Ben Nelson's Electro-Metro Build thread

[MazdaMatt]

I saw in your vid that you didn't plan on keeping the coffee can. Wise choice

power vs manual:

A MC and booster don't "work together". They are independant parts of a system. The booster exists ONLY to convert pedal travel into a pushing force gainst the MC. In older systems there was no booster, your pedal moved the MC directly.

The difference between a boosted and non-boosted MC is the size of the piston - the action ratio, i suppose. A MC designed to have a booster needs to be pushed harder than one that does not. If you simply take a MC from a scrap yard that was designed for a non-power brake car, then mount it where your pedal's pin pushes the booster, you'll get braking force. You would need an adapter plate made because that MC will not have the same holes as your where your booster mounts on the firewall.

[MazdaMatt]

john beat me to it.

I don't think, however, that you'd need to spend the money on racing supplies for this car. Unless they are reasonably priced in your opinion. Junk yard would work just fine.

edit: oh, it was only 50 bucks. Can you do cheaper than that with a sketchy pump? You can't do safer.

[Tango Charlie]

You guys are way to safe to have any fun.
I agree, however, that manual brakes would be much more reliable (SAFE, OK?) than rigging up a power assist system. Probably just as much work, too. But don't stop thinkin' and tinkerin', Ben.
I thought I read somewhere that somebody drilled holes in the back of the booster to relieve it to atmospheric for easier pedal force. Was that the Mullet? Or did Darin do that in the Forkenswift?

[johnmyster]

Originally Posted by MazdaMatt

john beat me to it.

I don't think, however, that you'd need to spend the money on racing supplies for this car. Unless they are reasonably priced in your opinion. Junk yard would work just fine.

I just can't think of any cars that didn't come with assisted brakes in our lifetime. I mean really. That's using the WAYBACK machine.

Perhaps an old VW? Maybe? Maybe? I have no idea.

[MazdaMatt]

Check this out, ben:

7/15/04
Another junkyard trip and I have more parts. I found a Metro LSi gauge cluster with a tachometer. And some Toyota brake line plumbing parts so I can use a Honda brake master cylinder on my Suzuki/Geo. This way I can have manual brakes without drilling new mounting holes. Yes, the Honda master cylinder bolts up to the Suzuki firewall, but the Suzuki master cylinder doesn't. Here's a picture of the test fitting. The brake line part I got was a three-way line splitter. This is necessary since the Honda master cylinder only has two outputs, I need three to use a Suzuki proportioning valve.

LINK

The picture in the link is dead, but this guy is saying that a honda MC has the same bolt pattern as the swift (metro?) brake booster. That means you could unbolt your booster/MC and bolt on a honda MC, straight up. I would recommed taking off your booster and making a paper template of the mounting holes and pin hole and see if this guy is right. This could be a DEAD SIMPLE swap.

[MazdaMatt]

Yes, some rabbits came with manual brakes. But as I said before, the cylinder is just a cylinder, it is sized according to its purpose. So maybe a MC from a boosted pickup would work fine unboosted in a metro. but check out the above idea first... sounds great.

[johnmyster]

Originally Posted by MazdaMatt

Yes, some rabbits came with manual brakes. But as I said before, the cylinder is just a cylinder, it is sized according to its purpose. So maybe a MC from a boosted pickup would work fine unboosted in a metro. but check out the above idea first... sounds great.

See, I was thinking that too. But then, my dad's GM fullsize gets more braking action NOT because it has a smaller master cylinder, but because it has BIGGER wheel cylinders and pistons in the calipers.

Looks like the honda solution may have trumped all Rube-Goldberg ambitions.

[MazdaMatt]

THIS THREAD

...explains how to use your (caliper) piston size and your pedal ratio to determine a suitable piston. I think that what I gathered is that smaller will give you a softer pedal and more travel and larger will give you a harder pedal with less travel. So you can likely combine this advice and the previous and find a "relatively small" honda MC (13/16ths?) and bolt it right on there.

[bennelson]

Thanks for all the brake info guys.


I had a chance to play around tonight working on a throttle for the car.

I had the control stick off the forklift I took apart in my driveway in January.

The control stick is attached to a big aluminum box and has a button on the side (horn?) and a toggle switch on top, which I think was for extending the forks.

Opening the box, I could see there was a double-cam on the stick, 4 micro-switches, and a potentiometer.

Setting my Ohm meter on the wires from the potentiometer, it pretty much read all or nothing. When I turned up the setting on the meter, I could see it was actually a 1 mega-ohm potentiometer, I just couldn't see it on the setting I was using.

The whole assembly is designed so that when you turn the stick, the first micro-switch turns on, then the potentiometer starts reading, going up to maximum, then the second microswitch activates.

The other thing that is kinda neat is that the potentiometer turns the same way whether you push or pull the stick - it goes both directions.

I was able to pull out a TEENY TINY set screw and slide the potentiometer out. I then replaced it with a 0-10k ohm potentiometer from Radio Shack

I screwed down the entire pot box assembly to a piece of wood where I also attached the cable end of the throttle cable. I put two screws into the plastic handle of the forklift stick control so that pressing on the gas pedal pulls the stick. I also added an additional spring to help with the additional weight of the stick.

I connected my ohm meter to see that I would normally have 0 ohms, and should have up to 5K ohms when the pedal is pushed.

Sure enough, it measured up on my meter.

Did a test run. The "go pedal" is a little stiff to push. Also, it's a bit touchy, sort of hard to do a real smooth acceleration. The actual mechanical connections will need to be improved for the final version.

Again, I am simply experimenting, using what I have to figure out how all this works, without spending a fortune.

This all makes a lot more sense with some photos. I will take some tomorrow for ya.

-Ben

[celblazer]

Originally Posted by johnmyster

I just can't think of any cars that didn't come with assisted brakes in our lifetime. I mean really. That's using the WAYBACK machine.

Perhaps an old VW? Maybe? Maybe? I have no idea.

I resemble that remark. My 65 Mustang is manual 4 wheel drum brakes and heavy as hell. Power and disc were options. It's even a single master cylinder. Can we say instant death if any wheel cylinder leaks?