Brakes! A more technical discussion

[Joe Kerman]

What kind of brakes did you use? How did you like them?  What did they cost? Were they worth it?

[Ray Scheufler]

Front calipers from a 4 wheeler. Left handed master from something. Sprocket as rotor.

They worked really well. Originally we had 2 masters but it was hard to brake in a straight line. We ruined the seals in mind master and went with a double banjo bolt to run both slaves off one master.

Price $300

Worth it? Probably. Our brakes were the only way we were competitive. We passed people by out accelerating and braking late.

We would like to find comparable brakes for much less if we were to build many more cars.

Ray Scheufler

On Oct 10, 2013 10:42 PM, "Joe Kerman" <jke...@gmail.com> wrote:

What kind of brakes did you use? How did you like them?  What did they cost? Were they worth it?

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[Jon Halverson]

Rear drum brakes. http://www.gokartgalaxy.com/4_5_drum_brakes_&_components.htm

They were barely passable.  Hard to get right and always had one side that wanted to rub.

~$100

not in hind site.  independent control was kinda cool for help in the corners.

Plan for the off season is to rebuild with front discs.  Just spend the money.  We now also have regen which is way more effective than the drums were.  We were able to break traction with the regen the other day... It might be set a little high.

Jon
Phantom Power Racing

[Tim S.]

Ray described Banshee's brakes well, but here's some more general information:

Brakes are always going to be most effective on the front due to weight transfer. Real cars usually have a built-in front brake bias of 75 - 80%, meaning the front brakes do 75-80% of the work and the rear only does 20 - 25%.

I saw concerns in the rules thread about brake fade -- being able to safely stop at the beginning of the race but not having brakes by the end. There are two causes for this: Heat and pad wear. Heat buildup causes rapid fading and is particularly bad in drum brakes, mostly because they are enclosed. There is no easy way to reduce fade when you are running drum brakes. Generally, drum brakes should not be used in a racing application. With disc brakes, a larger diameter rotor makes a huge difference in keeping things cool. I'd guess the sprockets we were using for rotors are about 8" in diameter. That was probably overkill. The other thing is to try to allow a little airflow around the rotors. They don't need to be fully exposed, you just don't want to completely encase them.

I know a lot of people run small disc brakes that look like they came from a mountain bike. These should be fine, but I'd recommend using the hardest pad material you can find. These brakes have small, thin rotors that are going to heat up quite a bit on the track. I don't think they get dangerously hot, but they certainly get hot enough to soften rubber pads. That's going to result in accelerated wear and may require you to readjust the brakes or maybe replace pads between races.

If anyone else decides to run hydraulic brakes, I found that running both calipers from a single master cylinder gave us much better modulation. Having a dedicated master for each slave cylinder gave us way too much braking power and made it far too easy to lock the front wheels.

Sorry for the wall of text. I care a lot more about the mechanical bits than I do about the rules :-)

[Tim S.]

Also, if I were to do it over again I'm confident I could have built Banshee's hydraulic brake system for less than $150. It's one of those things you do once, then slap yourself in the face and wonder why you paid so much. The most important thing if you do run hydraulics is to make sure your two slave cylinders are an exact match. A matching set of calipers from an ATV works great.

All the parts are on ebay if you know what to look for, and they're not that expensive. If anyone is looking to try this, feel free to message me on or off the boards, I'll be glad to help.

[Bill French]

I feel dumb for asking, but as I've been thinking about front disc brakes, how are you all attaching the discs to the harbor freight wheels?  Are you buying hubs from somewhere? (where?) Making them?  (how?)

I think i want to build a car with dual motors instead of a differential, so i assume i could use the same setup to attach sprockets.

[ransom1wi]

We put a plate on the harbor frieght wheels that they bolt to. We don't use them much because of the regen though.

Sent from my U.S. Cellular® Smartphone

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[Bill French]

What do you mean, "a plate"?  Below is a picture, did you all make the hub, or is that a piece you bought?  Is it just welded to the thin steel of the wheel?  Or is there something else going on there (inside the HF wheel)?  Is this the same setup used for the rear sprockets?

I'm 90% sure these are pretty basic fabrication questions ... but my skills are very rudimentary in this regard and i just don't know what I'm looking at.

[Alex McLees]

We welded a short section of steel tube to a round plate (maybe 1/4" thick). The inner diameter of the plate was large enough to fit the axle through, the outer diameter of the plate was large enough to let us drill and tap the brake disk bolt pattern into it. The disk brake is bolted to the plate, which is welded to the tube, which is welded to the HF wheel.

[Alex McLees]

We pretty much did the same thing for the rear wheels, except the bolt pattern was different for the sprockets.
Changing inner bearings was a complete PITA, I recommend leaving ample space (inner diameter of the plate) to remove them.
Also if you don't want tire changes to take 10+ minutes, weld up more than one set of wheels ahead of time.

[Tom Gralewicz]

Most brake rotors are cast so they don't weld very well (we managed to get one to hold on Red Lotus, but couldn't get the second side to stay on)

Red Lotus is a light car and uses mechanical disk brakes:

http://tncscooters.com/index.php?route=product/category&path=34_100

http://tncscooters.com/index.php?route=product/product&path=34_101&product_id=227

Mr. Fusion is heavier and used hydraulics

http://www.pocketbikeparts.com/Hydraulic_Brake_s/45.htm

Jake is a monster and we scrounged a foot operated go-kart hydraulic brake, similar to this:

http://www.pocketbikeparts.com/Disc_Brake_Rear_foot_23_inch_Brake_hose_p/atbr302781.htm

For next year we plan on making our own hubs to accommodate bolt on brake disks or sprockets.  The tricky part is fitting a small brake disk with a large bearing.

Tom Gralewicz

Chronic Maker

(414) 380-1716

milwaukeemakerspace.org

[Joe Kerman]

Here are some more detailed pictures of fauxrarri's brakes: http://imgur.com/a/IvTh7

The regen is so good from the dual motors and geardown, that the main method of slowing down is to let off the throttle. The hand brake lever is only used in case of emergency.  In a lot of cases the regen brakes are too strong, and you have to be careful how much you let off the throttle!

[Edward Cady]

Our car had.

1. One modified bicycle caliper with a piece of wood against the wheel.

2. It worked, but could cause excessive tire wear and steering problems if we could do high speeds.

3. They came off a bike the was donated.

4. Not in my opinion.  If our car could do higher speeds, one brake I believe would not be efficient enough.

I'm glad someone asked this.  We are looking into other safer brake designs for our next car that will be faster, much more faster.

Ed

[Jaimy Juliano]

Here is what I did for Cartastrophe. It's a heavy wall tube with a big washer welded on one side and 6mm coupler nuts to mount the disc on the other. I bored out the inside of the tube to make pockets for the bearings but you could just find tube that already has the right ID. We ripped the center hub out of the HF wheels (they tend to do that to themselves) and the bolted rims to this instead. You can also get hubless rims from Northern tool for like $9.

[Jeremy Bloyd-Peshkin]

Nicely done! That's excellent.

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Jeremy Bloyd-Peshkin

http://tinyworkshop.org

[Jaimy Juliano]

Thanks! Working on one for a drive sprocket right now :)

On Saturday, October 12, 2013 10:57:32 AM UTC-5, Jeremy Bloyd-Peshkin wrote:

Nicely done! That's excellent.

On Sat, Oct 12, 2013 at 11:56 AM, Jaimy Juliano <jjuli...@gmail.com> wrote:

Here is what I did for Cartastrophe. It's a heavy wall tube with a big washer welded on one side and 6mm coupler nuts to mount the disc on the other. I bored out the inside of the tube to make pockets for the bearings but you could just find tube that already has the right ID. We ripped the center hub out of the HF wheels (they tend to do that to themselves) and the bolted rims to this instead. You can also get hubless rims from Northern tool for like $9.

On Friday, October 11, 2013 6:58:49 AM UTC-5, Bill French wrote:

I feel dumb for asking, but as I've been thinking about front disc brakes, how are you all attaching the discs to the harbor freight wheels?  Are you buying hubs from somewhere? (where?) Making them?  (how?)

I think i want to build a car with dual motors instead of a differential, so i assume i could use the same setup to attach sprockets.

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[Edward Cady]

Nice! Very nice!

,Ed