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Had a day off work so spent a bit of time on my build by visiting a roll cage manufacturer to discuss a cage for my car.
The design engineer in me found it very interesting as I got to see a few modern (Nissan GTR and Impreza Turbo saloon) bare body shells and the different ways in which manufacturers are now designing in stiffness, strength and crash protection. I know nothing about steel strutures and could see some neat ideas only let down by too many brackets on brackets.
Also had a look around a few interesting projects being worked on, 2 Paris to Peking classic rally cars, a Ford Model Y and a BMW 2002. A sports coupe being prepared for a big hill climb event.
I design with composites and have only designed one steel roll cage which was for the 1996 and 1997 McLaren F1 GTR that raced in GT1 and Le Man 24hrs. We finished 3rd behind 2 Porsches in 96 but smashed Porsche with a GT1 win in 97.
Back then we were doing some quite edgy stuff to get weight out but all the loopholes we used back then seem to have no been closed down by the FIA which in my mind is only a good thing.
We discussed how I wanted my roll cage and they have no problem making a RUF IRC style front section combined with a more conventional FIA rear section. I have also decided to fit low door bars for extra side protection. Only stumbling point was the price but I'm going to explore a few more options which will hopefully lower it a bit to something I can afford.
Stripping the shell to bare metal should compensate for the weight of the approx. 40kg cage which will be made using high strength T45 steel. Using T45 will keep the 40mm diameter tube wall thicknesses between 2mm to 1mm depending on the leads in each tube.
This short read may interest you in sourcing T45 in the UK if you decide to go with T45, as apposed to some of the more conventional chro-molly options.
This short read may interest you in sourcing T45 in the UK if you decide to go with T45, as apposed to some of the more conventional chro-molly options.
Captain,
I believe custom cages is based in the UK. They have T45 cages already prebuilt. I've done a handful of them. (not in porsche's but rally cars). All I can say is yes, their super light but take time to fit well. Especially if you plan on TIG welding them. They all come with "papers" to pass homoligation rules too.
You also need special benders to bend the stuff cause the wall thicknesses are so thin.
I usually make my own. Mostly in DOM. Most race organizations frown upon chro-molly...probably because most shops "cook" the chro-molly where the tubes fracture at the weld. A handful of people have been speared by the door bars....
Here's some of mine. https://www.flickr.com/photos/conwayautoworkscom/page3/
Kenny
Captain,
I believe custom cages is based in the UK. They have T45 cages already prebuilt. I've done a handful of them. (not in porsche's but rally cars). All I can say is yes, their super light but take time to fit well. Especially if you plan on TIG welding them. They all come with "papers" to pass homoligation rules too.
You also need special benders to bend the stuff cause the wall thicknesses are so thin.
I usually make my own. Mostly in DOM. Most race organizations frown upon chro-molly...probably because most shops "cook" the chro-molly where the tubes fracture at the weld. A handful of people have been speared by the door bars....
Here's some of mine. https://www.flickr.com/photos/conwayautoworkscom/page3/
Kenny
Hi Kenny, Custom Cages are the company I visited, very helpful abd their quality is top notch but as I want something that wasn't off the shelf the price was a bit too high for me..
I'm building a road car, if it was a race car I would 100% buy an off the shelf T45 FIA spec. cage from them.
My plan is to do all the time consuming fitting and just tack weld and then to be safe I will get a professional motorsport fabricator to TIG weld it all up.
a repeat post I know but thought it best to keep all my build stuff to this thread
Laser/water jet cut plate and turned boss will be a welded assy in Grade 5 Titanium, will need to fit a helicoil to stop the thread seizing as ti and steel threads don't mix well
using a high strength/precision motorsport M14 X 1.5 rose joint
not going with the ERP turn buckle quick style adjustment as lightweight for my application out ranks speed of adjustment.
total weight is 0.6kg compared to the 1.44kg Porsche bushed spring plate but I'm sure this will go up a small amount as I check the strength, stiffness and stresses
Could be made a lot lighter by setting the car up with an adjustable spring plate, dialing in the required toe and camber settings. Then taking the dimensions for each side and make a one peice spring plate with press in uni-ball. This is how WRC teams do it but well out of my budget.
if anyone is interested in a pair in titanium or steel let me know and I may get more than one pair for myself made
Just curious, will you use Anysys or Abaqus for your FEA? We have both licenses at work, and I'm guilty of doing a bit of analysis on my custom parts after hours haha!
I look forward to seeing the finished weldment, titanium can be a bit tricky as you no doubt know.
Thank you very much for the interest, confirms I'm not alone in wanting something simple and available Europe side of the pond.
I will reply to uou all individually as soon as I get some prices. From the interest so far I think a run of 10 sets should do and I will offer these in the order of who expressed interest first.
Jut to note there will be none of the usually titanium tax added to the titanium versions the only extra in price to the steel version will only come from the additional manufacturing costs.
jstyer, at the moment it is sized from the steel OEM part, I'm pretty sure we use both systems at work but for this I will use Catia FEA along with some simple hand calcs. I will try to make the weak link in the whole system the bodyshell mounting M14 bolt in single shear, better to break a bolt than cause bodyshell damage or break a swing arm or spring plate.
You are correct about titanium welding being tricky but I have an excellent titanium welding specialist lined up, they do all the titanium welding for the Ferrari F1 team and beautiful Ducati specframes. I have worked with them on some previous projects, they are artisans and I've never seen better titanium welds.
To achieve the strongest weled possible I will specify this part is welded in their argon (think this is the correct gas) pressurised welding chamber. Best described as like a fully sealed shot blasting cabinet with built in sealed rubber gloves so you can handle the parts but with a full argon gas atmosphere inside and a TIG welding set up rather than purging the part locally with argon out on a work bench.
Been busy this weekend despite being 1000 mile away from my car, threw a few tubes around a computer screen and created this to help me visualise everything and get a feel for the weight
its my own special brew of a mixture of RUF IRC centre section and WRC around the top of the A-pillar, roof diagonals and a rear semi space frame.
I'm also trying to stiffen up the front suspension strut top area. I've done a couple of versions of front diagonal cross bracing, not sure which one will miss the most things ie feet, steering column, heater system, wiper assy, front oil tank and fuel tank and anything else I've not thought of.
The rear diagonal and stays are all aimed at allowing the cutting out of the great big heavy rear damper upper mounting bridge thingy across the front of the engine bay. Its not just for weight reasons I'd like to remove it but I want to move the engine forward but the LH fuel rail clashes with it.
My original idea was to stiffen up the cill section between the A and B pillars with a deep section carbon structure but as I'm planning on having carbon doors I thought I'd add some low height door bars just to be on the safe side.
All tubes T45 and 40mm OD, blue is 2mm wall thickness, purple is 1.5mm and green is 1mm. All are sized from my best guess but I will get some stress analysis done before building.
Not happy when I did my first weight calculation as it came out at 57kg. I then found a few solid bars I had blanked from view and after deleting these rogue bars the weight fell to a more realistic 38kg
Hopefully is will come out strong enough on it own so I can replace the roof structure down the the bottom of the windows with a lightweight carbon structure.
03-24-2015, 09:01 PM
Porsche with a GT1 win in 97.
when I did my first weight calculation as it came out at 57kg. I then found a few solid bars I had blanked from view and after deleting these rogue bars the weight fell to a more realistic 38kg 
