[Scotty274]

So I was asked the other day to help convert an old HQ Holden, Ute because "Dude you know something about electric cars building that there Jumbuck and you want to start a business one day"

Owner wants a complete Tesla performance rear drive unit (Cool, that will be fun) and a complete Tesla pack (likely out of a model S)

He's scouring the Auctions in the hopes of getting a complete car that's been written off. So I'll likely have a fair chunk of time, as in 18 months of having alerts turned on, I haven't seen any Tesla's go to Auctions. Let alone a Performance one.

Anyway, on to my question:

I have looked at the chassis and a 1970's Chassis is not really build to have a bucketload of torque twisting the rear of the chassis (CAD already says I have around 80% of the strength I need to make the rear end work. Or a 0.8% safety factor, either way, the rear end buckles.

As for the battery, would be nice if I could sit it under the cab and bolt the cab to/near the battery, however the chassis rails are too narrow in that section by around 2" each side to accommodate a full battery, oh so so close it's painful. Literally a rail width wide I'm being foiled by, as that would be the neatest solution.

So I emailed QLD Department of Transport and Main Roads and asked the question about modifying/replacing the chassis, I was told:

1. I can leave a "Significant Member" of the chassis in place and functional and it's not a "New" chassis
2. I can replace the chassis incrementally over time, and it's incrementally repaired, but it was never actually replaced (Chassis of Theseus)
3. I can build a whole new chassis to accommodate Power Steering, ABS Brakes, Independent Suspension All Round, etc and I will need to meet 2021 requirements for registering a CAR (As it isn't an ICV due to it using a "Substantial Body Component from a manufactured car")

So I get option 1, I could leave the entire cab mounting section as a Significant Member and have that as-is, and then build an area up the front as a Froot, maybe stretch the wheelbase a tad to fit the whole battery behind the Cab, that would be rather cool, and then weld the whole lot together with a 50 year old piece of chassis in the middle.

It's option 2 that confuses me, as when they rang me to see if my issue had been resolved satisfactorily, they ended up putting me through to technical standards, and I had a good chat with them.

I asked how do they verify that the chassis was replaced incrementally, and he said "Oh, photo's, weld lines where they shouldn't be, that kind of thing"

I asked if there is any point during my build where they inspect it, and verify that I am incrementally fixing it?

They said there is not.

I asked then "So if I replace the rear body section in entirety, that's cool?"

Yes it is....

If I then replace the front section, that's cool too?

Apparently it is.

Then if I replace the Cab Mounting Section in the middle, because I encounter an issue....that's also cool...

Anyone encountered this?

It just seems a bit too easy that I just weld each new piece on, then cut the next old piece off, and then weld the new piece on, and then cut the last piece off and weld the new piece on...and take photo's along the way....

 

[brian_]

That's hilarious!

For those - like me - who don't know one Holden from the next: Holden Statesman (HQ)

 

[Scotty274]

That's hilarious!

For those - like me - who don't know one Holden from the next: Holden Statesman (HQ)

More specifically, this is a One-Tonner Ute Version

 

[brian_]

After a bit of searching, it appears that these Holdens had a structural design which was common for GM at the time (1960's-1970's): they have a separate frame forward of the firewall, unibody construction from the firewall back, and the tail ends of the front frame extend under the body to splice the two together. This was used in North America on the X-Body, F-Body, etc. This illustration from a Holden advertisement confirms the arrangement:

... and this listing for a used part shows an example:

So with that background, now the relevant part...
Some utes have a cargo box which is integrated with the unibody (eg. this HQ Belmont ute), essentially being the station wagon with the roof missing. This variant of Holden (which matches an HJ One Tonner) has a separate tray body. That means that either

1. the unibody of the cab section extends as frame rails under the tray, like a modern Mercedes Sprinter or Ford Transit chassis-cab, or
2. there is another separate frame section at the rear, like the one at the front, bolted to the unibody in the middle, carrying the rear suspension, and supporting the tray, or
3. in this ute (only) the "front" frame is actually a full frame, continuing to the rear, as shown and called a "full length chassis" in this one-tonner advertisement (image below) or
4. something else that hasn't occurred to me.

Another old Holden ad shows structural elements that suggest #2, a rear frame section. It refers to the design as a "stub frame chassis". In this illustration, it looks like the rear "stub frame" might even overlap the front section, with the unibody essentially as a splint to splice the two frame sections together. On the other hand, while reading too much into an advertising illustration is never good, it does look like only the front has bolted connections to the unibody, and the rear "frame" section might just be highlighting of the rails within the unibody structure.

So, what's under your ute, and is it different from other (presumably lighter-duty) Holden utes of the era?

 

[Scotty274]

Option 3, the tonners are a full frame setup

 

[brian_]

Option 3, the tonners are a full frame setup

Thanks
In the end, these vehicles are the same as any traditional pickup truck, but with a low cab styled like a passenger car.

So the cab is almost irrelevant, except that in the Chassis of Theseus approach, each of the ephemeral intermediate stages needs to support the cab to be plausibly functional.

 

[brian_]

If I understand this correctly, the intention is to put a Tesla drive unit at the rear, with (Tesla or otherwise) independent suspension.

It just seems a bit too easy that I just weld each new piece on, then cut the next old piece off, and then weld the new piece on, and then cut the last piece off and weld the new piece on...and take photo's along the way....

A challenge is that if you space the new frame rails further apart (which I assume is a major purpose of the modification) they don't work with the remaining not-yet-"repaired" section. I suppose if you make the break between sections just ahead of the rear drive unit, you could have the original spacing there, with the (wider) forward section and (IRS) rear section being done one at a time. It might be hard to explain how this is incremental work if the intermediate stage is not functional, so perhaps do the rear first with a small temporary battery setup on the cargo tray or in the fuel tank space. It would also be difficult to define one cut line through the frame which would be far enough forward to accommodate the drive unit and yet far enough back to be entirely behind the battery.

I have no idea if this would actually be approved there... or even here.