Nottm_S2

Ouch
Motorsport is dangerous eh
Saw the Nomad at the bike show today. Still like for road twattery but the options list is funny. They had an old one, hardly any use, 70k as you said

BuggyofMildDiscomfort

Yep, been on scene to a few, had to tow one of the cars home after for inspection too, not easy. Tree's don't move much even if you're only at 30mph, and cross ruts or flips can break a spine. But, if you're gonna go, go doing something you love.

BuggyofMildDiscomfort

Or the bit where you hit a bump on track and nearly go down a little cliff:

Nottm_S2

Noone lives forever

I bet his bum was fairly tense in the last few seconds there
I mean to say on Nomad, it started at 28k + vat but not sure that was road worthy

BuggyofMildDiscomfort

Oh he was stuck there on the brake pedal for like 10-15 minutes while they got a tow car up behind him, wasn't good when he's screaming 'cause his leg was going numb!

Yea there's something like a 2-3year wait list on a new one though?

martin j

Yep, adrenaline is brown, and appears in yer trousers.

BuggyofMildDiscomfort

First race is only 2 days away guys, look, we're all ready and set to go, perfect!

[thumb]https://i.imgur.com/rAs4Ujd.jpg[/thumb]

Oh. Errr. Maybe some bits to finish off.
I've been rather busy and left Ed to his own devices so he's basically rebuilt half the cockpit, controls and bulkheads to get the new seats in. Note to self, slightly bigger seats don't always fit no matter how close they look, or how much you go "Ah it'll go in!"

To that extent the front suspension is going back on as it is without the new uprights, there was far too much work in the rest of the car to fit that and set it up too -he's made some new arms which are plated to reduce the stress on the outboard weld:

[thumb]https://i.imgur.com/e9rYhB6.jpg[/thumb]

They're a touch wider too to spread the weld over more area. And we have our spare set to take with us this time....

I've done some shimming on the rear uprights to adjust the rear camber and give me more range to adjust towards toe-out on the rose joints, and split the rear dampers to start some work.
Pretty much deliberately trying to make the car more tail happy to quell the mid corner understeer, if it gets a little too much we can go back up on the front arb size a bit to tame it.

Okay, so a few issues with fitting the new Motodrive seats - one, they have a little more lean angle on than the old seats, that's a good thing for stopping your ass getting sore while bouncing along rough terrain, because it spreads the load more over your thighs and back - and they also have wider shoulders and some side impact padding for the helmets, also a good thing if your head is bouncing around, but... that's a bad thing if you're trying to fit it in a tiny cabin that was basically built around some smaller framed Corbeau's.

So the seat bases needed moving forwards, quite a bit, and the seats are a bit taller as they have a few inches more padding in the base and they're a stronger/safer seat overall, which means tilting them and shuffling forwards a little more just to make sure there's plenty of roof clearance.

By this point, your knees are on the dashboard, or your feet are through the bulkhead, and as I quite like my feet and really don't fancy extreme weight saving measures like taking my legs off below the kneecaps, some drastic surgery to the car comes in....



Firstly, the co-drivers footrest (and windscreen washer tank), gets pushed forwards and now becomes part of the bulkhead itself:



Along with modifications to the bulkhead and pushing forwards the battery tray too.

And then the next trick is the drivers side, now here the pedals were right up against the bulkhead anyway, pushing them forward then required cutting and folding a few bulkhead that is a few inches further back, pushing the fuel tank and brake reservoirs forwards slightly so the hoses all reach the master cylinders - which are also getting pushed forwards a few inches (along with the pedals themselves) on an adaptor plate:



Continuing on with "PhillipM's First Law of Exponentially Cascading Knock On Effects From Changing One Simple Thing", that also then meant remounting the foot rest plate further forwards, and then the throttle cable was no longer long enough so that had to have an extender made for it too, along with remounting the brake sensor switch. Fun times. And the seats aren't in yet.



Onto the next bit - remember I just mentioned about the seats being taller backed and the base foam being thicker? Both great things, but with a caveat. That means the seats need to be lower, as it's a short cab and your head would be far too close to hitting a rollbar tube otherwise.
And because we've just pushed the seats forwards, they hit that diagonal T45 tube we put under the old seats a year or two ago to give some rock protection...so angle grinder back out, and cut out that bar, lower the seats as far possible while still leaving a touch of clearance under them to the floor armour just in case...and then we had to forgo the nice diagonal protection tube (which also stiffened the floorpan) and pop two tubes at angles as close as we could to the seat bases instead, front and back.
Now this might seem a little silly but we've landed on big 1ft diameter stones and rocks before and twice they've punched a hole clean through the floor armour, so this is a little extra weight for peace of mind/protection.



So now there's bars either side of your bum. Just in case. And some little stiffeners just so we don't loose the chassis stiffness benefits that the old bar gave.

I didn't take a picture but as you might guess from the cover being off in front of the gearbox, the gearlinkage has had to be remade and the gearlever shifted left an inch to clear the wider wings of the new seats too, along with 4 new seat mounting frames being made and the harness clip on points being moved to suit.

Don't believe your brain when it goes "They're not that much bigger, we'll get those in, easy"

So yes, a whole lot of time disappeared just to get comfier. But I think it'll be worth it those Motodrive seats were custom fitted/shaped for us and they're so, so much better to sit in.

Next step, well these dampers seemed far too shiny and lovely not to vandalise so onwards:



...but not before getting the seats in to go 'ooooh' at:





As for the revalving, well yes, that was fun - one of the dampers it turns out didn't have the backup washer the correct way around/torqued enough and caused a little wear - nothing on the important bits but you can see the debris on the ally bearing spacer here:



And it also looks like the bleed shims (the big shims on the left with the cutouts) were oriented wrongly - where you'd assume the tabs line up with the little raised bits on the piston, they were 45* rotated on that damper, which then leads to some odd effects as the initial compression pressure acts on the shim stacks behind those and the bleed shims themselves only start to lift in the high speed area.
Unfortunately, I've never been in these dampers before and Fox never used to run bleed shims (they ran holes in the piston for it instead - finally they've moved to the same system you see on most high end stuff with Ohlins/Penske/Reiger to make it easy to change bleed amounts) - so after spotting that I just assumed it was deliberate to soften initial response, and kept things that way around when I rebuilt it.
It was only when I opened the last damper that had the shims the way around I originally expected - and no wear, I realised I should have assembled those bleed shims as I originally intended!

Anyway just for this race I've put the bleed shims back together the way the initial one was setup, and then I'll turn them around for the next race after re-running some fluid sims - I just simply don't have time to correct it right now, and I wasn't expecting basically brand new dampers to be mis-assembled. Should have trusted my instincts there.

I have made quite a change though, there's much less low speed bleed now so that I don't have to rely on running the adjusters on max (that causes issues with sensitivity and the pressure balance inside the dampers).
The flutter stack is massively reduced on the compression side, which is referring to the small shims backing up the large washers on the bottom in the middle there - basically that makes a 2 stage stack so the low/mid speed damping is reduced a lot and the high speed is very stiff. That's fine for the UTV these were coming off where they need to get it suitable for everyone from comfy road use to people hammering them over dunes, but it's also softening the damping right where a race car like this needs it - jump landings, bottoming out from elevation changes, washboard stuff where it's dug out in the mud, etc.
It's almost the same for the rebound side (the top shims) - they've used a flutter stack to give the rebound adjuster more range and with a soft initial stack and then a stiffer high speed stack they can cope with a wide range of spring rates owners are likely to throw at a UTV, basically running a progressive damping curve but with the option to add a lot of low speed rebound control.

That unfortunately for us with quite a lot of spring preload and weight at the rear means that the damping is reduced right where it's controlling the rear kicking up over rolling jumps, as you can see on some of the jump pictures it lands nose heavy a lot of times if it's a steep take off.
The only way to really tame that was to wind the rebound adjuster to almost full hard (it adjusts the low speed mainly but also the mid speed damping somewhat) - but because that also winds up the low speed damping which is mainly body control and handling related, that would make the car very nervous and skitterish on the brakes or the way into a corner so I couldn't go too far.

Given we also don't need that range of adjustment I've pulled that stack completely and now it runs a more conventional tapered stack that gives slightly digressive rebound damping, that means we have a lot more midrange damping, and I can just use the adjuster for what it was designed for - tailoring the handling responses of the car rather than trying to patch up problems in the main valve stack.

I've left the high-speed damping somewhat similar at the moment just for reference but I suspect I'll end up reducing that somewhat anyway, we have quite a lot of unsprung weight, and our tyres are both quite a lot larger and run lower pressures than an UTV - so I think a softer setup there will benefit us more in terms of getting the tyre back in contact with the road sooner vs the sudden increase in contact patch pressure that might cause.

One for another time

Anyway, after all that rambling they're back together and re-gassed.



I also swapped the oil to some low-friction oil - the stock Fox red oil isn't too bad but it has some really bad issues with stiction I've noticed over the years - especially in dampers this size, not so much of an issue in smaller stuff, whereas the stuff I'm using now has some really fancy additive package to reduce friction and wear at the expense of needing changing a little more often.

...while I'm rambling about dampers I wasn't impressed by the pistons either - they're very low flow so they choke the valving on impacts and they have a lot of sharp edge entries into the ports too. I'll be swapping those out for either some higher flow alternatives when I can get hold of some (Fox sell them for racers in the US), or making a pair.

Just trying to get the thing back together the first race is this weekend and it needs to be entered by tommorow

Slight issue in that the clutch slave cylinder is leaking so that was a fast fix tonight to get it back on it's wheels after leaving it like this trying to get a new cylinder shipped asap!



And finally back on it's wheels:

chrispayze

Interesting stuff about the dampers. I'm an engineer and a mountain biker, so at least some of it made sense!

BuggyofMildDiscomfort

Valving is rather interesting. So long as you count like 20 hours of math work and simulations before even changing anything as interesting.

martin j

What gas do you use in the shocks? Please just say oxygen, that’d be boring and obvious, it’s needs to be something exotic.