Cable brake questions

[Master Hack]

The reason is not for strength. It's a replica of a 1932 Ford frame, which has a very specific appearance. In other words, it's built like that for looks.

That's cool and there have been other replicas here and all have been works of art. The point was the weight. No way a little mechanical brake is gunna be satisfactory. That 6" brake is for a sub 200# cart (SWAG). So I'm guessing you will be adding a body at some point? More weight...
Save yourself some grief and ditch the mechanical brakes for hydraulic. BTW a drum brake will probably be worse.
The above is just the opinion of a grumpy old man, there may or may not any basis in fact.

 

[Hellion]

That 6" brake is for a sub 200# cart

That's a good point and maybe two brakes would be better. I was reading past DIYGK posts on the topic; the mechanical disc brake seems to have major fans and major detractors. Lots of people use "locking up the axle" as the measure of effectiveness and some (most?) of the guys who said that were in the neighborhood of 150 lbs wet.

I have not thought about disc rotor size in conjunction with karts, probably because these you can't go too big before you're dragging it the disc on the ground. Also, some of these vendor supplied discs often look like they are galvanized or zinc plated (too slick) which does not bode well for effectiveness.

 

[Master Hack]

have not thought about disc rotor size in conjunction with karts, probably because these you can't go too big before you're dragging it on the ground

Size matters! The stuff i've salvaged off these crotch rockets are huge. Slightly differerent applicatioin, you say? Why yes it is. These 3 huge rotors by comparison are 12 inch.
(12 inch is a guestimate from another room.) thats for 500 lbs bike.
Weight is a big factor when compared to brake surface. There ya have the total of my "linear friction vehicle decellerator" engineering knowlegde.
just seems purdy basic to me.
if plan A fails, plan B needs to be bigger and or better.

 

[Jamie P]

I would love to go hydraulic. That was my first plan, but none of the kits I found had a long enough hose. Actually, that's not true. I bought a rear brake assembly for a Trailmaster minibike, which had plenty of length, but the way that caliper mounts with bolts behind the rotor, I simply couldn't make it work. I tried 20 different ways, and I couldn't make it work on a live axle. So, I went with the hand brake and cable, which was a flop. I should have known the cable would stretch, and the hand can't squeeze hard enough.

I know I could buy the parts to make a hydraulic setup, but I know nothing about getting a custom hose made and properly bleeding the setup. I may have to learn more about this if I want to make this contraption "safe".

And to answer Master Hack's question, yes this kart is heavy. It's compact, but with the cab, bed, oversized frame, etc. it's pretty hefty.

 

[Master Hack]

Yer making too much outta this. I’m in the process of doing the same kinda thing.
Get steel brake line, compression fittings, short hoses. Its not rocket surgery.
we’re here to help ya figger it out.

Edit: if you do not have rear suspension you don't need hoses at all.

 

[Master Hack]

Here is a hydraulic hand (cutting) brake. you can see a hydraulic master (crotch rocket) ,. It can just as esily be attached to a foot pedal. I think once I get the locations permanent I'll eliminate the hose and just use steel line.
It's easy to rethread the aluminum caliper for NPT threads. Forget the brake kits they are meant as a one size fits all.
Motorcycle salvage are a gold mine of suitable parts.
I'll leave ya alone , it's your choice now.

 

[Jamie P]

Here is a hydraulic hand (cutting) brake. you can see a hydraulic master (crotch rocket) ,. It can just as esily be attached to a foot pedal. I think once I get the locations permanent I'll eliminate the hose and just use steel line.
It's easy to rethread the aluminum caliper for NPT threads. Forget the brake kits they are meant as a one size fits all.
Motorcycle salvage are a gold mine of suitable parts.
I'll leave ya alone , it's your choice now.

View attachment 161134

This is helpful. I'm going to pull my dad in for help. He has access to a scrapyard where there is a constant inflow of motorcycles and stuff.

He also has experience with running automotive brake lines, and he has the flaring tools, etc. These conversations are helpful because my mind gets stuck in "This is a go kart. Look for go kart parts." Looking at other sources for parts makes a lot of sense.

 

[Whitetrashrocker]

I ran my hydrolic master behind the seat. The short braided line to the caliper.
I made a mousetrap lever system to connect to a solid rod up to the pedal.

 

[Denny]

I ran my hydrolic master behind the seat. The short braided line to the caliper.
I made a mousetrap lever system to connect to a solid rod up to the pedal.View attachment 161135

Hydraulic, hydraulic, hydraulic!!!!!
Now go and write it 200 times!

 

[Whitetrashrocker]

Spellcheck is drunk again.

 

[Master Hack]

conversations are helpful because my mind gets stuck in "This is a go kart. Look for go kart parts." Looking at other sources for parts makes a lot of sense.

I knew l could get ya to unnastan!
Congratulations, you are on the way to becoming a great junior hack! Your accomplishments will be admired by all!
Well, maybe not....
The biggest problem with motorcycle parts is the rotors. The hubs the rotor bolts are not compatable with kart axles. So eithe use different rotors or make hubs.
Chose wisely young grasshopper....

 

[Master Hack]

Thhose bigg werds are diffekult!
WTR has shown a nuther example of the hydrolok breaks!
Whats a spellceck anyway?

 

[Master Hack]

Have you seen the light?

 

[Jamie P]

So, I've seen the light, and I bought a hydraulic hand brake and caliper. It seemed like it was really going to work.

However, the banjo connection at the caliper was attached at the totally wrong angle, so I flipped it in order to direct it the right way. Then I lost all braking force, but there was a little pressure build up when I squeezed the handle.

I opened the reservoir to add a little fluid, and now I get zero pressure on the handle. It leads me to think there must be air in the system.

I've tried opening the bleeder and letting a drip out. Squeezing the handle forces it out faster. With the bleeder shut, if I squeeze the handle quickly a shot of fluid flies straight up out of the port nearest the bottom of the photo. I squeezed very slowly a few times, and a couple of the tiniest of microbubbles came out. I've pumped the handle 100+ times, and there is no change in pressure and no indication that any more bubbles want to come out. I've tapped the line up and down. The reservoir is at the highest point in the system, and the caliper at the lowest.

I even opened the bleeder and ran a bunch of fluid out while refilling at the reservoir, and nothing changed.

This was exactly my fear about a hydraulic system. I'm feeling very humbled by this basic system, and I'm completely frustrated. Does anyone have any troubleshooting suggestions or surefire ways to correct this issue?

 

[Whitetrashrocker]

Lets see how you mounted the caliper.
The bleed screw should be on the top of the caliper.
Getting the air out is a challenge.
Fill the reservoir and pump the master a few times to get some build up. Hold the pressure. Then Crack the bleed screw. A squirt of fluid and hopefully air will come out. Close the screw and re-pump the master. Repeat ad nauseum.
If theres a loop in the line, it can trap air in there and not move enough fluid to push the bubble down the line.
Light pulsing on the master as you were doing is good to get the air out of the master cylinder.

 

[Jamie P]

Lets see how you mounted the caliper.
The bleed screw should be on the top of the caliper.
Getting the air out is a challenge.
Fill the reservoir and pump the master a few times to get some build up. Hold the pressure. Then Crack the bleed screw. A squirt of fluid and hopefully air will come out. Close the screw and re-pump the master. Repeat ad nauseum.
If theres a loop in the line, it can trap air in there and not move enough fluid to push the bubble down the line.
Light pulsing on the master as you were doing is good to get the air out of the master cylinder.

Yes! You nailed it. I didn't pick up on that detail.

I took the caliper off, flipped it over and held it higher. Then I only had to do the pump, hold, release method about 5 times, and it tightened right up. That was terrific. I missed the fact that my bleeder was low, and that was the problem.

Thank you