Pump My Ride - Ninety on air

[Turbocharger]

I think Arduino would suffice. There's an argument for doing this with discrete components, with some non-PWM solenoids it's just an OpAmp and some relays really.

It's chilly but sofa research has yielded some plug wiring diagrams, thanks to  http://paulp38a.com/range-rover-p38/how-eas-works/ for example:

 

[WesBrooks]

Is the STM32 more or less equivalent to Arduino Due? I was trying to get one of the Cortex M7 dev boards running to allow me to run a specific 3D Printer firmware with step-sticks to allow different drivers to be evaluated. Someone ended up donating a prototype board for the latest controller which has now diverted me off that for a while!

Not cheap mind but powerful for commonly available stuff:

https://www.mouser.co.uk/ProductDetail/Microchip-Technology/ATSAME70-XPLD?qs=sGAEpiMZZMv0WPLDnYsI73p1MuPOC8NtOVo4zscPU3UbR7%2FbF%2BfUTw%3D%3

 

But try with what you've got and fix whem it breaks or becomes limiting!

I'm watching this with interest as I was planning on resurrecting the RRC air system I have on the drive (sans bags). I was interested in changing to bags that can be upgraded I think the manufacturer was Arnotts. But that said since they canned RRC bags I guess they may do the same to P38 bags if they haven't already done so.

 

Edited March 31, 2020 by WesBrooks

[FridgeFreezer]

3 minutes ago, WesBrooks said:

Is the STM32 more or less equivalent to Arduino Due?

STM32 is a family, they go from ultra-low-power / low cost to high power stuff running a full RTOS.

F1xx and F4xx are mid-line with enough of everything for most projects and pretty cheap.

[WesBrooks]

RTOS has been running on the earlier version of the Atmel Sam Cortex M4 chips that I think were around 120MHz.

[WesBrooks]

That said Ed has mentioned thw STM32 Nucleo boards to me and It's on my list to check out along aide the super cheap tiny ESP boards.

Edit: The STM equivalent to the board I listed is the STMF7* range although that is slightly slower. But as originally said I don't think  it needs anything like that sort of punch.

Edited March 31, 2020 by WesBrooks

[Ed Poore]

Veering off topic here slightly but hopefully still relevant to the discussion.

I said above that Arduino stuff can run on the blue pill stuff but someone recently recommended to me Grbl as a CNC controller - had a look at their Github page and the second paragraph states "written in highly optimized C utilizing every clever feature of the AVR-chips to achieve precise timing and asynchronous operation". Which just screams to me they've picked the wrong platform to begin with . So although it's designed to run on an Arduino because of the developers I doubt it's a straight forward operation to run it on an STM32.

One of the huge benefits of the STM32 (although probably not in this scenario) is that it's an ARM core and well ARMs are ARMs and they're a heck of a lot of them out there. Provided you've written a decent hardware abstraction layer then if you've targetted one ARM then porting to a completely different hardware platform is fairly trivial. In my previous job we pretty much standardised on ARM or Intel processors and Xilinx FPGAs but it meant after (20+ years in the making) implementing a decent abstraction layer we could add new platform support in about an hour if it was based on an ARM processor and a higher-end Xilinx FPGA (the applications were too big for smaller ones so we're talking the £1.8k a pop chips here)...

[WesBrooks]

How do you get the P38 bags onto a RRC / Disco 1 (/ defender - don't think they are that different) style chassis? My RRC donor came with its airbags replaced with springs and I've not got close to a P38 chassis yet!

The Arnott Gen 3 bags offer longer travel in the off road mode and give a lower spring rate in off road heights. The latter I think will be quite important for me as the rebody on my kit will be lighter than the original, so the stock spring rate maybe on the firm side. I think that will be fine for road, but potentially jarring on a trail?

Edited April 1, 2020 by WesBrooks

[elbekko]

10 hours ago, Turbocharger said:

I think Arduino would suffice. There's an argument for doing this with discrete components, with some non-PWM solenoids it's just an OpAmp and some relays really.

It's chilly but sofa research has yielded some plug wiring diagrams, thanks to  http://paulp38a.com/range-rover-p38/how-eas-works/ for example:

 

It should all be in the P38 RAVE too

The extra wire in the compressor plug is the thermal cutout if I recall correctly.

[elbekko]

39 minutes ago, WesBrooks said:

How do you get the P38 bags onto a RRC / Disco 1 (/ defender - don't think they are that different) style chassis? My RRC donor came with its airbags replaced with springs and I've not got close to a P38 chassis yet!

The Arnott Gen 3 bags offer longer travel in the off road mode and give a lower spring rate in off road heights. The latter I think will be quite important for me as the rebody on my kit will be lighter than the original, so the stock spring rate maybe on the firm side. I think that will be fine for road, but potentially jarring on a trail?

The biggest problem will be front shock mounts, as you can't run a shock through the air bag. The RRC axles with air had a different shock mount I think.

[WesBrooks]

I was more concerned about RRC to P38 differences as I have the RRC that used to have air. That said if that's the biggest issue it is reassuring!

Edit: Arnott have responded saying they have no immediate plans to cease P38 airbag production.

 

Edited April 1, 2020 by WesBrooks

[Ed Poore]

@WesBrooks I'll take some photos of the front chassis bracketry sometime today as it's nice and visible. Rear less so unless I can pick the rear up.

[WesBrooks]

Thanks. I plan to strip off the RRC control gear to see what I have soon. I'll drop you another email soon regarding parts!

My fine electrickery design skills are slim to non existent but if the level sensors are simple pots, then the noise you'd get along the long lines goes some way to limit the speed of these systems? Some over voltage spike suppression needes on the lines too?

 

[Chicken Drumstick]

3 hours ago, WesBrooks said:

 

The Arnott Gen 3 bags offer longer travel in the off road mode and give a lower spring rate in off road heights. The latter I think will be quite important for me as the rebody on my kit will be lighter than the original, so the stock spring rate maybe on the firm side. I think that will be fine for road, but potentially jarring on a trail?

The stock air suspension on the p38 is actually quite a poor setup off road. Due to the long overhang at the rear you would want it in the extended ride height setting. But it was way to stiff and bouncy off road really. The Arnott Gen 3's should be a lot better, although the price of them is horrendous!

On the flip side, I often used to lock my p38 into the motorway/lowered setting. Because it genuinely rode a lot better than when in the Normal ride height mode, due to the softer springs. But you could also feel it was a lot softer in the corners too.

Really it was all the wrong way round. Low and firm for high speed is what I'd want. And a normal mode for general use that is comfy. With soft long travel suspension off road. ACE would also be the ultimate compliment on this era (any era??) of air sprung vehicle too. As you'd be able to keep a softer spring for ride quality, but still reduce body roll.

[elbekko]

1 hour ago, WesBrooks said:

I was more concerned about RRC to P38 differences as I have the RRC that used to have air. That said if that's the biggest issue it is reassuring!

Edit: Arnott have responded saying they have no immediate plans to cease P38 airbag production.

 

Ah sorry, my tired mind only responded to half the question.

No clue how different the bags are between the Classic and the P38...

[Turbocharger]

10 minutes ago, elbekko said:

Ah sorry, my tired mind only responded to half the question.

No clue how different the bags are between the Classic and the P38...

P38 bottom and certainly the top housing isn't compatible with a Defender chassis. I've got some RRC airbags on the way when I can collect (post-Corona) for more checking.

I *believe* the actual rubber bladder is the same diameter but a P38 (especially the rear) is longer.

I may yet try 3D-printing some top and bottom housings to take the longer P38 bags - that would provide an opportunity to shape the piston for spring rates at different heights, and add extra volume above the spring chair for a lower rate (or a large bore for a fitting for an additional switchable volume).

For now, let's see if the spring frequencies are even slightly close to coils and assess how it drives on P38 bags. 

[WesBrooks]

Yeah, I've heard not compatible a few times but that's from the bolt on, bolt off perspective. I've access to desktop 3D printers and have decent contacts in the commercial prototyping environment along side people with CNC equipment. That said I'm hoping it's solvable with salvaged brackets and plate metal work.

I'm not planning to go Arnotts straight off, but want an available upgrade path. I'll get the gear off the RRC soon. Once 'on the bench' its something I can stop and start around looking after my toddler son at the moment. Only vulnerability to that plan at the moment is he's cutting down on his daytime naps!

[Chicken Drumstick]

How do the LSE air springs attach? The pics look like they bolt on like the lower spring seat does on the coil springs:

 

P38 air springs have a socket and sit inside a mounting hole on the axle and are retained with pins. (ignore the fact it's a coil... the aluminium adapter is the same shape as the bottom of the p38 air springs)

 

 

[Ed Poore]

It's time to get very picture heavy...

Driver side spring and damper mount looking back towards the bulkhead. Spring location hopefully obvious, the top of the damper bolts through the bracket at the rear (just visible between the hard brake lines).

Same bracket but viewed from through the bulkhead towards the front of the vehicle. The damper sits inside the bracket with a bolt going through from the outer edge and into the threaded boss on the engine side of the mount.

Probably not that useful but looking from the wheel towards the spring mount (apologies for the finger in the corner ). The damper would sit down to the left (rear) of the spring mount from this view point.

Sideways view of the passenger side mount looking towards the engine bay (bulkhead is to the right):

And the axle bracketry (or rust in this case), sorry for the pile of carp on top but I couldn't be bothered to go and change my boots and find a pair of gloves to un-pile the carp.

You can see the bottom of the damper (the damper has actually been cut off above the bushes). The hole that the boss on the bottom of the air bag goes through is just visible behind the bushes. The hole to the right is actually an access / attachment hole I seem to remember for pulling / holding the clip that goes through the air bag in place. The two brackets poking upwards are for the front radius arms and the bump stop is to the right hand side.

[Chicken Drumstick]

RAC Parts do some front shock relocation bits that might work:

[WesBrooks]

I couldn't see them listed on their site. The RRC turret is bolted to the chassis just forward of the spring...

I think I'll be getting those turrets off, blasted and zinc plated when I can!

 

 

[WesBrooks]

...regards the LSE, excuse my ignorance but is that the long wheel base RRC? Would that have a heavier spring to cover for potential extra payload, or lower because the weight distribution may be alittle lighter over the rear axle?

[Turbocharger]

LSE and standard RRC have the same spring part number, I believe. The difference would probably have been made up by a slightly higher pressure by the time the levelling process had done its work.

Great P38 pics Ed, thanks. At the moment I've wedged some bits of wood in the gaps to trial-fit the springs while I assess the frequencies. They're wrong, but not so wrong they wouldn't work with an adaptor piece top and bottom.

Disco 2 rear airbags are still an option for one/both ends - different fittings turned up and (bad news) they're not standard M8 but (good news) not so far away so they'll screw in far enough for an O-ring to seal before it all goes horribly tight.

The fitting it really needs (top of pic below) is 7.7mm OD across the male threads and 0.75mm pitch or some dark hex fraction of an inch equiv. Could be M8 fine pitch? (The bottom one is today's M8 Amazon delivery).

[Turbocharger]

3 hours ago, Chicken Drumstick said:

RAC Parts do some front shock relocation bits that might work

Paddock do (well, did - no online shop 😷) the relocation kit I got to put the shock in that forward position, it's galv but not the highest quality. It'll do for now.

[Ed Poore]

1 hour ago, Turbocharger said:

Great P38 pics Ed, thanks.

If it's of any use I could get out Mr. Hot (plasma cutter) and/or Mr. Angry (9" grinder) and cut out the chassis sections. Wes wanted them anyway - I've got a Inventor installed on my PC in the office so could probably knock together a 3D model of the chassis end of the setup if people are interested?

Probably shouldn't do it for a couple of weeks though because I've got to try and get the top floor flat ready for a vet who's coming to stay and always have work in the background.

[WesBrooks]

What are the rough figures for the usual draw for the compressor and solenoids? Curious to see if I could get it running from the bench on a 350W or 500W PSU. I would check, but the two spare 12V batteries I've got are goosed.