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I love the idea of removing the cross brace at the front of the engine bay.... Going to be awesome if possible.
I'm surprised you're going with steel door bars. Since you're not running heat, do you think you could possibly go with composite/honeycomb members inside of the sill? You'd have to cut into them, and re-weld, but man oh man would that be some cool and stealthy protection.
thanks for the words of encouragement, I'm not completely happy with the rear diagonals and cross bracing as I don't think the design I've done is the best for supporting the engine weight.
jstyer, like your thinking and I have considered doing exactly as you suggest but as I can't afford to make autoclaved structures I would rather go safe and put my faith in some good olde fashioned simple steel tubing.
Got some stress results for the titanium spring plate design.
When I design parts that require stress analysis my approach is to hopefully create a shape that is that little bit under strength and stiffness. The stress analysis then shows you where you need to add extra material to the part which in turn ensures the part only has very little extra fat on it for the ride.
As I have no suspension loads my original aim was to have a spring plate that was an order of magnitude stronger than the mounting bolt ie the M14 mounting bolt to the car would fail first. To break this M14 10.9 grade spring plate to chassis bolt requires a 5000kg load. As the shear plate will never see anything close to this load other than in an accident I used 5000kg to check the spring plate.
As a first design iteration I used the same 6.35mm / 1/4" thickness as the original Porsche part on the plate and around the threaded hole. Keeping the both welded parts a similar thickness also helps to manage the thermal stresses between the two parts during welding.
The results for peak stress and deflection for a tensile load ie stretching the part are as follows.
First picture, shows how the part is held, I considered the swing arm mounting bolts bolts hit the end of the lower slots and the edge of the upper hole. In reality the spring plate is clamped with a thick washer on one side and against the alumnium swing arm on the other side so the bolts should never bottom out on the ends of the slots. The clamping constraint is a far less aggressive way of constraining the part but its safer to be more agressive than real life when doing analysis. The tenisle load is applied to the internal thread on the boss.
The next picture shows the peak stress in the upper view, what you are trying to do is to stay within the maximum yeild stress, higher than the yeild stress and the part is starting to become permaently stretched up until it breaks when it hits the ulitmate stress value. You also try to reduce any hot spots so there is a a smooth transition between the various stress levels arounfd the shape of the part. The lower view shows the deflection, in this case the measurement that is stretching by
Looking at the colours and stress/deflection values you should be able to see that the left part of the plate between the 3 mounting holes/slots is very lightly stressed.
Basically everything is fine, the peak stress is well within the stress properties of the titanium and the titanium part would stretch 0.21mm longer, while the steel part would be around 0.11mm. This deflection is nothing compared to the rubber bushed Porsche part.
What next, well a couple of things, I need to check the deflection in compression ie trying to squeeze the part along its length as this will be the weaker. I'm also going to try a lighter weight design and change the plate thickness to 5mm to see what effect this has. Also from the above stress plots you should be able to see that the areas around the mounting slots and hole on the right hand side of the part is very lightly stressed so this is an area I will target to remove weight. I will post up a picture of my modified design for a spot the difference challenge and then later when I have more stress results I will post up the stress plots so you can see how the thickness and shape changes have influenced the stress distribution and deflection.
I have also got some cost estimates, for the steel part it will be between £550-575/pair including high quality rose joint, corossion coating and mounting bushes. For the titanium don't ask but I'm working on trying to get the price down.
I know I'm crap at explaining things but please ask away as its always good to question things when designing
sweet lord - the Wizard of Oz himself wouldn't reach this level!
Just to make sure I understand, blue is faster right?
nope red is fastest but on the top view (see 2 posts up) white is happy, red is angry and blue are chilled zones
In the below view the transparent shapes are my original design and green shapes are version 2 design, also not so visible is I've reduced the titanium plate thickness from 6.35 to 5mm
total weight now is about 0.45kg instead of the Porsche 1.44kg
working on an acceleration of 1G which is well on the generous side the compression load is only 375kg so little fear it will buckle or distort by too much
I will post up some stres plots so you can see if I have made the plate too angry in the high stress areas
Can't wait to see the plot in compression. I like the generous removal of material on the mounting hole side!
I'm guessing you're still under yield at the top mounting hole, even using the more aggressive constraints of the first model. With a pinned (bolted) connection and washer, I'm sure you're still kosher. No doubt you're well within limits at the inside of the cut feature on the monoball side.
Some people may have spotted but one aspect of my build I am trying hard to keep to (when budget allows) is to use upgraded components that are made by companies that have supplied F1 world championship winning teams eg OMP, Alcon, BBS etc. I am a firm believer racing makes the breed stronger.
This is why I going off on a completely random aspect of my build which I was going to leave until much later as its a long way off from happening.
Basically this post is all about paint, it is heavy, just lift a tin to get a feel of what I mean. The first time I realised how much weight it can add to a car was when I worked on the McLaren F1 road and Le Mans race cars, we had the road cars painted by a quality coachwork company that had zero racing car painting expereince and the GT1 race cars painted by another company that used to paint the Gordon Murray era Brabham F1 cars of years gone by. The difference in weight of the paint added to the car by each company was astonishing, kgs and kgs different, from memory easily +10kgs.
Even the lightest paint coverage on todays F1 racing cars still weighs a lot, approx. 0.2kg to 0.3kg a square meter depending on how skilled the paint shop is and what colours are used. Multiply this by the 10-12 square meters of painted area you can see how it adds up, on an LMP 1 car the total would be a lot more. Even the painting of a wheel will easily add over 0.1kg of extra unsprung weight compared to anodised or polished finish. When fighting to save every gram of weight this is the reason why many parts of F1 racing cars are left as an unpainted bare carbon finish.
Paint doesn't add performance but is a marketing must have, the right colours look cool too.
Colours also influence the weight as different pigments have different densities and require different %'s of pigment. Also the colour affects coverage thickness to achieve an accceptable finish. Metallics weigh more than solid colours, someone once told me up to 10-15% more but I can't verify this.
I had lunch yesterday with a friend who works for a company started up by a friend of Enzo that back in 1975 created an ultra-lightweight red pigment that became the secret ingredient of the paint used on Niki Lauda's world championship winning Ferrari.
Here is a Mr. Lauda out for a Sunday drive in his Ferrari 312T
As you do over a beer and pizza we covered all sorts of random bull$hit subjects , he casually mentioned he had some lightweight paint I could have. Now the colour choices for my build have always been black and white as in colour options so when he said he 10ltrs of both colours in a special lightweight PPG aerospace paint system I couldn't say 'YES Please' fast enough.
Now to my final choice of colour well there is only way to chose and to let the colours fight it out between themselves so I will get some paint samples done to help me make the right choice. I have plenty of other tricks up my sleeve when it comes painting time but I'll leave this for a later show and tell post.
Last edited by Captain Ahab Jr.; Apr 17, 2015 at 05:27 PM.
Nice! I love how thorough you are with this build... No stone unturned.
I thought you'd get a kick out of this link. Not quite as sophisticated as your build, but very well done in my opinion! You guys across the pond put together some killer cars.
Keeping true to my theme of lightweight and buying upgraded parts from companies that have supplied F1 world championship winning teams I ordered 2 sets of these yesterday
Scroth Profi ii Titanium seat harnesses, only weigh 1.41kg each
The titanium bits
Lightweight snap buckle to anchor to the lap straps
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