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Wow, really looking forward to how this turns out, I have always liked the idea of an old "stock car" style street rod (wide steels, radiused guards, no bumpers) that could actually hold it's own on a track or hillclimb. It looks like you've read my mind to an extent, top form!
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jonomisfit
Club Retro Rides Member
Posts: 1,764
Club RR Member Number: 49
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Aug 27, 2012 20:15:01 GMT
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Right so after a few issues involving my PC, an application of a 64 bit operating system, a lack of compatibility with the cad package, finally tracking down something that'll work for me I got back on the chassis design. After much faffing with the FEA package I figured it wasnt going to work properly so re modeled the whole chassis again this time as weldments (upside being is I get a free cut list) and used a beam type FEA. Its still a work in progress. There may be a complete excess of triangle spamming which I need to cut down a lot. As my mate says, presently not very elegant.  Stress xxx Displacement xxx I have a lot to tweak. will update when i've done some more work. We'll see if photobucket shows them this time..... |
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Last Edit: Sept 12, 2012 20:05:01 GMT by jonomisfit
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jonomisfit
Club Retro Rides Member
Posts: 1,764
Club RR Member Number: 49
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Aug 30, 2012 19:41:10 GMT
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Last Edit: Aug 30, 2012 19:43:32 GMT by jonomisfit
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Aug 31, 2012 19:53:23 GMT
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Looks interesting. What did you do to calculate the loading forces on the chassis? Where are the forces being applied to and which parts are being constrained?
James
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jonomisfit
Club Retro Rides Member
Posts: 1,764
Club RR Member Number: 49
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Sept 2, 2012 20:21:57 GMT
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I'm not doing a proper FEA study, just using it to do relative comparisons to see what gives greater stiffness, and what causes high stress concentrations. I used 3g bump acting on the wheel and took an estimate of unsprung mass for the corner. I then coupled it with an inverted load on the other side to give the twist. Constraints are taken as the 8 corner points of the front suspension box. Not really how it'll work in the real world but useful to understand the above. I spent the afternoon looking at wrc cages etc for inspiration. Then tried some different options. <it's still not linking the pics properly. not sure if the file names are too long or what> s234.beta.photobucket.com/user/jono_misfit/library/JP%20Morris%208With all the tubes the weights going up a lot (CAD weight of 120kg's) + steel shell on top, this is getting heavy. Next step is to try and work out what is redundant, what can be changed etc. When compared with space frame race cars (not wrc's) i've got a lot more tube that others tend to. I need to look at the tunnel as its not carrying much of the load. If its redundant i'll replace it with a more flimsy structure. Front bulkhead is far to over complicated for its own good too. |
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Last Edit: Sept 2, 2012 20:25:04 GMT by jonomisfit
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Sept 2, 2012 21:55:45 GMT
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Looks interesting Wouldn't it be an idea to build a simple bulkhead structures (front and rear) from the same tubing that is being used for the main runners? A quick torsion test could be done if you constrain the frame on the 3 suspension points and put a load on the 4th one. However numbers will be off compared to real life testing  |
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 Click picture for more |
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jonomisfit
Club Retro Rides Member
Posts: 1,764
Club RR Member Number: 49
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Sept 3, 2012 16:51:42 GMT
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I think when compared to a physical torsion test, my present model isn't too bad (replicating the restraints, although not the actual loading). This is roughly the setup that's used to determine deflection under load.  Trying to carry loads around the gearbox / bellhousing opening is what's caused my one to turn into the present mass of tubes. I tried a simpler structure but it was flimsy when avoiding the gearbox. I need to make some more representative models of the engine / box as this will help me on how much space is actually needed. My present model of a massive American V8 and box is driving a huge opening and is probably leading to more restrictions that I need. I might go back to the start and try reducing the tube size down and going for more of a lotus 7 style chassis with cage on top, rather than my present cage is the structure method. Could end up lighter, but then again might not. |
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jonomisfit
Club Retro Rides Member
Posts: 1,764
Club RR Member Number: 49
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Sept 12, 2012 19:43:28 GMT
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Tried a different style chassis. This is much more kitcar inspired. Displacement for same load was good.  Stress was a bit higher though in the front of the frame  And this is for a chassis that is 45% of the weight of the other design. I've got another different style i'm going to look at, then will try choose one and develop it further. Seriously, whats the issue with photo bucket? Am I using too long a file name? |
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Last Edit: Sept 12, 2012 19:48:46 GMT by jonomisfit
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jonomisfit
Club Retro Rides Member
Posts: 1,764
Club RR Member Number: 49
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Sept 16, 2012 17:45:31 GMT
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So been playing around a bit more with different designs. This is a hybrid between the kit inspired and previous design.   and then with the load / fixtures reversed (and increased) with a bridge over the engine     Tube city.... but its 45kg less in weight than the earlier design at about 98kg. I've also spent ages today looking at different engine options for the car. At the moment i'm thinking about a jag alloy v6 or v8 as an option for it. We'll see though. |
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jonomisfit
Club Retro Rides Member
Posts: 1,764
Club RR Member Number: 49
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Sept 29, 2012 16:24:50 GMT
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So finally got the caddy out of the workshop (see post 1) and took it for its MoT test (passed with only a bulb change) so cleaned up the place, put up a few extra lights and started thinking about actually starting the Morris.   I might actually go for the lifted look....... or maybe not. Outer sills are in poor condition (can see from the outside), and the inner sills are gone, although I was expecting this.  Is that 3 layers of badly made overlaped plates I see, why yes it is. The state of all attempted repairs on the car are very poor.   This was the best and its wasnt very good. So wise spark had also welded the body to the chassis at one of the "repairs". Back panel is gone.  And so too is the chassis.  Paper thin all the way round. Just as well I wasnt intending to re-use it. Someone previously had made a nice job of rubbing down the exterior and painting with Chassis paint to make it all look good though........  Tomorrows job is to make a screen guard for the caddy and start work on the flat table to make the morris chassis on. Oh and still a load of CAD work to do to pick a suitable structure with minimised tubes. |
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With those CAD pictures, are you aiming for it all the be blue or red? I'm not familiar with them, so I'm not sure what I'm looking at.
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jonomisfit
Club Retro Rides Member
Posts: 1,764
Club RR Member Number: 49
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If the frame was transfering loads equally amoungst all members, all would be red at the same time. But as the fame has to cope with different loading regimes this is unlikely.
What i'm mainly trying to do is see is if any elements have excessive stress levels relative to others (red compared to blue).
With the constrains i've used though, the nodes that are fixed (generally the 8 corners of the suspension boxes) at the point you twist the chassis suffer significantly higher stress than they will in reality.
If I ramp it up to a more realistic figure for the loads i also want to make sure that nothing get to within an appreciable % of the yield stress of the material. i.e. I don't want the chassis to be in danger of permament deformation if a wheel hits a bump. Its no-where near though, which is good.
I also want a stiff chassis so the suspension works propperly.
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Okay, that makes more sense of it to me. Always something new to learn around here.
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drdick
Part of things
Posts: 359
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What sort of material/section properties are you using? At the moment your stresses are very low (26MPa if I'm reading that right) so I assume the design can be pared down significantly. I'm not familiar with whatever FE package you are using but are you checking for buckling of the tubes? I'd assume that would be the failure mode for something like this?
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lippyp
Part of things
Posts: 29
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I'm sure I recognise that car from a magazine some years ago, possibly Practical Classics, as belonging to one of the staff members. Its the skull and crossbones on the door and that chequered pattern behind it thats ringing bells. Should be a very interesting project.
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jonomisfit
Club Retro Rides Member
Posts: 1,764
Club RR Member Number: 49
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The stress is so low due to the low load I put on the chassis, it was really just for indication of relative to each design what was causing greater stress concentrations. When i've put a more realistic loads in its a much more realistic figure, but well within the yield limit still. There's still a load of rationalisation to be done on the tubes though.
Material is mild steel and sections vary from 50 x 50 x 1.5 down to 19mm OD x 1.25. Hoop is 45mmOD by 2.5mm CDS.
I've been concentrating on stress levels at the joints as I want to ensure it shouldn't suffer from fatigue cracking, which is what kit cars normally do. The package gives the buckling factor with the results and all seems good on that front too.
Car was owned by David Lillywhite of Practical Classics in its dim and distant past.
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jonomisfit
Club Retro Rides Member
Posts: 1,764
Club RR Member Number: 49
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Oct 21, 2012 20:45:19 GMT
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Did a little bit on the morris today. I took the sunroof out, as it was looking a bit thin on the back edge.     In general the roof is in not too bad a condition although this edge which is night on inaccessible isnt so good.  I also started the build table for once I get the steel. Its pretty rigid and will help getting the chassis straight.  |
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jonomisfit
Club Retro Rides Member
Posts: 1,764
Club RR Member Number: 49
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Nov 25, 2012 20:24:42 GMT
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After getting way laid the last few weeks doing some decorating in the house I finally got chance to work on the morris. This then got way laid by a water leak into the cab of the pickup. After stripping out the dash to find out the problem I re-set the rubber and filled it with sealing compound. Fingers crossed. By the time it all went back together and running I didnt get much time on the morris. Still, all this turned up  to be turned into hotrod. Started marking out the chassis lines   Before starting on the main cockpit rails.   Having pushed the rails out as far as I can to give as much room as possible, its still going to be very very tight around the foot pedals to gearbox bit. Will see how it develops. I've worked out a load of the bits I need to get and started doing some drawings. |
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Last Edit: Nov 25, 2012 20:25:37 GMT by jonomisfit
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Nov 25, 2012 21:14:27 GMT
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I think its gonna turn out great....
I'm making a bead roller(home made)...i got a 8mm thick plate 1300mm long and 400mm high but at the end of the cut gap its a little of line...probably i will have to hardened it or you got another idea maybe ?
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jonomisfit
Club Retro Rides Member
Posts: 1,764
Club RR Member Number: 49
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Nov 25, 2012 21:41:33 GMT
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It depends what your wanting to roll i'd guess. If its mainly aluminium then unhardened mild steel rollers might work ok. They might event work on thin mild steel as well but i'm guessing will wear more heavily over time than hardened ones.
You could try buying some harder steel and machining the dies from that but cutting will more difficult and will wear the lathe tools more heavily.
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