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Chassis design
rpmagazine - 14/2/07 at 10:22 AM

Here is a copy of Godiva's chassis design, which is detailed in Race Magazine. Note some changes have occurred since this drawing as a result of working with a full sized mock-up of the chassis...what looks good on paper does not mean that components will match it!


rpmagazine - 14/2/07 at 10:40 AM

mock-up one:


SeaBass - 14/2/07 at 01:52 PM

Looks interesting...

What is Race magazine - an american publication?

Has anyone got a CAD copy of the chassis?

What bodywork is involved

What is the car designed for - a road / track toy or a formula racer type??


Doug68 - 14/2/07 at 10:25 PM

Race magazine is a Australian publication.
What you are seeing here is the 1st example in the prototype phase.
The engine BTW is a Mitsu 3.6L? V6.
I'm sure rpmmagazine will explain further...


rpmagazine - 15/2/07 at 01:26 AM

Seabass, Race Magazine (actually Race Performance and Car Constructor Magazine) is as Doug posted an Australian quarterly magazine that has been going for 2 years. I am the Publisher.
Project Godiva is the project car within the magazine and is an ICV (individually constructed vehicle) designed to meet the relevant australian standards so it can be run on the road. As such it is not intended to be a lemans style car. It is intended to be a car that you can drive to an event should you wish and it is focused at tarmac rallies (e.g. Targa Tasmania), circuit racing/sprinting, Hillclimbs etc.
There is no CAD copy of the chassis as it is constantly getting modified as the component list is finalised. I am in essance reverse engineering aspects of the above design as the final dimensions of components are realised. An example of this is the steering rack: 3 were tried, each with a different width and each required the front box and the cabin area to be changed to suit the new chassis dimensions.
There was the intention to publish a manual with a DVD with all of the plans on it so that they could be printed off full size on a plotter. This is on indefinate hold as the dreaded insurance issues have raised their head.
The dimensions are (note this may vary slightly as you would expect):
wheelbase 2570mm
rear track 1570mm
front track 1630mm
height 1250mm
weight 880-900kg
the engine is a Mitsubishi 3.8lt 6g75 with a 5 speed close ratio manual gearbox, which gives 175kW as std.


Ivan - 15/2/07 at 07:20 AM

An exciting project.

I'm always interested in these types of projects (as I am sure are many others) Please keep us updated on progress on this thread.


locost_bryan - 16/2/07 at 03:31 AM

quote:
Originally posted by rpmagazine
the engine is a Mitsubishi 3.8lt 6g75 with a 5 speed close ratio manual gearbox, which gives 175kW as std.


180kw in the VR-X and GT in NZ - exhaust changes iirc

Didn't Mitsi do a Supercharged engine for one of the motor shows?


rpmagazine - 16/2/07 at 08:58 AM

Yes, there was a supercharged 6G75 in the TMR 380, which is a motorshow special. The Sprintex kit for the 6G74 is freely available and can take power up to 280kW, but at these levels the transmission will require care and attention as the diff is a weak point. Mind you using the engine/box mid mount will change the loads etc on it, so the issues may be different and only time and failures will show what needs to be fixed.
I expect a new intake cam, mild port work and better ex/induction will give around 205kW, though of course this will not be legal. A more radical rebuild should net 220kW or so, but it gets expensive, say a $6k modification not including ECU.
To be honset the money is far better spent on very good dampers as these will allow more speed and better braking, hence my current thoughts are leaning towards Penske dampers.


rpmagazine - 18/2/07 at 02:27 AM

FWIW the Race Magazine looks like this:


[Edited on 18/2/07 by rpmagazine]


rpmagazine - 17/7/07 at 11:55 AM

Time holds still for now man and especially a car builder!
Here are some more picks showing some progress...it has moved on from here and the mock-up is almost finished.


Doug68 - 18/7/07 at 11:01 AM

That's coming along, it looks good and tall though, whats the expected height going to be?

I'm sure you've thought of it but the diagonals coming down from the center of the windscreen look like they'll be argro on the legs.


rpmagazine - 18/7/07 at 12:59 PM

The looks are deceiving, as the car will be 911/cayman height at 1280-1315mm.
The diagonals are also far worse looking than they really are, there is plenty of room for me and I cannot expect anyone else will need more room!
The front and rear structure ties in nicely, but I cannot show that yet. The side structure will likely change to where the tape is. Plan is to exceed 60kN/deg for the chassis.
The mockup structure was changed to increase the stiffness. I adapted a trick from Ron Tauranac, which was to make the structure and then run tightish tape lines where I thought tubes should go. I then pushed on various points to simulate the running forces and the tapes went tight/slack at different points. This showed where structure needed to be added.
The main cage tubes are 50mm cds and the sides are 50mm SHS 1.6mm wall 450mpa with the smaller tubes generally 40mm of the same.

[Edited on 18/7/07 by rpmagazine]


Doug68 - 18/7/07 at 01:45 PM

Where'd you get the 450mpa steel from?
I had to go with 350mpa here in WA,
The 450mpa grade material I found in catalogues was One Steels HiLite series which seems basically impossible to get over here.


rpmagazine - 19/7/07 at 09:28 AM

Hi Lite is available in Vic. The performance of Palmer tube mills (now Smorgon steel) dual grade 350Lo/450Lo is also good and it is supposedly easier to weld. The Hi Lite is available in 1.2mm wall in the catalog, but finding it in small quantities is the trick. Smorgon's will only sell in a bundle as a minimum and no one need 50 tubes 6m long!
Mind you if you are in WA then Ayres Panels is 'local'.


rpmagazine - 27/7/07 at 11:52 AM

Doug, I've been told that there is a 450mpa Duragal in 1.6mm wall. I've been given some samples of it and the galvanising zinc is also on the inside of the tube...good for chassis survival.


Doug68 - 27/7/07 at 02:52 PM

That's a bit blinking late for me now!


rpmagazine - 27/7/07 at 10:49 PM

Coming on there!...have you sat in it yet making brumm brumm noises? Maybe that is just me and my two young boys!
How are you holding it down to the checker plate?
I was planning to tack weld tubes down.


Doug68 - 28/7/07 at 02:36 PM

It tacked down to the checker plate in various places. Using the TIG to do that for some reason was just not happening, so I broke out the arc rods and got it tacked down that way.

Just tonight I finished tacking all of the floor tubes in place. Now I get to start on fully welding it together.


rpmagazine - 29/7/07 at 10:37 AM

Interesting. Did you find it moved much from the weld and weld contraction when tacked down?
BTW Godiva's rear suspension should be heading down the path as per this image:




I've also decided to follow the advice I've been given and will go for suspension bushes on the inner pivots of the arms, though the cost saving is not as good as you might think.
This will lessen the impact/shock loads and will allow development without the mount/arm/chassis fatigue concerns.

[Edited on 29/7/07 by rpmagazine]


Doug68 - 29/7/07 at 12:56 PM

When tacking it down I was unable to detect any movement off alignment marks. I'm sure it did move but not enough to measure.
Obviously I was aiming to get as little heat into the tube as necessary.

I'm using these for inner rod ends on the to "A" arms...



My reasons why are here

[Edited on 29/7/07 by Doug68]


kb58 - 29/7/07 at 05:28 PM

Those will work fine as long as they aren't being asked to move off centerline much.


rpmagazine - 29/7/07 at 10:51 PM

They seem a good compromise and get away from the jarring and wear issues that some rods ends develop.
I may end up using MX5 front wishbone bushes in most places, though the lower arm may have added longitudinal compliance.


Doug68 - 30/7/07 at 12:49 AM

Yep in the design my end should need to only rotate about the bush.
If it needs to do anything else its a stuff up on my part.


rpmagazine - 30/7/07 at 10:45 AM

well there is a little bit of compliance in that bush. Getting them to line up perfectly can be quite tricky. According to some you can tailor the compliance of a poly bush by removing some of the material or by casting your own dual durometer bushes...quite a bit of work though and potentially hard to replicate when they wear out.


rpmagazine - 12/8/07 at 12:12 PM

Some updates...and some details I am not really happy about:

The tape represents structural members and suspension components.

The inner bit of tape attaching on the bottom tube is a removable diagonal from the front mid tri-node.

Really not happy about the dogleg in the structure...it would not be made this way, but that gearbox creates some problems!

[Edited on 12/8/07 by rpmagazine]


Doug68 - 12/8/07 at 02:50 PM

I hope this comments will be helpful...

Blue lines delete.
Red Lines add. Verticals and horizontals 50x25 and bracing 25 square.

"A" I don't see where the load from this can go? you'll be sitting the other side so any sort of structure will be hard to do there I'm guessing?

"B" Lower the whole frame and mount the suspension brackets on top to get rid of the dog leg?

"C" I suspect the control arm would clear a lowered frame section? So the bottom tube can be straightened out.

My other lesson for the day is don't make tube join angle too acute or they become a PITA to weld.

[Edited on 12/8/07 by Doug68] Rescued attachment EDIT.jpg
Rescued attachment EDIT.jpg


kb58 - 12/8/07 at 06:26 PM

After you tentatively place the tubes, make sure there's still room for your tires! The foward lower tubes look like they're getting close.


rpmagazine - 12/8/07 at 10:33 PM

quote:
Originally posted by Doug68
I hope this comments will be helpful...

Blue lines delete.
Red Lines add. Verticals and horizontals 50x25 and bracing 25 square.

"A" I don't see where the load from this can go? you'll be sitting the other side so any sort of structure will be hard to do there I'm guessing?

"B" Lower the whole frame and mount the suspension brackets on top to get rid of the dog leg?

"C" I suspect the control arm would clear a lowered frame section? So the bottom tube can be straightened out.

My other lesson for the day is don't make tube join angle too acute or they become a PITA to weld.

[Edited on 12/8/07 by Doug68]


A attaches to a cross beam that is also the apex of a transverse box section made from Al honeycomb panel. This boz section houses the 75lt fuel tank on the passengers side.
B, despite my great reservations I am considering a fabricated upright. I can construct the dogleg section (under the gearbox) such that there is minimal loss of stiffness, but it adds weight and is less than elegant. The point B you note has a removable diagonal from the mid trinode, not shown in this image...I'll try to find an image of it.
Not quite sure what you mean by C. The bottom tube is straight. The forward leading tape represents the forward leg of the L arm and the mount would be just in front of the angled tube. There is another tube not shown at this point that mirrors the diagonal and runs to the center of the car.
Agreed re the welding, the mockup has already solved many of these issues. The rear structure will be a mix of round and square tube.
KB it is deceiving as there is approx 5" of clearance. The width of the block of wood represents the absolute maximum tyre I would consider possible at 335 wide and that just clears. I am intending to use 255.40.17 at the rear.

[Edited on 12/8/07 by rpmagazine]

[Edited on 12/8/07 by rpmagazine]

[Edited on 12/8/07 by rpmagazine]


TheGecko - 13/8/07 at 03:54 AM

Neil,

Good to see you making progress. Also good to see I'm not the only one mocking up in "structural masking tape"

Dominic
Mock up engine bay
Mock up engine bay


rpmagazine - 13/8/07 at 04:10 AM

Not at all...you gave me the idea. I did find a secondary benefit though: I made up the basic structure with flexible joints (hot glue and tape) and ran tape lines where I thought tubes needed to go. Then I pushed on various nodes simulating loads/forces being fed into the chassis. I then watched which tapes deflected/changed and this told me where the structure needed to go. It saved me a HUGE amount of time and work!


rpmagazine - 22/8/07 at 11:56 AM

Rear structure update: The joy of non asymmetric tetrahedrons in a non planar truss -



Spyderman - 22/8/07 at 05:23 PM

I am a little confused. If all of those tape lines are going to be structural tubes how are you going to get the engine in and out?


rpmagazine - 22/8/07 at 10:20 PM

Yes the tape lines represent structural tubes. There are about 5 options, but the two under serious consideration are having the majority of the rear structure detach from the main hoop etc. The second is that the lowest/floor section will detach from the firewall and from immediately prior to the first transverse arm, which means the complete drive train can drop out the bottom of the car...minus driveshafts.

[Edited on 22/8/07 by rpmagazine]