I want to limit the maximum speed of a wheel automatically. This

how on earth is a gravity powered thing with little wheels going to be moving that fast

>>1188028
70mm diameter wheels at 1200RPM is only 15kmh (10mph)

I don't think that's an "only" amount of speed

>>1188032
https://www.youtube.com/watch?v=EahajVER2mo

It would be difficult to design. I'm sure there's programs out there that would help but getting exactly the right spring tension would be tricky. And I ran into the problem with the one on my home brew go-kart that they can kind of "chatter". If you're going at exactly the engagement speed (as you would if you were using it for a break) it will pick up a little until the engine (or thing rolling downhill) slows, then it drops out, freewheels, and picks up again in a jittery sort of fashion. It might have just been a problem with the clutch that i had sticking though.

Centrifugal clutches are not really designed to slip and cook quickly.

I assume you would have the clutch engage on a static drum as the brake? No problem for a few seconds or once in a while but if you are looking for longevity I would look into something else. A retarder of some sort.

>>1188034
>It would be difficult to design
Indeed it would. The axial doesn't spin, so I will probably have to design the clutch from scratch, rather than buy one

>getting exactly the right spring tension would be tricky
I'm planning on having the spring length be easily varied with the turn of a bolt, so I can quickly adjust it to a speed that I want
Although I don't know how viable this is within such a small space

Jittering is what I'm worried about.
How violent is this effect?

>>1188036
It will be engaged on a static drum for a maximum duration of 30 seconds, for a total of 15 minutes per week

I don't mind replacing the pads and drum every few months. How long would you expect something to last at 15 minutes per week, with long cooling down periods after use. I could make the drum several mm thick to help with high heat, if heat is the main problem. I could also make the drum out of aluminium for its higher specific heat capacity compared to steel

A retarder doesn't seem like a viable solution
I need the wheels to spin with absolute minimal resistance below the maximum speed

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>>1188044
sounds like a job for an eddy current brake

>>1188047
I've considered this, but magnets close to bearings slow them down considerably. I could always buy full ceramic bearings, but they are rather expensive

Also, I can't think of a set up that would allow for zero eddy currents generated below maximum velocity

>>1188044
I know this is /diy/, but check out towerhobbies or your local hobby shop; you're looking for a nitro RC clutch. They're a centrifugal clutch that goes into a metal bell housing that can be adjusted and tuned with different springs and material trimming to engage at different RPMs.

If you're using it for 15 minutes a week, but its likely to "stall" for 30 seconds straight, it might last a month. RC clutches are cheap, but the housing won't need replacement; only cleaning up of the melted clutch material.

Alternatively, you could use a centrifugal governor like the old steam powered engines used.

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The wireframe view of pic related is what physically exists right now

The wheel sits over the two bearings and spins freely on the axial

I plan on attaching the static drum to the 10mm wide, 8mm diameter steel rod between the two bearings

How should I do this? Ideally I'll not damage/weaken the 8mm rod.

The only thing I can think of would be a tight fitting ring with two grub screws that bite into the rod. However I would be surprised if the grub screws can grip tight enough and not just spin.

>>1188053
A nitro RC clutch inspired this idea, however I don't think a clutch design exists that can solve this problem. Generally the clutch is attached to an axial that spins. Whereas the axial I have is static, and the wheel spins upon bearings.

Get hybrid bearings bro.

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>>1188051
>It MUST be smooth. No abrupt stops, just a gentle sliding of the clutch to maintain a maximum speed
>zero eddy currents generated below maximum velocity

you don't even know what you want

>>1188047
This. Steel disk on the axle and a static electromagnet. Smooth as silk, low impedance that will gradually build as the speed increases. It would be easy to tweak because you just have to increase the current through your magnet until you get the right speed.

>>1188285
>you don't even know what you want
If I'm at 50% speed, I want to be able to get to 100% with no additional effort.

If I'm at 100% speed, I want to be able to maintain that speed whilst on a flat surface for as long as possible.
However if I go above 100%, I need the clutch to engage and gently apply friction to keep me at 100%

>>1188407
Electricity is not possible. I'd have to use neodymium magnets

>>1188269
I will look into this, ty

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>>1188285
>you don't even know what you want
see pic related

Below max velocity, there is no frictional/resistive force. Above max velocity there is a force that counteracts the acceleration of gravity

The clutch should never lock, just slide with varying levels of resistance

in europe we have a thing called sommerrodelbahn i dont know a proper translation basically a rollercoaster which goes downhill these things have centrifugal brakes to maintain a max. speed. Maybe you can look in such direction.

>>1188093
>Whereas the axial I have is static, and the wheel spins upon bearings.

You put the wheel on an axis and differentiate the clutch and wheel spatially with said axle.

>>1188532
>Electricity is not possible. I'd have to use neodymium magnets

it generates electricity you put into a load -> drag

>>1188027
I would go with some sort of regen controller and electric motor anon. Then u just twist a potentiameter or tiedown a trigger. Expensive but easy af. They sell kits.

>>1188027
How much weight is your vehicle? Basically, you are dissipating all that extra kinetic energy (1/2mv^2) in a centrifugal brake. How precisely does the speed need to be regulated?

If you have the space and the skills, I'd put a car alternator on the wheel and control the field to start generating power as it approaches max speed. Then dump the power somewhere (resistors o charge a battery). Similar to eddy current setup, but you can tweak the retarding characteristics in software.

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>>1188033
I love when the reply is just a youtube link. 80mph of a fucking skateboard.

Please no.

>be me
>watch street luge x games
>well, time to kill myself.
>nail a sheet of plywood to a 2x4.
>rip up skateboard and throw my roller blade tires on it
>rocket down hill about 5 times faster than anticipated
>lift leg at all for stop and death wobble ensues
>guessiwilldie.jpg
>jump state highway through traffic witout getting ran over
>only 2 feet high but flying
>old lady mowing her yard
>i crash into push mower.
>1 time use street luge explodes
>i totaled a push mower on a fucking skateboard and had to buy a new one.
>almost gave an old lady a heart attack
>the cops showed up and didnt believe me
>start picking splinters out while old lady makes us all tea
>tell the cops again what happened as my buddy brings the camera.
>the cops want a copy.
>mfw

>>1188027
How about a computer controlled setup? 2 rotors, one with metered markings on it that a raspberry pi can read and deduce current speed from (like a photo tachometer) and the other with a brake that is actuated by the raspberry pi above a specified speed.

>>1188658
Can you give me a few more details or a diagram of what you're proposing?

>>1188673
Between 75kg and 100kg
It doesn't need to be very accurate, but it needs to be easily variable via a twist of a bolt or something similar

>>1188653
>>1188671
>>1188699
The problem with this is that everything has to be contained within the 70mm wheel. I could buy and use 80mm diameter wheels, but it all has to be within a very small space.
I probably should have mentioned this earlier, sorry

>>1188676
I'm dying...