Longboard Wheel Braking System

So the lack of budget has made me choose longboard wheels for my first gravity racer build – the LGR-002. They are cheap, larger than skateboard wheels (so roll better, arguably, but at least offer more ground clearance) and have simple atatchment. Basically, the wheel holds the bearings, and then you just slot the whole lot onto an 8mm axle and tighten it up with a nut. Done. No hubs, no spokes, no rims. As i’ve seen with street luge, they are also capable of high speeds.

But there is the tricky subject of brakes, as I have mentioned in my previous blogs.

Well, I think I’ve come up with a design that is simple enough to work, and here it is.

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Essentially, each wheel will have a large washer screwed to the inside face to act as a braking surface. I have chosen Abec11 70’s Flashback wheels, as they have a flat inside face to allow this. The washer is 60mm in diameter (less than the 70mm of the wheel) 4mm thick, and with a 22mm hole in the centre which is exactly the same size as the bearing. I’ll mark out the washer for the fixing holes, drill them, and then use a small section of 22mm steel round bar to line it up on the face of the wheel. Then I’ll mark the holes through to the wheel, drill some small pilot holes and then screw the washer to the wheel. The screws will be countersunk to allow a smooth braking surface.

Then it’s a case of making up some pivoting brake arms with pads on the ends. They’ll have a return spring that pulls them against rubber stoppers, to keep the brakes off the wheels when no force is being applied. The tops of the brake arms will be linked together by a brake cable, much like in a bike brake. This cable will run into the cockpit of the car and be connected to a brake pedal.

I’ve not done the maths (primarily because I don’t know how) so I’m not sure how much braking force I can expect to see from this setup. I know that to increase leverage and braking force I’ll need to move the pivot point closer to the brake pad (or make the brake arms longer above the pivot) to give more pedal travel per mm of brake pad travel. ideally the brake pivots would have bearings etc, but I think a fat bolt with nylon washers and a bit of grease will have to do in the first instance. Nip things up nicely and then let the return spring take care of the rest.

Anyway, that’s the plan for now, so we’ll see how it goes.

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2 thoughts on “Longboard Wheel Braking System

  1. Like you, I am not a formula guy, I have to fly by seat of the pants or gut instinct. To me the beauty of gravity racing has always been that we are all pioneers to a certain extent. The only thing I would question about your idea would be if you can get enough force out of the small braking surfaces to slow a vehicle and driver ( I would have to guess no less than 250 lbs. total ) how much heat is that going to generate, how will it dissipate and will it get hot enough to melt the attachments to the composite wheels ? Brakes get smokin’ hot real quick. My memory blocks out the number of brake fails and near death experiences I’ve had trying to develop my own braking system and all the different designs I’ve tried. Keep at it and you’ll get there. Just be prepared for the majority of times that they aren’t going to work and have a survival plan in place.

    Liked by 1 person

  2. Cheers for the comment Donnie, always appreciated!

    Yes, I have wondered about braking force and heat myself. Of course, with enough leverage and pedal travel, force (in theory at least) shouldn’t be a problem. But as you say, that could generate a lot of heat.

    Assuming that my car is not a heavyweight though (i’m certainly not going to try to get up to 200kg as i would expect the bearings to overheat and puke the wheels) i’m wondering if the braking action will be on a par with bicycle rim brakes? They don’t get overly hot, although I am also aware that trying to brake a wheel near its centre is different to braking a wheel near its edge.

    Regardless, I figured I could mount the brake “discs” with nylon washers between the wheel and the disc to allow airflow on both sides of the disc for cooling, and to prevent heat-soak from the disc into the wheel as best I can. Maybe screw them on with nylon screws too (I dunno – something strong but with low heat conductivity?)

    I know air is pretty poor at cooling, but I figured some ram air style cooling vents wouldn’t hurt either, especially if the wheels end up being covered and out of the airflow.

    P.S. If you ever watch that F1 documentary I mentioned, let me know what you thought. The guy’s my hero! đŸ™‚

    Like

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