4.2 Bodyoff Rebuild

[scerbera]

aide said:

I'm really enjoying this thread.

It's really great when people use their expertise to make things better!

Have you considered using titanium?

ti, no I haven't really due to cost, but could be cool for suspension maybe, i'll have a think about that.

[scerbera]

So I'm still working on the suspension models but maybe 95% there now. Tonight I have ordered all the parts I need to buy for suspension. My uprights have changed a little, I have saved 1kg off the rear and could go for more. Below are some basic stress analysis simulations. I have a factor of safety of over 10 on each upright with between a 2000kg and 3000kg loading, so very safe, although it is a very simple analysis. Loading on rear is 500kg on each bolt point from bearing, 500kg on face of upright and 1000kg on shock pickup. Front is 500k per bolt and 1000kg on face. These loads are clearly in excess of what you would get on the road. Material was 6082T6 which is cheap and easy to get, but I do have some blocks of 7075T6 which I may use, and that is significantly stronger, but doesn't hold up to fatigue so well.

I will add in mounting points for calipers and steering on front in the next few days. I was going to go for my own stub axle on the front with bearing set in the upright, but I figure for time it is easier to use existing bearing setup.

I cut a few more tubes today ready for new chassis, still yet to start on the jig. I did cut the existing chassis in a few places to inspect and it's much better than I thought. It is all light surface corrosion. I guess I will have it blasted, then repair if needed, and powder coat, have no plans for it but may need it for something. Or I would be willing to sell I suppose.

Braking is getting an overhaul, 6 pots on front, 4 on rear, hubs and rotors but not floating i'll go for solid bolted. As I've mention I don't like the pedals and have that figured out, will post pics when ready. I have an hour spare tomorrow so will do a bit more on the chassis. My AP units will be surplus to requirements.

[FarmyardPants]

I could model the chassis in Solidworks, but wouldn't be able to do anything with said model other than spin it around and look at it (and run some stress simulations).

How do you plan to use your models, do you have access to CAM machinery that can mill parts from them?

The pics look great!

[scerbera]

FarmyardPants said:

I could model the chassis in Solidworks, but wouldn't be able to do anything with said model other than spin it around and look at it (and run some stress simulations).

How do you plan to use your models, do you have access to CAM machinery that can mill parts from them?

The pics look great!

Yes I have a 4 axis cnc luckily.

[portzi]

scerbera said:

FarmyardPants said:

I could model the chassis in Solidworks, but wouldn't be able to do anything with said model other than spin it around and look at it (and run some stress simulations).

How do you plan to use your models, do you have access to CAM machinery that can mill parts from them?

The pics look great!

Yes I have a 4 axis cnc luckily.

So CNC milling out of a solid billet. So you will surface model it in feature CAM, then pic surfaces pieces to mill.

3 of 4 setups on milling machine, l hope all goes well first time

[scerbera]

Sure, the uprights are relatively simple. For front will cut dovetail on one side of stock, then clamped into a 5 axis vice, which gives you clearance on all other faces. First side will be the outside of upright, normal cutting and contouring, will use the bolt holes initially reamed to 6mm, can then flip part and locate accurately with out clocking in. This side then finished, which will leave lower ball to do which is no problem as its perpendicular, upper is angled 9 degrees I think off the top of my head, so will need to make a jig for this. Then back on to front and take the 6mm up to clearance. Fairly similar for rears.

[Jonbouy]

wow, just my type of reading, some real interesting engineering designs and processes, would love to be able to operate and design components in CAD. scerbera, have you worked any costings out? I must cost a fair bit for a solid block of aluminium?

Great thread.

[scerbera]

Jonbouy said:

wow, just my type of reading, some real interesting engineering designs and processes, would love to be able to operate and design components in CAD. scerbera, have you worked any costings out? I must cost a fair bit for a solid block of aluminium?

Great thread.

Thanks, the front billet is around £85, and rear probably £120 for the raw stock. That would be 6082T6 which is very common and a good material. I will post up some videos when I machine the uprights.

[scerbera]

This evening I've modeled my front bell for the discs I'm going to use. I think I will get these anodised red to match the car, not this red exactly but you get the idea. Bore hole is incorrect i'll measure bearing tomorrow. I'll also probably pull the taper in earlier to reduce a little more weight.

Edited by scerbera on Wednesday 18th January 00:50

[FarmyardPants]

Looks like a bottle top :-)

[julian64]

Just a quick question, and I could be wrong as my abilities with solidworks aren't anywhere near as good as yours.

The upright you have done stress analysis for shows a lateral force applied evenly.

When I have done this in solidworks (not with an upright, but modelling other components) the bit that kills me is the bolt holes. And its the bolt holes that seem to be the bit that it always breaks at as I increase the force. From the pattern you have it looks like you haven't fixed the bolt holes for your stress analysis so you don't have the red warnings all around the bolt holes that I get. Is there any reason you've done it like that?

[scerbera]

julian64 said:

Just a quick question, and I could be wrong as my abilities with solidworks aren't anywhere near as good as yours.

The upright you have done stress analysis for shows a lateral force applied evenly.

When I have done this in solidworks (not with an upright, but modelling other components) the bit that kills me is the bolt holes. And its the bolt holes that seem to be the bit that it always breaks at as I increase the force. From the pattern you have it looks like you haven't fixed the bolt holes for your stress analysis so you don't have the red warnings all around the bolt holes that I get. Is there any reason you've done it like that?

For some reason the arrows indicating force on the bolt holes aren't in the picture, but they are there. For the front I put 10000N on the face which, then 5000N pushing upward on each bolt hole, it's hard to model as the bolt doesn't act on it like that, but it's probably near enough to get an idea.

My fixed points are the bolt hole top and bottom. I'm not sure how to go about modelling dynamic stress, but this is 2500kg going through it and has a factor of safety of 10.

For the rears same setup, but I also have 10000N on the shock mounting. If you look again at the rear von mises pic you can see some red around a lower bolt hole.

[scerbera]

Yesterday my rod ends and spherical balls arrived for suspension so can make a start on that when time permits!

I have ordered 309/21 discs for rear and 331/32 for front. Also some bits to rearrange pedals, I need to see if it's going to work, I think so according to my measurements.

I do have a question for anyone reading with prior knowledge, if I go for 4 pot at rear and 6 pot at front, will I need to change master cylinder bore? Or does anyone know typical distance before pad engagement?

Also I am unable to find the power assist ratio for the brake servo, does anyone know what it is?

[Poopdog]

What are you doing with the pedals then?, like you I'm not keen on my pedals either as in my case they just feel wooden and cumbersome , what make calipers are you going for then?

[scerbera]

Poopdog said:

What are you doing with the pedals then?, like you I'm not keen on my pedals either as in my case they just feel wooden and cumbersome , what make calipers are you going for then?

Ah well, I was going to go for Wilwood, and I may still, but last night I decided to draw a caliper, which I've done and I'm happy with it, so the rear is done.

I'm going to use a wilwood pad, something like 120*62 for rear, and 150 wide on the front. Hoping to draw that tonight.

I've ordered a pedal box as it's not too dear to justify, a wilwood unit, there appears to be plenty of room if you take the existing structure away. I will probably modify it, add appropriate brackets for new pedals and refit.

The brake is a double master cylinder with a bias bar so I can dial in the brake balance. The master cylinders will be easily accessible I believe, they are further inside the cabin, as will clutch master be.

I plan to run remote servo unit in place of existing unit.

For throttle I will also be moving and changing action, I don't like the throw of it at all. It will be shorter.

[Poopdog]

I think your right about making your own calipers as they don't look that hard to make compared to the other parts you are designing.
And I agree that there is too much travel on the throttle which I know was meant to stop people with a heavy foot but it feels unnatural having to push a throttle that far especially compared to modern cars throttle travel.
I reckon if you do pull this off successfully there may be a queue of people after your expertise, me being one included if you so wish.

[Outl4w]

I want to buy all of this! wicked thread - amazing work. Please keep all the pics and details coming.

J

[scerbera]

Thanks for kind comments. I'm open to making things for people once I've put this together so I guess we will have to wait and see how it turns out.

A few bits arrived today, braking parts and pedal box. I have nearly managed to get the existing pedal assembly out, the new one will fit great and make everything more accessible. The brake is dual master with bias bar.

I've done a little assembly of the rear upright with caliper, disc and bell. The new rear pads are enormous compared to standard, possibly 3* as big, around the same size as existing fronts, I'm pleased I have the bias bar pedal setup to account for these changes.

My front discs and pads are a week away from delivery and so although I have drawn the front caliper, after measuring the rear pad tonight I've made a fair few changes so I'll wait for pads before finalising front design.

A selection of spherical balls in one pic, and some machining I did today non TVR related on the 4th, cutting some cam profiles.

[portzi]

Engineer1949 has been doing a cerbera rebuild and has been an amazing read, but your work takes TVR reengineering to another level, amazing stuff.

[Poopdog]

Yes you will definitely need a bias for those monsters on the back,tbh the rear brakes don't do a great deal compared to the fronts but being four pot should be a more controlled pedal.
You thought about ABS system??