4.2 Bodyoff Rebuild
Discussion
scerbera said:
I have a model for my new rear suspension set up, all measured on car and looking like there is plenty of room. Just need to add the mounting for caliper, then some time to make the parts. Model the front next and then I can start on chassis jig.
Interesting, what will you gain by this?I have been looking at ways to get the spring and damper more vertical to improve compliance and therefore ride and grip.
gruffalo said:
Interesting, what will you gain by this?
I have been looking at ways to get the spring and damper more vertical to improve compliance and therefore ride and grip.
Sure, as you mention, increased control of rear suspension, less flex in assembly and wishbones. Spring will be acting in correct plane relative to wheel. I have decided to draw up the chassis also, i'm half way through! It's a little tricky, but it means that in theory all chassis spars can be cut to exact length and angle etc without having to measure and eye it up. Should have tighter joints and less messing about. The chassis will all be tig welded anyway so the joints could do with being tight!I have been looking at ways to get the spring and damper more vertical to improve compliance and therefore ride and grip.
So, today I have got the diff out of the chassis, bolts were siezed it took ages. I have continued with the chassis drawing and have attached some pics below. I have also started to cut some tubes up, the ones in green are the ones i've done today, I got 12 cuts out of the holesaw. No pics as I left my phone at home. This is pretty much what a cerb chassis looks like, except for the additional spars at the front by the upper suspension pick up. I'm not sure it'g going to look quite like that, but it wont be like the TVR version either. I'm modelling up the front suspension next, and it will be slightly different with wider wishbones and again i'm relocating the shock mount just slightly.
One major change I have made is replacing the bottom rails with tube instead of box, so the rear lower outrigger sits slightly lower on the central tunnel. I have only roughly done the suspension mountings so that may look a bit different. The tunnel section of the chassis I also plan to gusset with 1.2mm steel to try to reduce the twist which will occur with such a narrow structure. The steel I am using is ropt510 and it is at least 2.5 times stronger than original. I am using 2mm and 2.6mm wall thickness and the chassis is coming in at 87kg with mostly 2.6 tube, and the additional support for rear shock. There are still some additional spars to go in to support this also. Does anyone know the weight of the original chassis?
I have also added in 2 spars where the front roll bar is, I am going to re site and re design the roll bar. Possibly make it adjustable in car.
One picture also shows the amount of planes that I needed to be able to create the chassis model, over 100.
Thanks for the comments, I have really enjoyed the last 4 days, I wont have quite so much time to spare now though.
One major change I have made is replacing the bottom rails with tube instead of box, so the rear lower outrigger sits slightly lower on the central tunnel. I have only roughly done the suspension mountings so that may look a bit different. The tunnel section of the chassis I also plan to gusset with 1.2mm steel to try to reduce the twist which will occur with such a narrow structure. The steel I am using is ropt510 and it is at least 2.5 times stronger than original. I am using 2mm and 2.6mm wall thickness and the chassis is coming in at 87kg with mostly 2.6 tube, and the additional support for rear shock. There are still some additional spars to go in to support this also. Does anyone know the weight of the original chassis?
I have also added in 2 spars where the front roll bar is, I am going to re site and re design the roll bar. Possibly make it adjustable in car.
One picture also shows the amount of planes that I needed to be able to create the chassis model, over 100.
Thanks for the comments, I have really enjoyed the last 4 days, I wont have quite so much time to spare now though.
I'll be following this with interest.
I know a good number of CAD packages myself (Autodesk mainly) and the only reason I haven't started doing something similar is because I haven't been able to find anywhere to put the car to work on it and take it to bits!
I've really wanted to model the chassis and then seek consultation on some ideas I've had for building something lighter and more robust to see if they're viable.
I then wanted to model the body properly but first, I need to find a unit in the midlands-ish. Apparently none exist, and you're in Wales right?
Good luck, looks like good work.
I know a good number of CAD packages myself (Autodesk mainly) and the only reason I haven't started doing something similar is because I haven't been able to find anywhere to put the car to work on it and take it to bits!
I've really wanted to model the chassis and then seek consultation on some ideas I've had for building something lighter and more robust to see if they're viable.
I then wanted to model the body properly but first, I need to find a unit in the midlands-ish. Apparently none exist, and you're in Wales right?
Good luck, looks like good work.
NuddyRap said:
I'll be following this with interest.
I know a good number of CAD packages myself (Autodesk mainly) and the only reason I haven't started doing something similar is because I haven't been able to find anywhere to put the car to work on it and take it to bits!
I've really wanted to model the chassis and then seek consultation on some ideas I've had for building something lighter and more robust to see if they're viable.
I then wanted to model the body properly but first, I need to find a unit in the midlands-ish. Apparently none exist, and you're in Wales right?
Good luck, looks like good work.
Thanks, yes I'm in Wales, luckily my business moved into a unit with ample space at the moment so I can do it. I know a good number of CAD packages myself (Autodesk mainly) and the only reason I haven't started doing something similar is because I haven't been able to find anywhere to put the car to work on it and take it to bits!
I've really wanted to model the chassis and then seek consultation on some ideas I've had for building something lighter and more robust to see if they're viable.
I then wanted to model the body properly but first, I need to find a unit in the midlands-ish. Apparently none exist, and you're in Wales right?
Good luck, looks like good work.
If you used T45 tube or 4130 I think you could save 25kgs with replacing the bottom rails.
I havent tried to save weight over original although the bottom spars save a fair bit, but I've added it back in. My aim is for a much more rigid chassis.
I was thinking similar and hoping to be able to find some savings like that. Whether or not they mean anything due to budget is a different matter.
Plus whether or not they're able to be felt is a different debate entirely, what with 40kg amounting to something like a 15bhp/tonne increase (Were the car to be a red rose at quoted power, weighing 1100kg before the weight saving).
So since they all weigh ~1200kg anyway, we're talking about 12-13 per tonne losing 40kg assuming max power, which is a 2.95% relative increase.
I've turned this in to something else entirely.
Point being - good work with the chassis and if you put some box geometry matching a known material thickness in at your measurement planes then boolean the tubes, you could probably get cut a template which slides together to hold the replacement tubes precisely where required for welding. Then sell the rig. But you already know that, which is why you've done it.
Plus whether or not they're able to be felt is a different debate entirely, what with 40kg amounting to something like a 15bhp/tonne increase (Were the car to be a red rose at quoted power, weighing 1100kg before the weight saving).
So since they all weigh ~1200kg anyway, we're talking about 12-13 per tonne losing 40kg assuming max power, which is a 2.95% relative increase.
I've turned this in to something else entirely.
Point being - good work with the chassis and if you put some box geometry matching a known material thickness in at your measurement planes then boolean the tubes, you could probably get cut a template which slides together to hold the replacement tubes precisely where required for welding. Then sell the rig. But you already know that, which is why you've done it.
Little progress update, have finished the suspension geometry now, got a little tidying to do with brackets and spars in the front but pretty pleased. Front upright design also. I think ill do the wishbones out of tube. I'm about to start drawing bells for the front and rear so that I can use bolt on rotors. Front shock arrangement gives a rising spring rate. Few pics below.
Jonbouy said:
How are you going to fabricate the chassis and components
For the wishbones I will make jigs, bolted where they need to be for geometry then Tig welded. I will soon be starting on the chassis jig, I will make it on reverse on my chassis basically,allowing for the suspension changes I am making. I am still playing about with finer details on suspension, I want to explore every option before committing to it. The rear is pretty much there now as are the chassis alterations.
The front I think the pull rod arrangement works, but taking into account the kpi and length of upper and lower wishbones, I think I'd prefer a pushrod. So I'm working on that to see which option is best, it may be a case of having spring direct as per original with different attachment points. What I am trying to do is reduce the load on the suspension so I can reduce weight and increase strength. I'm hoping to have this finished tomorrow.
I still have to site the calipers on uprights, I'm ordering disks e.t.c shortly.
The machined components are relatively easy as I have access to cnc.
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