Shart Speedstar: Track Day Silliness
Discussion
So my father was getting rid of this:
a very ropey Smart Roadster with engine woes and generally in a sorry state, and in a weaker moment I decide to turn it in to a track day project. I'm aiming to make it as quick as I can by making it as light as I can, and as cheaply as I can. And I do mean cheaply. The engine is shagged and the gearboxes don't suit track days so a bike engine it is. I've not decided which one yet but probably a gen 1 Hayabusa. There's a bit of work needed before we get to that though, so here comes what's been christened the Shart Speedster...
Looking at it, it's a targa and the windscreen seems to add very little to torsional rigidity, so a very quick check on headroom:
and after some sparks and loud noises it becomes a speedster:
Excellent. No glass, bin the wipers and wiper motor and washer bottle, much lightness, and there's a touch of Lotus 3-Eleven/McLaren Elva vibes going on. If you're drunk and squint at it. I need to add strength in, so the doors are scrapped in favour of door bars, which the plastic door skin will bolt to. More triangulation will naturally be added here later, along with a roll hoop:
The servo is junked for a single master cylinder. Yes I know this isn't ideal but remember: light and cheap. I've never heard of these failing (had bother with one where the domed retaining washer was fitted backwards, that was no fun to diagnose) so I'm risking having only the one. Please don't judge me:
There's a bias valve to be fitted to the rear, installed under the bonnet in case anyone decides it'd be funny to move the lever when it's parked up. I've struck a questionable brainwave with the back brakes (of which more later) so this layout will change slightly:
The throttle pedal is fly by wire so no use really, so making a quick jig:
I made up a pedal using the existing bracket, and a relatively simple cable should do the trick from here.
Hope you enjoy this for what it is, more updates and lots more questionable decisions to follow, hopefully soon as I have good help on this one, my three year old lad is giving a hand....
a very ropey Smart Roadster with engine woes and generally in a sorry state, and in a weaker moment I decide to turn it in to a track day project. I'm aiming to make it as quick as I can by making it as light as I can, and as cheaply as I can. And I do mean cheaply. The engine is shagged and the gearboxes don't suit track days so a bike engine it is. I've not decided which one yet but probably a gen 1 Hayabusa. There's a bit of work needed before we get to that though, so here comes what's been christened the Shart Speedster...
Looking at it, it's a targa and the windscreen seems to add very little to torsional rigidity, so a very quick check on headroom:
and after some sparks and loud noises it becomes a speedster:
Excellent. No glass, bin the wipers and wiper motor and washer bottle, much lightness, and there's a touch of Lotus 3-Eleven/McLaren Elva vibes going on. If you're drunk and squint at it. I need to add strength in, so the doors are scrapped in favour of door bars, which the plastic door skin will bolt to. More triangulation will naturally be added here later, along with a roll hoop:
The servo is junked for a single master cylinder. Yes I know this isn't ideal but remember: light and cheap. I've never heard of these failing (had bother with one where the domed retaining washer was fitted backwards, that was no fun to diagnose) so I'm risking having only the one. Please don't judge me:
There's a bias valve to be fitted to the rear, installed under the bonnet in case anyone decides it'd be funny to move the lever when it's parked up. I've struck a questionable brainwave with the back brakes (of which more later) so this layout will change slightly:
The throttle pedal is fly by wire so no use really, so making a quick jig:
I made up a pedal using the existing bracket, and a relatively simple cable should do the trick from here.
Hope you enjoy this for what it is, more updates and lots more questionable decisions to follow, hopefully soon as I have good help on this one, my three year old lad is giving a hand....
Excellent, very interesting plans. My understanding is that Smarts are fairly strongly built. Are the new door arrangements intended to add impact protection, cut weight, or add torsional rigidity?
It sounds like you know what you're doing, so looking forward to seeing this out on track!
Have you seen the Japanese equivalent? https://www.pistonheads.com/gassing/topic.asp?h=0&...
samoht said:
Excellent, very interesting plans. My understanding is that Smarts are fairly strongly built. Are the new door arrangements intended to add impact protection, cut weight, or add torsional rigidity?
It sounds like you know what you're doing, so looking forward to seeing this out on track!
Have you seen the Japanese equivalent? https://www.pistonheads.com/gassing/topic.asp?h=0&...
All of the above with the door bars. The doors are aluminium framed, surprisingly quite heavy but well designed and safe in the road car. It’s side impact first with more bars to comes, then torsional, then weight really. It sounds like you know what you're doing, so looking forward to seeing this out on track!
Have you seen the Japanese equivalent? https://www.pistonheads.com/gassing/topic.asp?h=0&...
And I love that Beat, great fun!
This has the potential to be very awesome!
Looking at the side profile after you'd binned the windscreen, it actually looks like it was meant to be a speedster - or at least I can easily imagine it looking so. A couple of flying buttresses at the back would really work, I reckon. Although, that might not be true to the "cheap" ethos...
Some aesthetic inspiration?
Edit: Sorry, I've just noticed that you've already drawn the 3-Eleven parallel.
Looking at the side profile after you'd binned the windscreen, it actually looks like it was meant to be a speedster - or at least I can easily imagine it looking so. A couple of flying buttresses at the back would really work, I reckon. Although, that might not be true to the "cheap" ethos...
Some aesthetic inspiration?
Edit: Sorry, I've just noticed that you've already drawn the 3-Eleven parallel.
Edited by TheJimi on Tuesday 2nd August 01:56
I like this a lot. Always thought the Smart Roadster with the little rear glass bit was a good looking little car just utterly ruined by the gearbox.
Really looking forward to how this turns out, you look to have the skills necessary to make this a really interesting project to follow
Really looking forward to how this turns out, you look to have the skills necessary to make this a really interesting project to follow
TheJimi said:
This has the potential to be very awesome!
Looking at the side profile after you'd binned the windscreen, it actually looks like it was meant to be a speedster - or at least I can easily imagine it looking so. A couple of flying buttresses at the back would really work, I reckon. Although, that might not be true to the "cheap" ethos...
Some aesthetic inspiration?
Edit: Sorry, I've just noticed that you've already drawn the 3-Eleven parallel.
I totally agree, I think the shape needs buttresses to look right. Luckily it's the Coupe version so it has the side window panels on the rear and I'm hoping these will look OK. The plan is to run these panels with no bootlid, and I'll cover the insides with some new panels to clean up the aero a bit.Looking at the side profile after you'd binned the windscreen, it actually looks like it was meant to be a speedster - or at least I can easily imagine it looking so. A couple of flying buttresses at the back would really work, I reckon. Although, that might not be true to the "cheap" ethos...
Some aesthetic inspiration?
Edit: Sorry, I've just noticed that you've already drawn the 3-Eleven parallel.
Edited by TheJimi on Tuesday 2nd August 01:56
Got a cheap and cheerful steering wheel with a removable boss, and machined the boss to fit over the standard splines. I plan on getting someone who can weld better than I can to weld this up for me! The plan is to slot the boss so that the weld isn't just circular around the column but travels up along the boss too
pthelazyjourno said:
With metal surrounds and glass rear window, Coupe is supposed to be around 20kg heavier than the notchback - may be worth getting the angle grinder out again and getting rid of the rear windows, you could probably pick up a boot lid for £20ish if lightness and cheap is the aim.
That’s true, but I think most of the 20kg is in the glass bootlid which I’m not using, and I way prefer the profile with the plastic side windows. I’ll wait until I have an engine sitting in it and see what height it is and what way I’ll work the air inlet and go from there. The more I work on the Smart the more impressed I am by it. And frustrated. It had so much potential and has so many nice touches but they really made it needlessly complicated, like they were trying to be too clever by half. If they had kept it simpler with more of an MX-5 ethos I think it's generally accepted that it could have been a huge success. Like did the tiny 3 cylinder engine really need 6 spark plugs when 3 of them are basically inaccessible? And of course there's the infamous gearbox:
A fully automated manual, with a three speed sequential cluster and with two final drives, giving six speeds. They really went to an awful lot of work to end up with a less than ideal solution. Anyway, there's a motorbike engine and gearbox going in this so I'm keeping the diff and driveshafts and the rest is going to end up where I'd suggest it should have been put originally (a skip). Firstly I removed the engine subframe:
Then made a jig to locate the diff, using cups under the driveshafts:
And, using an amount of mechanical butchering I'm not very proud of, removed the diff:
And putting it back in the car:
Now I wait to get the bike engine sorted and dropped in there, to figure out the best way to mount the diff. But looking at the two final drives on the diff got me thinking, how about a sprocket to replace one gear and a single brake disc to replace the other? I've nothing against the rear drums but they would need reconditioning, and the car will only be half the weight it was, surely one disc would work?! And if I used one motorbike front brake disc and caliper imagine how light and cool that would look?! I'm not sure yet, maybe one car type disc and caliper would give a more suitable rear brake force, but I've cut up the drum back plates now anyway so I'm committed to something along these lines, and it'll be interesting to see what works.
A fully automated manual, with a three speed sequential cluster and with two final drives, giving six speeds. They really went to an awful lot of work to end up with a less than ideal solution. Anyway, there's a motorbike engine and gearbox going in this so I'm keeping the diff and driveshafts and the rest is going to end up where I'd suggest it should have been put originally (a skip). Firstly I removed the engine subframe:
Then made a jig to locate the diff, using cups under the driveshafts:
And, using an amount of mechanical butchering I'm not very proud of, removed the diff:
And putting it back in the car:
Now I wait to get the bike engine sorted and dropped in there, to figure out the best way to mount the diff. But looking at the two final drives on the diff got me thinking, how about a sprocket to replace one gear and a single brake disc to replace the other? I've nothing against the rear drums but they would need reconditioning, and the car will only be half the weight it was, surely one disc would work?! And if I used one motorbike front brake disc and caliper imagine how light and cool that would look?! I'm not sure yet, maybe one car type disc and caliper would give a more suitable rear brake force, but I've cut up the drum back plates now anyway so I'm committed to something along these lines, and it'll be interesting to see what works.
If you put the brake on the drive side of the diff, as it sounds like you're thinking, then the braking force will be applied to the wheels via the (presumably open) diff. So this means that if one wheel locks, the force on the other will be limited to that at the locked wheel. I'm not exactly sure what effect this would have on braking, but it would be somewhat different from a conventional setup where each wheel is braked separately.
samoht said:
If you put the brake on the drive side of the diff, as it sounds like you're thinking, then the braking force will be applied to the wheels via the (presumably open) diff. So this means that if one wheel locks, the force on the other will be limited to that at the locked wheel. I'm not exactly sure what effect this would have on braking, but it would be somewhat different from a conventional setup where each wheel is braked separately.
Thanks samoth, I am trying and failing miserably to wrap my head around this whole single disc set up! So yes it’d be one brake disc bolted to the casing of the open diff. Presuming I have a powerful enough disc and caliper to set my straight line brake bias correctly, then the issue is the balance through the open diff in cornering, as you say if one wheel locks or if I end up braking with one wheel in the air. Can’t figure out the consequences of that and if it’s in the “worth a shot” category or the “don’t be a smart arse, keep it simple and proven and just fit two discs you idiot” category. All thoughts and suggestions welcome…Did a load of work on an RCR years and years back great little car with the s
ttest gearbox in the world, utterly dreadful spoiled what was a fun and nimble car and turned it into a death trap, pulling out on a busy roundabout, going for second gear and then rolling for anywhere between 30 seconds and 5 years before second engages, I don't think I have ever come across a gearbox as bad as that ever, what the fk they were thinking I will never know.
Then my mate drove his nieces Fortwo, had to explain, it is a manual box of satan, drive it with an imaginary clutch pedal, go through the motion, let off throttle, pretend to push clutch in, then change gear, then clutch up before applying throttle.
Good luck, should be a cool little thing when it is done, especially since you have taken car of it's second biggest weakness, don't forget to silicone up the wiper linkage cover above the SAM unit.
ttest gearbox in the world, utterly dreadful spoiled what was a fun and nimble car and turned it into a death trap, pulling out on a busy roundabout, going for second gear and then rolling for anywhere between 30 seconds and 5 years before second engages, I don't think I have ever come across a gearbox as bad as that ever, what the fk they were thinking I will never know.Then my mate drove his nieces Fortwo, had to explain, it is a manual box of satan, drive it with an imaginary clutch pedal, go through the motion, let off throttle, pretend to push clutch in, then change gear, then clutch up before applying throttle.
Good luck, should be a cool little thing when it is done, especially since you have taken car of it's second biggest weakness, don't forget to silicone up the wiper linkage cover above the SAM unit.
Gassing Station | Readers' Cars | Top of Page | What's New | My Stuff