1948 Triumph Roadster Supercharged plus other stuff…

[gazzam]

I’ve had this car for 6 years and have only driven it a few times.

I probably shouldn’t have bought it but I was in a real gung ho phase at the time and absolutely had to have a car from the forties with suicide doors.

A Jag Mk IV was what I was really after but the only one for sale at the time was silly money and this looked interesting, if not (anywhere near) as pretty. It has a pair of tiny seats and a fold up windshield in the boot. With the bench seat this makes it a five seater!


I looked at it, but didn’t drive it. It started and had all the gears but I didn’t take it for a drive.
It wasn’t till after it was delivered ( it was 600km away ) and I registered it that I took it out on the road.

It runs well, but it’s just too slow. You spend more time looking in the rear view mirror checking how many cars you’re holding up, than enjoying the drive.

So I need to make it a bit better. Not a lot. Say up the cruising speed from 75 to 90 kmh.

I have a cunning plan for this, but before I try to make it faster I have to make it stop.

The brakes don’t work at all. The pedal has almost no resistance.
I put new wheel cylinder seals in when I got it, and that got the brakes working. But they’ve since failed.

After finding out what I could about the braking system in general and the master cylinder in particular, I removed the culprit.

It is strange. Its a displacement system rather than a piston with seals. The advantage, I think is that there is no linkage/lever. The brake pedal pushes a rod straight into a fluid chamber.
The disadvantage is that the displacement is so small, all the rest of the system has to be virtually perfect for it to work.
The system was “so successful that it was never used again” according to one article I found.
Most of the stuff I could find, and there’s not a lot, mentioned that the system is unreliable.

And there’s the rub. I prefer a reliable braking system. Particularly if I’m going to (attempt to) make it faster.

This is the master cylinder. The brake pedal attaches to the threaded end of the displacement rod on the right in this photo.










This is the business end of the displacement rod. That seal has seen better days.








So, rather than search for seals, I decided to put a more common master cylinder in it.
This is the one from a Mk VII Jag. Pulled apart and partly cleaned up. It’s identical to the one in the XK120.










And this is the brake lever.







It looks like it might be useable.

Thanks for looking. Advice very welcome.

[horrido]

Not often you hear "more common" and "Mk VII Jaguar parts" used in the same sentence. :-)

[akku]

Lovely cars. I have always had a curious yen for a Renown.

[gazzam]

After cleaning, the MK VII brake lever looked like it might work through this conveniently placed gap. Sort of the corner of the engine compartment.






The chassis is made of what looks to be about 3 1/2 inch od pipe. That’s it that the bolt is pointing at.


The original master cylinder goes through this mount that is bolted to the floorboard. It’s essentially the rear mount for the mc.










I turned up this bit of plastic to use as a plug in that mount.







That held the brake pedal arm centralish in the footboard hole. The vice grips stopped it from falling out.










Made a simple mount for the chassis side of the pivot.








And stuck a nut to the back of it.









Tacked to the chassis.









Found some spacers in the stash plus a piece of threaded rod to make a dummy piston to hold the mc in alignment.









Another simple bracket.









Tacked in place.










Trial fit (for the nth time)









More later.

Cheers.

[ovimor]

Any improvement... is an improvement!

"Life saving/confidence inspiring" re-engineering, like this >> truly worthwhile.

Just finish it 'soli..ii.ii..d', a crash stop is all aggro 😱

OVIMOR

[gazzam]

Brakes continued.
I needed to make a bracket to support the pivot - there was one on both the XK120 and the MK VII.
It’s really a cover plate that picks up the mc mount and ties it into the pivot. I made it out of three separate pieces of 3mm flat, shown here tacked up.







Welded the brackets to the chassis.









Then fitted the cover plate after it was fully welded and tidied up.













Also needed a fluid reservoir. The one from the MK VII had seen better days, but the top was useable. Bead blasted top shown here with the rusted out body.










Found a paint can that is the correct diameter and just soldered the old top straight on. I zinc plated the old top first so that the thread won’t rust. I’ll paint it with the cap screwed on, but not till after I know the brakes work. Same with the pedal assembly and mc body. Bad karma. Don’t want to risk doing all that extra if for some reason I can’t make it work.








Made up a bracket for the reservoir though, risky as that is…what with karma and all.










All piped up, ready to fill and attempt to bleed.







That’s tomorrow though.

Cheers.

[gazzam]

Okay, brakes are sorted. I think.
A fair amount of faffing around bleeding them.
I’d put a fitting into the front circuit (so I could use the original brake light switch ) that was actually a cross with one leg plugged.
After many unsuccessful attempts at bleeding this side of the system, I cut the plugged leg off and soldered up the hole, in order to lessen the volume of air in the fitting.
That did the trick and suddenly I had a nice firm pedal.
I’ve taken it for a couple of short drives and the brakes are getting better with each application.

So now I have brakes that offer a more than reasonable expectation of actually slowing the car.
This is a major advance. Time to move to the next stage in making this car a keeper.

I plan to add this:









For those not familiar, it’s an AMR500 supercharger.
Just to be clear, I’m not trying to get ultimate horsepower out of the engine, I just want it to have a bit more poke.

I’m very much out of my comfort zone with this, can use lots of advice..
Mounting it will hopefully not be ridiculously difficult.
I think it will fit in the front of the engine bay and be driven by a vee belt with a pulley piggybacked to the one on the front of the crank.

Getting it sorted, that could be another story.

Please feel free to offer any advice you can.

Thanks in anticipation.

[horrido]

There's a guy in Australia who makes supercharger kits for aircooled VWs using these little blowers. He might be able to advise.... joeblow.me/

[varelse]

Hehe. It's so tiny!
Was in for the ride before the supercharger came in to play, now there's no doubt about it!

What are you doing with all your extra shed space? Just pushing every thing out a metre so you have more room in the middle?

[kevins]

As far as fitting it goes, I would suggest the main considerations are.

Carb or injection

If carb suck or blow through

Wheather to include some form of intercooling.

Pulley ratios to determiine torque curve and prevent detonation.

Are ypu going to incorporate some sort of pressure relief for closed throttle.

[gazzam]

Thanks Horrido, I looked at his website, useful stuff there.
Spot on Varelse, the extra space is the best. No doubt it will fill up soon enough.
Cheers Kevin, plan is to suck through the original carb. Also no idea with pulley ratios. The unit has a 3” pulley on it and I thought I might stick a 4” on the car as a starting point. As I said I’m only going for minimal boost so no thought of an intercooler. I’m looking for advice on relief valves.
TBH I’ve not done much to the car. It’s coming up for registration so I thought I’d get it through that first. Not that it’s very rigorous for old cars, pretty much if it looks ok, nothing is falling off and the lights work, it’ll pass.
So I’ve done a few little tidying up tasks and that’s been it.

I’ve mostly been fiddling about with a Ducati 450 that I restored over 30 years ago. It hasn’t run for about 20 years so it’s a major recommissioning. I didn’t do plating in those days, so lots of rusty bits and pieces to make shiny. Hopefully I won’t have to get the spray gun out.

The Triumph didn’t seem to be of much interest, so I sort of lost interest in posting.

[jamesd1972]

Whoa - lots of interest here !
If you post it (Ducati sounds nice btw...) I'm reading it.
James

[logicaluk]

Not much interest.... I don't think so.
I'm definitely interested, so much so I looked in to the tiny supercharger, it looks like you will be right at the top end of the chargers useable capacity, and I would have thought it will be producing some pretty hot air.

Have you got the 1800 or 2000 engine?

More roadster pics please
Dan

[westbay]

Triumph Roadster, more! more! more!

[gazzam]

Thanks Dan, you’ve made me see something most people have probably known all along.
I thought if you wanted more power you just bunged on a supercharger. I missed the bit that size is important. (My wife was right all along)

I’ve only just realised that the s/charger passes ALL the air that the engine requires, not just boost on top of what the engine would normally use. (I did mention that I was out of my comfort zone with this)
This is painfully obvious now but it comes as a bit of a revelation.

Correct me if I’m wrong but I suppose the maths is this:
The engine is 1800cc so will need 900cc per revolution and the supercharger is 500cc per rev.
Therefore it needs to be driven at almost twice engine speed just to supply atmospheric pressure ie no boost.
So given that the s/c pulley is 3” maybe a 7” pulley on the crank would be a reasonable starting point?

Please feel free to point out any other basics of supercharging! Hopefully I will eventually get up to speed…

Gratuitous photo of 450, to make me feel better.

[Davey]

This is a great looking thing, watching with interest.

Love the brake saga and very intrigued with the supercharger outcome.

[horrido]

Bigger capacity blowers are common enough since Mercedes, MINI and others used them.

[logicaluk]

Aug 31, 2022 12:29:40 GMT gazzam said:

Thanks Dan, you’ve made me see something most people have probably known all along.
I thought if you wanted more power you just bunged on a supercharger. I missed the bit that size is important. (My wife was right all along)

I’ve only just realised that the s/charger passes ALL the air that the engine requires, not just boost on top of what the engine would normally use. (I did mention that I was out of my comfort zone with this)
This is painfully obvious now but it comes as a bit of a revelation.

Correct me if I’m wrong but I suppose the maths is this:
The engine is 1800cc so will need 900cc per revolution and the supercharger is 500cc per rev.
Therefore it needs to be driven at almost twice engine speed just to supply atmospheric pressure ie no boost.
So given that the s/c pulley is 3” maybe a 7” pulley on the crank would be a reasonable starting point?

Please feel free to point out any other basics of supercharging! Hopefully I will eventually get up to speed…

Gratuitous photo of 450, to make me feel better.

I believe the 1800 engine was used with a higher compression ratio in the early Jags maybe that could be away to pepit up or a smallish turbo to bring the boost in early.

[PhilA]

Not no interest, I simply missed this first time round.

Carry on please!

[kevins]

Given the car only makes around 65hp it must be flowing far less air than its theoretical displacement if you match the supercharger flow to the engine capacity you will get a significant performance increase They use the same supercharger on VW 1600 engines, there are even commercialy available kits, most of those seem to have what looks like around a 2:1 pulley ratio and claim around 7psi of boost.

In the ideal world you would measure the engine mass air flow, overlay this on the supercharger performance map and choose a pulley ratio, in your case I would build it with some way of measuring boost and intake temperature and just experiment with pulley sizes.