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need brake for wheel - help?

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Groundhog

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#1
I've taken on a small job to make some kind of simple brake on each of 2 12" pneumatic tires. Just something to rub the tire. This is a concrete ornamental curb slip forming machine so I would like the threads to be enclosed. Not a lot of room - 6" to 10" would be ideal. The customer also wants some kind of lock or detent on the adjustment so that it doesn't change with vibration or whatever.
The problem is that when he is making a curb on a hill the machine wants to roll and not always in a straight line (or a curve if that is what he is building) so he needs to put some resistance one one tire or the other.
I could make something from scratch, but surely there has to be something already made available. I just can't think what it is. I've spent all day doing internet searches but it escapes me.
I'm thinking of something like this trailer jack only smaller:

camper jack.jpg

He's only left the machine with me for a few days, so I need to get going!

I'll post a picture of the machine here tomorrow.

Thanks again!
 

Dave Smith

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#2
do the wheels just ride on a straight axel that turns or is the axel fixed firm and the wheels have bearings in them---you will need to give us the width of the tires and if there is something on the side of machine to mount a brake mechanism---I'm thinking of a hinged board with a piece of tire rubber attached to have a spring and threaded adjuster rod to put pressure on tires---another idea is to have an adjustable clamp to squeeze on the sides of the tires like bicycle hand brakes---kind of like grabbing them with your hand--you will get many ideas when you get pictures of the machine---Dave
 

GoceKU

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#3
I've done something like this couple of years ago, and i used 12" scooter wheels with their disc brakes, simplest chinese one piston caliper and the brake levers from the same scooter, only thing i had to fabricate was mounts for the axle and welded couple of nuts to mount the calipers.
 

Groundhog

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#4
Pictures

sample.jpg This is what the machine does.

0720.jpg The machine with a new motor - I just made a new cover (starting caps were in the way of the old cover) but it is freshly painted and drying. Concrete goes in the hopper (via shovel) and is pushed to the right by a fist-like plunger at the bottom. The concrete is pushed through a form (not visible) then the texture is stamped or rolled into the curb by hand. Coloring is added as needed.

0712.jpg One of 2 tire/wheels that need a brake. The leg is a trailer jack so the machine can be leveled on the go.

0714.jpg From the front? back?

0715.jpg another side view.

0718.jpg showing the level adjusting crank. The big thumb screws are for more adjustments or removal of the leg for really tight places.

0719.jpg I forget what the hooks are for, but we can't use them for the brake.


Wheel/tire assembly: tire is about 12" tall and 2" wide at the tread. The wheel is about 3" wide and made of plastic or nylon.


Goals:
Simple.
Threads and moving parts covered to keep concrete out.
Narrow, cannot be wider than the tire.
Simple.
Not affected by vibration (adjuster arm that folds, a knob with a detent, has a thumbscrew or etc.)
Adjustable (not just on & off), able to "slow" rather than just hold in position.
Sturdy - it is a piece of construction equipment and is subject to abuse.
probably more requirements but it early in the morning.

Basic idea & what I will make if I don't find something better would be a threaded rod with a knob on the top and a smooth metal pad on the bottom to rub and apply pressure directly down on the tire. A "nut" would be attached to the lower part of the leg with the threaded rod moving up and down via turning the knob. I haven't worked out the thread covering (for protection from concrete) or the "lock" he wants on the adjustment.

I just think there really has to be something already made that can be readily adapted. I just can't think what that would be.

And I'm trying to do this in my unheated, poorly lit, ill-equipped garage because I have my motorcycle in the shop with the cams off. I'm waiting for valve shims for the valve adjustment. I don't want any grinding anywhere near the open bike top end!
 

RJSakowski

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#5
You could do something like the old time wagon brakes. Any old westernern with a runaway team will give you ample shots of the mechanism. Basically, a pivoting lever with a pad that rubbed on the tire of the wagon wheel. For the lock, something as simple as a bungee cord to hold the applied brake or a ratchet and pawl system could be used. That mechanism could be easily adapted from an automotive hand brake mechanism.

Google wagon brake and look at the images.

Since you have rubber tires, a steel pad would work. I would curve the pad to match the tire. For this mechanism, I would think that independent brakes would work but if you wished simultaneous application, it wouldn't be too difficult to design a linkage.
 

GoceKU

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#6
Disc brakes for this are overkill, the cart i modify weigh close to 400 kg, cam operated plunger from the front top corner operated by bicycle brake cables and levers is what i would do, just get the stainless steel cables because this machine is washed after every use and steel rusts no matter how much grease you put in.
 

Groundhog

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#7
Here is a crude drawing of what the owner & I have in mind;

brake 1 v1.png

I don't think it needs to be a full contoured pad, just a 3/4" round bar laid cross ways on the tire should work. The machine is light (about 125 lbs.?) and the tires are run at pretty low pressures so they are soft.
Anything with a fulcrum, lever, or pivot would be more complicated than need I think. Cables (bicycle type of action) would be too flimsy and apt to get destroyed in a construction environment..
 

Groundhog

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#8
Disk brakes are out because of the cost, but mostly because of the added width. He needs to get very close to stuff.
 

DHarris

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#9
I think I'd try a small flat plate instead of the round bar to rub on those knobby tires - a slip adjustment would tend to bite on the knobs and I doubt the tires are perfectly round anyway. a small flat plate (more like a ski idea) might allow better "slip" when wanted. ???
 

Dave Smith

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#10
are these steering wheels also---which wheels steer it? also is this unit hand pushed or which wheels drive it--- Dave
 

Groundhog

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#11
Dave, the 2 front wheels are moveable but do not steer. You need to loosen one of the big thumbscrews on each wheel and position the wheels for the radius you want to travel. I think that to make smaller turns and curves he just kind of kicks it to where it needs to be. The single back wheel is offcenter and is fixed. It travels just outside of the newly formed curb.
The wheels are not driven. The machine moves by pushing concrete out the back (the new curb). Like an octopus squirting a jet of water - only a lot slower! When he moves it from place to place he picks the front 2 wheels up and pushes it around like a wheelbarrow. It is very light.
 

Groundhog

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#12
To clarify, what I am calling the front is the end with 2 wheels and has the cranks and big thumbscrews, the electric motor end.
The back is the business end. The end where the concrete curb comes out. That is the hopper end.
Not evident in the picture is that the back end only has the single wheel on the one side. In operation the other side of the machine rides on the new concrete (or slip form).
 

Tozguy

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#13
What about using a length of channel that is mounted upside down on the horizontal part of the hook (frame) with a pivot pin out to the right (ref post 7).
The channel would rest on the center of the tire with some overhang. Run a length of all thread along the inside of the channel with a square nut that is captured between the channel and frame. The nut would act as a wedge pulling or pushing the channel away from the frame and exerting pressure on the tire. Without pressure the channel would only rub lightly on the tire but crank up the pressure and it should allow you to adjust the hold well.
Key issues are size of the channel and position of pivot point so the channel slopes away from the pivot point.
Sorry I'm not good at drawings.
 

Groundhog

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#14
Tozguy, If I understand you right what I plan (if I can't find anything else) is basically what you are proposing, only without the channel. I'll just use the all thread to push (more or less) directly in the tire.
McMaster has several types of all thread. I'm looking at some that is 1/2" x 10. That is 1/10 of an inch per turn.
 

Tozguy

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#15
My idea has the all thread running inside the channel, which would protect it. Both would be in a horizontal position running under the horizontal part of the hook. There would have to be enough room between tire and frame for a nut and the wall of the channel.

It is more complicated than your idea. If you add a shoe to do the rubbing on the tire with your plan it should work. Maybe install the all thread at an angle to the tire so you would get finer adjustment of the braking.
 

Groundhog

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#16
Tozguy, I think I understand your idea now and I like it. I've ordered some 1/2" -6 all thread, nuts, knobs, etc. I figured the coase threads would stay clean better and make for less cranking. Should be here tomorrow. Still not sure exactly what I'm going to do with it!
 

agfrvf

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#17
Here is a simple solution. Look at BMX brakes for Y unions. It stops a 200lb adult going downhill at 45mph. It should work for you. Three wheeled bikes have a locking brake lever.
 

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Groundhog

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#18
The BMX brakes could be made to work but would take some doing. First, I need individual braking at each wheel. I don't think the existing wheel/tire combo would adapt easily to BMX clamping type brakes. Adding discs would involve adapting the wheels and would have to be mounted onboard. Besides, there are no handles so no where to put the levers.
 

agfrvf

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#20
The BMX brakes could be made to work but would take some doing. First, I need individual braking at each wheel. I don't think the existing wheel/tire combo would adapt easily to BMX clamping type brakes. Adding discs would involve adapting the wheels and would have to be mounted onboard. Besides, there are no handles so no where to put the levers.
Groundhog look at the pic closer. This is a more of a drum than disk setup. There is not a typical C-clamp. Its a canterleaver type press. It is a mountain board so it uses a tether.
 

Bill W.

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#21
Have you thought about adapting a toggle clamp somehow?
They are those clamps that are used for holding a work piece to a jig.
Kind of a cam over clamp that has a rubber foot on one end and the handle on the other end.
They're adjustable (clamping pressure wise) and the rubber foot could be replaced with a small steel plate contoured to fit the tire...
 

Groundhog

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#22
BIll, a toggle clamp is a good idea and would be easily adaptable. I think I am committed to the coarse screw design if I can find a suitable foot or decide to make a formed plate. It's going to be play be ear when the materials get here. So anything still might happen!
 

Groundhog

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#23
Finished, installed and delivered. Finally!

0740.jpg (click to enlarge - sorry about the crummy picture)

Started with 4" of 1/2"-6 coil-thread rod and 1 coil-thread nut for each side. Big loose threads work for this application by being less likely to be affected by concrete/sand/dirt/etc., requiring fewer turns to adjust, and not needing lubrication. The top end was turned down to accept a wing nut which was welded to the coil-thread. The other end was turned and threaded 3/8"-16. I turned one end of a piece of 2 1/2" aluminum round stock to a semi half dome and bored and threaded a hole in the center of the flat side to screw on to the rod (with a lock nut).
One flat of the coil-thread nut was drilled and tapped #10-32. The opposite flat was welded at a 15° to short piece of 1/2" bar, which in turn was welded to the machine. I braised a wing nut to a #10-32 brass screw. The brass screw jams the coil-thread in the nut to lock it in place.
Pretty crude but works just like the guy was hoping. If he's happy I'm happy.
Now I can get back to my motorcycle!

We had a lot of good ideas here, and most any one would have worked. Thanks all.
 
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#24
I was just thinking of an angled piece welded to a flat and drilled thru the wheel mount a lever type to just kick down on the tire . Almost a wagon type but simpler . Swivel on n off.
 

Groundhog

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#25
The wagon type brake would work except that this needed to be able to put an adjustable amount of drag on the wheel (and maintain that amount of drag). So it was not just a brake, but also a speed governor for that wheel.
 
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