to Ryan's place because I'm moving house. Not enough time in the day lately
That's ok then.
July 11th 2012:
If only we could get paid more and work less hours! Since the last trip up to Blyton Park, we have done a few modifications to the car and particularly the trailer. The trailer did reasonably well on it’s maiden voyage, but it did need a lick of paint. In hindsight, buying a trailer on the cheap seems to have been a little bit of false economy considering what we have spent on it to make sure it remains a solid trailer, but we can certainly say that we now all know just how a trailer works!
Our test was scheduled for July 11th and seeing as I would be moving from my current house at the end of July, our plan was for the car to go straight to Ryan’s place near Loughborough after the test. So, we had to pack keeping in mind that this would be the case. Below you can see how tight the trailer fitted in to my garage with the car on. You can also see that we have started apply some of the decals that will grace the car in the TinTops series.
After the last test we found that inside the c**kpit it was getting rather warm. So we decided to try and increase the air flow through to the driver by making a little home-made scoop on the driver’s window and cutting a few holes in the rear side windows.
We made our way up to Blyton Park for our trackday and unlike last time, we were bang on time!! We felt a lot better prepared second time out and even got ourselves a little gazebo to protect us from any sudden downpours which were bound to come our way.
We had sat down prior to the test to draw up a bit of a test plan for the day. We would start the morning doing short runs to get the tyres up to temperature and set our pressures. Then we would monitor the temperatures across the tyres with an eye for adjust camber at front and rear. I was enlisted as driver for the morning, whilst Ryan and Rob would do all the measuring and changing of pressures. Since the last test, we had decided to fit a rear anti-roll bar and on the first run out, it already felt a little more positive. However, the car was still understeering quite a bit and in certain corners it would hop around a little.
Around 11am, the most brutal short shower fell, completely soaking the track. We decided to continue running the car so that we would get a good feel for the changing track conditions. Unfortunately at this point, we managed not to record any footage of the car which was a shame as there were a few hair raising moments! The sun came back out within an hour of the rain first starting to fall and the track began to dry up. We had been smart enough to take the opportunity for us all to get out in the wet, so we all got a feel for the wet conditions.
As we approached the lunchtime break, it was decided that we needed to remove a rear camber shim, so that is what we did! After the break, with the sun shining once again, it was time for us all to rotate in the car and start to work out how to set our dampers up, which we still had not really properly explored. We made a few minor changes which seemed to move the car in the right direction but it was still not handling great. After more adjustment, we began to realise that the springs were too soft for the damping setting we had set it to and considering that we were nowhere near the stiffest damping setting, this was worrying. Near the end of the day we made a bigger step in the soft direction with the dampers and the hopping of the car began to dial itself out, confirming our suspicions. We have decided that we need to get some stiffer springs for the next time out in order to match the capability of the dampers we have.
Nonetheless, the afternoon was a success and the weather held out for us to do a lot of dry running. We all went in the car with each other, observing closely, ready for feedback post test. Ryan managed to post the fastest time of the day and the video should be viewable below…..
With all that’s been happening away from the project and the distinct lack of money we all seem to have, we have taken the decision to do one final test before entering a race. Some of us wanted to head straight in at the deep end and some of us wanted to take our time about it until we were really really confident with the car. So a compromise was reached and we all agreed it was the best thing to do.
The plan is to do another good value trackday in august and seeing as the car is now about 20 minutes from Mallory, it will make it’s way there to see the scrutineers. Then, all guns blazing heading to Donington in September. We are all really enjoying ourselves with the project, the development has been hard so far, but a real great learning experience for all of us.
This is Rob Chase of Chase racing. Iíve been trying to do some research and not come up with any answers on the internet. I was wondering if anyone can give us some advice on the following points.
We want some stiffer springs. We got a set of barely used Gaz gold coilovers which have apparently been valved for sprints and hill climbs but the springs seem very soft. Apparently the dampers are good for upto 900lb/in.
My quick sums for a ride frequency of 2Hz split +5% rear, -5% front give me 630lb/in front and 530 lb/in rear (assuming 1.4:1 rear motion ratio. 1:1 front). Does this sound reasonable?
Does anyone have any ideas on how to work out the roll gradient for a Clio or have a rough idea what the roll stiffness of the rear beam is?
Has anyone tried making their own wishbones? Iíd quite like some more caster and be able to adjust the camber without camber bolts.
Has anyone removed their front anti-roll bar? Recommended? If we do make our own wishbones it gives us the opportunity to make an adjustable front ARB which I think would be a lot more useful than an adjustable rear one.
Has anyone experimented with the power steering? I think that the steering is overly light (although the other two think Iím just winging) and struggled to feel any under-steer through the steering wheel. I took apart an old BMW PAS pump and figured that if the Clio one is anything similar then cutting down the flow control valve to remove some pre load should reduce the output pressure without affecting the flow rate too much. Iím assuming that changing the torsion bar is pretty much impossible.
Is it possible to get anything like this that will fit on a Clio ball joint?
If you are getting the heat into the rear tyre's (Especially the dunlops) then you will want to have the rear rate's nearly equal the front's. Are you taking into account the rear spring being inboard which alters the effective spring rate?
The ARB's are something that I am getting sorted in the next month or so and yes will be removing the stock front ARB to replace
Thanks for the advice Ash. I accounted for the spring being a bit further forward than the wheel centre with a motion ratio of 1.4. I havenít accounted for the geometry at the front largely because I havenít measured it yet. It should be a lot less significant though.
We are getting a reasonable amount of heat into the rear tyres. Fronts were stable at about 70C on the inside shoulder and rears were about 60C. It turned out that they were about 5PSI under the recommended hot pressures on the spec sheet (which we neglected to read until afterwards) after we set the pressure based off the temperatures so I expect a bit less hysteresis when we run them at a higher pressure. I have had a look at the steady state lateral weight transfer but again most of the numbers I used are estimates. Normally road cars have no more than 30% of their roll stiffness contributed by the ARBs in order to reduce head toss. Renault must have thrown that out of the window when they attached the rear wheels together with a girder and the rear roll stiffness must be massive. When I factor that (guess) in, the weight transfer via the sprung mass is almost entirely at the rear axle. Which should make it really oversteery. The understeer weíve got at the moment is really frustrating though and I was considering ditching the front ARB altogether. The difference in the spring rates that I had (except for that attributed to the different motion ratios) was to try and keep the front and rear in phase when they both run over the same bump in order to minimise pitching. However thatís not a real concern and Iíll have a look at having them more similar. I think the rear springs we have at the moment are a fair bit softer than the fronts so this could be the cause of our frustration. Do you mean that the front and rear natural frequencies should be closer which would be more normalised for the weight distribution or that the absolute stiffnessís should be similar?
You're getting decent heat into the tyres mate I'm afraid I'm not all that much of an expert I was just trying to share the couple of bit's I have learnt along the way. I have a lunch date with my suspension guru tomorrow although you would understand a lot more of what he says than I do lol !
Surely in order to ditch the front ARB you would then have to stiffen up the front end to compensate and that would then reduce grip, compliancy and traction?
Yes I had the same issue with the rear of mine and the springs were so soft, what shape springs do the Gaz coilover's run? With my new setup I think I am going to be running roughly the same spring rate front and rear although I am still retaining inboard rear spring location. I increased the rear spring rate by just less than 10% on my previous setup and it really helped get rid of some of the understeer.
Sorry I can't be of any more help Rob I'm not good with all these complex things so I have had to get someone to help me with it all! My thread will be updated with the progress I make with it all however I can't promise it will be a quick process!
Itís really useful information Ash. Anything we can learn from someone who has already tried things should stop us heading down dead end routes.
Iím hoping to do two things with the new springs. Increase the overall stiffness which will limit the steady state (constant acceleration (force)) pitch and roll. With appropriate damping that should make it change direction with much less lag. The other thing is improving the balance. Thatís largely done by altering the proportion of the resistance to roll that the suspension at each end gives.
I thought the rear beam would mean that the rear was much stiffer than the front in roll so wouldnít suffer from under steer too much. Adjusting the damping should allow us to adjust the front / rear stiffness in the transient (turn in) situations.
The best way to think about this I believe is a four legged stool with the front two legs being made of foam. You can put a lateral force on it and the front legs will maintain a similar force down on the floor to each other whilst only one of the rear legs will push down on the floor.
There are several things which influence a tyres behaviour but assuming all else is equal, the larger the normal (downwards) force, the larger the slip angle (angle between the rubber of the contact patch and the rim). Therefore with a stiffer rear end than front, the front wheels should have a similar normal force but the rear outside wheel will have a large normal force and therefore a large slip angle Ė oversteer. If youíve seen a bicycle model, asymmetrically loading the tyres should reduce the cornering stiffness (d slip angle / d lateral acceleration) of that axle.
It seems like the rear beam on its own wonít be stiff enough to do this as Iíd originally hoped so Iíll need stiff ride springs too. By getting rid of the front anti roll bar we would be having a significant effect on the relative front rear roll stiffness. but I'm a bit hesetant to do this witout knowing how stiff the rear beam actually is. Someone who I used to sit next to at work used to have a clio cup car which he had converted for rallying. At one point the chassis twisted a bit and the bushings in the rear beam carriers sinched up and the rear of the car became the anti roll bar. He ended up narrowly missing a tree which was what inspired us to put a cross brace in the back of our car. It shows that the rear beam must flex quite a bit when cornering though.
The Gaz setup we have is coil overs at the front and replacement springs and dampers in the original positions at the rear. Weíre not certain what the actual rates are but should have them off the car to measure pretty soon.
We fitted one of those kits over the winter, very good.
It's a lot of welding.
(dave here now) Yeh, we used that kit as a model for what we have done to our rear beam. That along with the cross brace in the back is hopefully helping us maintaining a decent amount of body stiffness, hence why we think we're being limited by the stiffness of the springs now.
Would this help? http://www.pure-motorsport.co.uk/details.php?itemid=120
We were advised against using both, as there will be no give in the rear at all.
One little bump, bang goes the shell.
The rear beam is surprisingly flexible however I will be able to give you exact figures in August when we work on it. I will try and remember more of the technical stuff he explains to me as i'm still baffled
With regards to removing the front ARB you obviously know what you are talking about on suspension and I'm the first to admit I'm only just starting to learn but surely by removing the ARB you are then going to be solely relying on each damper to maintain the degree of roll that you want to achieve with your setup. In order to do this surely you will have to have each damper/spring so hard that they are then ineffective at what they are trying to do which is control the damping to allow traction, grip etc? Sorry if I am wrong (probably am) but just trying to learn what controls/affects what
August 2nd 2012:
All change please, all change. As you may have read from the last update, I (Dave) have had to vacate my previous property where the car was being kept. The original plan was to keep the car at Ryanís place, but I had an offer from a colleague at work to hire out his garage (very close to my now old house). So, we decided to take him up on the offer!
The new setup (seen above) is a 3 birth garage which we affectively have two-thirds of. We will still share the usage of the garage, but it is predominantly for us to work on the car. We can keep the trailer outside as well, as there is a gate locking it inside a small courtyard area. The garage also has the most useful pit too, itís great! First impressions are very good, the usability of the place is even better than we had at my previous property and we even get cups of tea!! Although it will cost us, above the zero cost for Ryanís garage, it will be far more convenient for us here and in terms of overall travel time, it will prove to be a fair bit less between us.
The garage and pit have already proved their worth, as we began some more work on the car. The task for the evening was to the remove the subframe along with the steering rack to carry out a few other jobs. We had a starter motor problem that needed diagnosing and our assumption was that it needed replacing, so access to this would also be essential.
We were very pleased with how the increased access helped us get to all the necessary fixings and the subframe was soon free. After being able to get to the starter motor, we can see that the feed to the solenoid has come offÖ.so we are very much hoping that this is the reason we had a problem. We wonít find out until the subframe goes back in though, because we donít want to start the engine whilst itís not fully supported. Fingerís crossed that has saved us another job.
Next on the agenda is to refresh the steering rack by replacing the rod ends and get a good solid mounting for the rack on to the subframe. We will then change the wishbone mounting position for a more suitable wishbone angle. A couple more small jobs on top of this and the car will be ready again for another test on August 31st down at Castle Combe. More to follow soon!
Take the plugs out and spin it over quickly, just in case you have to take it all out again.
Nice pit btw, they are very useful.