For Questions Regarding WOFs/CERTs/NUMBER PLATEs

[NickJ]

Looking to do a pop top camper conversion on our Defender, running through the threshold doc, a cert is required, no argument there but i'm struggling to find any information on what design requirements exist for camper conversions. 

When we priced up existing production conversions, the price well and truely pays my time and the purchase of tools so thats the road we're looking to follow, i've allready completed the bulk of the CAD modeling but its now into details, will calculation sets be asked for? if so, what is the certifier wanting to see, i'm hoping its just pragmatic proof its no worse than factory?

Pretty keen to go knock on the local certifier's door with a reasonably well detailed set of plans for the first chat so that I can complete the design and get onto the fun stuff.

 

 

[shizzl]

Took the ute through cert couple of weeks ago, got a fairly minor list to sort.

sorted them all.

took it back in yesterday, and now been told that my lower arms won’t pass.

 

according to the certifier, they received a memo last week stating lower arms can no longer be compliant that were coil, shock set up and changed to a qa1 style Coilover design. Bottom arm is a stamped double skin type both captive nuts on top, with the trunion mounted below the arm. 

 

great to find out after blowing $300 on trailer hire, fuel and rucs. 
 

so, the question is now, what kind of cost is getting lower arms NDT tested and a report?

he doesn’t know what is needed to rectify this issue yet but will call lvvta tomorrow. Just wanting to plan ahead I guess.

 

i may need to weld a plate in below the control arm and have the shock mounted above the plate (opposite to factory). 
this will then require NDT report I guess.

 

[RXFORD]

If it were me, I would find out if removing the oem captive threads, then swapping the mounting bar to the top side of the lower arm would be fine. That way the compression load is on the arm and not solely relying on the tensile strength of fasteners.

 

Also, our resident certifier Clint has customers in the Puke area, as does his boss Mark whos workshop is located there. There is a certain irony about asking for free advise on this site, then not supporting the guy who answers our questions, and then moaning about the situation with the certifier you did use...

 

[shizzl]

 

 

the issue I have is the constant rule changes with very little clarity on it. 
 

certifier can’t confirm if it was factory lower arms or aftermarket lower arms that failed.
 

Hey, I’d happily use Clint if our schedules aligned for that to happen, which is why I don’t pester him with questions.

i ask the collective, if he answers the question then bonus. 

[JustHarry]

On 26/11/2025 at 21:51, NickJ said:

Looking to do a pop top camper conversion on our Defender, running through the threshold doc, a cert is required, no argument there but i'm struggling to find any information on what design requirements exist for camper conversions. 

When we priced up existing production conversions, the price well and truely pays my time and the purchase of tools so thats the road we're looking to follow, i've allready completed the bulk of the CAD modeling but its now into details, will calculation sets be asked for? if so, what is the certifier wanting to see, i'm hoping its just pragmatic proof its no worse than factory?

Pretty keen to go knock on the local certifier's door with a reasonably well detailed set of plans for the first chat so that I can complete the design and get onto the fun stuff.

 

 

Who are you going to use.

That's probably something Jon palmer would be a good bet for.

He comes up to chch once a month or so 

We use him for all the scratch builds at work 

 

[NickJ]

6 hours ago, JustHarry said:

Who are you going to use.

That's probably something Jon palmer would be a good bet for.

He comes up to chch once a month or so 

We use him for all the scratch builds at work 

 

Haven't made any decisions on who yet, is that who you would go with for this?

Just want to tidy up the design a bit further then approach a certifier, its a bit chicken and egg but i'm keen for them to see a reasonably solid design so that there is a clear direction to go, don't want to mess them about or have to rebuild.

Going to be a pretty big project over the coming winter providing the cert process doesn't throw any curve balls.

[smokin'joe]

does changing transfer cases from vicous coupling full-time 4WD to split ratio selectable 4WD stay inside WOF, as long as i don't cut holes for transfer cable ?
 

[Bearded Baldy]

Like an 80 series part time conversion? No drama for wof as main suspension and driveline/shafts are the same.

[HumberSS]

What's the deal with captive nuts for things like gearbox cross members etc? Do you need to use a high tensile captive nut to match the bolt, and if so any sources? Ideally weldable but I guess this changes tensile??  I'm thinking of specific parts of my camper build, and how stink nuts and bolts are, and how what I have done is possibly not quite on the money. TIA

[RXFORD]

6 hours ago, HumberSS said:

What's the deal with captive nuts for things like gearbox cross members etc? Do you need to use a high tensile captive nut to match the bolt, and if so any sources? Ideally weldable but I guess this changes tensile??  I'm thinking of specific parts of my camper build, and how stink nuts and bolts are, and how what I have done is possibly not quite on the money. TIA

Captive as in a 'cage' style that floats or threaded boss welded to a plate?

If its welded, or you want it weldable, then should be a 'mild' tensile. Anything over 5.5 is starting to get into the medium and 8.8 is high so shouldn't be welded unless you have a suitable proceedure.

I have a customer ute here that has had 8.8 bolts welded to lower arms by original shop that built it for front shock mounts. They will need cutting off and something more suitable welded on.

Things you are more likely to get pulled up on would be thread engagement. I generally try to use the minimum 1.5x bolt diam rule for engagement on captive threaded boss'. And also correct shank lengths so loading isn't on threads. This is more for critical stuff though. 

What have you done that you are worried about?

 

[HumberSS]

1 hour ago, RXFORD said:

Captive as in a 'cage' style that floats or threaded boss welded to a plate?

If its welded, or you want it weldable, then should be a 'mild' tensile. Anything over 5.5 is starting to get into the medium and 8.8 is high so shouldn't be welded unless you have a suitable proceedure.

I have a customer ute here that has had 8.8 bolts welded to lower arms by original shop that built it for front shock mounts. They will need cutting off and something more suitable welded on.

Things you are more likely to get pulled up on would be thread engagement. I generally try to use the minimum 1.5x bolt diam rule for engagement on captive threaded boss'. And also correct shank lengths so loading isn't on threads. This is more for critical stuff though. 

What have you done that you are worried about?

 

Thanks man, basically I have an upper gearbox cross member that is slung off the chassis, which the lower gearbox cross member bolts up to from below. Presently I have nuts welded on top of plates on the upper cross member and then the lower member which supports the gbox bolts up to it from below. The nuts are just some ZP nuts I had lying about which are tacked on the upper side of the plate if that makes sense. There are 4 x M8 per side from memory. 

[dmulally]

26 minutes ago, HumberSS said:

Thanks man, basically I have an upper gearbox cross member that is slung off the chassis, which the lower gearbox cross member bolts up to from below. Presently I have nuts welded on top of plates on the upper cross member and then the lower member which supports the gbox bolts up to it from below. The nuts are just some ZP nuts I had lying about which are tacked on the upper side of the plate if that makes sense. There are 4 x M8 per side from memory. 

FWIW I had some welded nuts in the imp for a doubler plate through the chassis rail and I got a few questions about the doubler plate dimensions and being rounded off on the chassis side but nothing on the nut. They were 7/16" nuts. 

[RXFORD]

38 minutes ago, HumberSS said:

Thanks man, basically I have an upper gearbox cross member that is slung off the chassis, which the lower gearbox cross member bolts up to from below. Presently I have nuts welded on top of plates on the upper cross member and then the lower member which supports the gbox bolts up to it from below. The nuts are just some ZP nuts I had lying about which are tacked on the upper side of the plate if that makes sense. There are 4 x M8 per side from memory. 

Being that its non-critical and there is 4 per side I would be surprised if you got pulled up on them. Tacked on vs fully welded is better too.  It doesn't really say anything in the book about that sorta thing specifically, other than the fasteners being a suitable size and grade for the application, which could be interpreted differentely depending on certifier.

@cletus might have to offer his opinion on this one.

 

[smokin'joe]

On 06/12/2025 at 07:18, Bearded Baldy said:

Like an 80 series part time conversion? No drama for wof as main suspension and driveline/shafts are the same.

similar, have both part-time and full-time 80's
full-time 4wd hiace....... pain in the arse not being able select 2wd, and be cool to add low ratio if needed/available

 

[Bearded Baldy]

Look on the VIRM.

Table 13.1.1

 

 

 

 

 

 

 

 

 

P.s. not that i, as an inspector would ever suggest it, it eye appeal is 99% of it, make it look legit. 

 

[Bearded Baldy]

I personally wouldn't have an issue with it, keep driveshafts the same, fit freewheeling hubs to the front etc etc. If you are only changing the case itself and the mounts all fit the same, i would allow a hole cut in the floor for a cable and mount.

But it would have to look good.

Turn up with something from the wall of shame and things will go downhill fast.

[smokin'joe]

On 10/12/2025 at 20:01, Bearded Baldy said:

I personally wouldn't have an issue with it, keep driveshafts the same, fit freewheeling hubs to the front etc etc. If you are only changing the case itself and the mounts all fit the same, i would allow a hole cut in the floor for a cable and mount.

But it would have to look good.

Turn up with something from the wall of shame and things will go downhill fast.

there are auto versions with 2/h/l transher............ am sure if it was from super custom, it would have gorgeous brown velour trim to match my grey vinyl 

[Bearded Baldy]

Ok. So the factory ba/bf falcon rear seats use this boomerang shaped bracket to hold the center of the back seat up.

I need to make another bracket, and i plan on putting it through the black layer, so long as there is nothing in behind it that will stop me fitting a doubler plate. 

Which brings me to my question.

Reading the rulebook my understanding is i can use a piece of 6mm plate, 150mmx50 with 2 10mm threaded holes for the seatbracket to bolt to, and 5mm threaded holes to secure it to the floor with bolts and spring/flat washers.

Like this.

 

Does that make sense? Workable idea? I know i could use 3mm plate and rivets, I just dont like rivets. Also unsure if i can use one plate for 2 bolts?

Tell me if i am being stupid.

Oh, they are unstressed seats.

 

[cletus]

Doubler plates must be 3mm according to the rule book 

2 bolts on one plate that size will be ok as the minimum is 3000 square mm per Anchorage 

[Bearded Baldy]

Thanks @cletus, i read it as 3mm being the minimum, good thing i asked. 

Which means the whole idea is goosed right? Unless i was to weld some captive nuts on?

I may be really overthinking this.