Clumber Rumble

[puffernutter]

All, I need some help from the collective!

I am running a Clumber Rumble at Clumberfest this year and my first attempt works, but not well enough!

So what is a "Clumber Rumble"; it is a variation of the hare at a greyhound track, only this is a rope (paracord in my case) running down a 7m wide track and we see how fast the Clumbers can go chasing it - fastest wins! To buy the equipment is expensive, so I have made my own, very simply a DC motor and speed control with a pulley (some Clumbers are faster than others!) and three unpowered pulleys. The paracord is 100m long so it is roughly a 40m long run with 5m across the top and bottom and 40m back (continuous cord).
My problem is two fold, my motor wasn't man enough (I think it was a car interior fan motor in a previous life, but on no-load it could do the 2500 revs, and the controller (Banggood special) couldn't handle the current and died! In my first trial we were only managing 4m/s and I need to get to 10 m/s That should be possible with a 5" diameter pulley and 2500 rpm. I would prefer a direct drive and any drive belt is another point of failure!

So, what I am looking for is a 12v DC motor that can run at 2500rpm on load and have a fair amount of torque. This is for 2 reasons, one that cord is dragging along the ground (so there is friction) and I also need an amount of tension so the motor will drive the cord with minimum slip. This is what sounded the death knell for the motor and controller I was using, when I increased tension to reduce slip, it upped the current and blew the drive!

So, any suggestions for a source of motor and DC controller

Cheers

Peter

 

[Barking Mat]

How long does it need to run for ?

A starter motor ? I.e. diesel / petrol engine type thing ?

Frequency controller for speed, with a flywheel ?

String round flywheel / drum type thing ?

 

[Johnnybravo]

Electric scooter or electric skateboard, but you are then into the realms of brushless motors and controllers, and most likely 24v minimum up to about 60v.
2500rpm with good torque off 12v is going to be a tough call I think.

 

[Agroshield]

Power = torque x rpm Power = volts x amps Torque = force x distance

Try to measure the force needed on the paracord. Tie a spring balance to it and run along pulling it, reading the force. Multiply that by the 2 1/2" radius of the pulley and the 2500 rpm speed to give a very rough power figure. That will tell you the current you need at the 12v supply voltage.

Be very conservative with your measurements. Make some wild guesses about how the force will vary with speed (you running against the 10m/s desired).

You do not say if there is any need for the string to accelerate from rest to that speed in any particular time. If your speed controller does not ramp up the speed, and you are trying to go from zero to 2500rpm in the blink of an eye, that might be what is killing the electronics. The slip you are experiencing is the controller's life-preservation strategy. When you have pulled the noose around its neck so tight that it cannot slip, it expires.

You could wrap the string round the pulley (capstan principle) to reduce the slip. The other option is to increase the arc of contact between string and pulley (look at a Subaru timing belt for inspiration).

 

[zzr1200]

Just a thought, what about separate large industrial wire feed unit off of a dead Mig, possibly 24v motor might have inbuilt speed control in the unit...... ,

 

[8ob]

Whats wrong with using a small petrol engine like a Loncin/Honda? That would run all day with no problems and give you control over speed etc without all the complications.

Bob

 

[Agroshield]

Just a thought, what about separate large industrial wire feed unit off of a dead Mig, possibly 24v motor might have inbuilt speed control......

What sort of speed do wire feeders work at? There is chart here: https://forum.weldingtipsandtricks.com/viewtopic.php?t=13566 and another brief one here: https://www.mig-welding.co.uk/forum/threads/voltage-setup-chart.33768/ (post #8) that seem to be saying below 10 metres per _minute_ He is looking for 10 metres per _second_ which is 60 times faster than those charts suggest (assuming they are correct).

 

[Anguz]

Whats your car? If not too expensive.. get a steel rim that fits.. jack the car up and use the rim as a drum
Sit in comfort while you drive it

 

[Morris]

Another vote for a n old steel rim. First saw this at an agricultural show in Yorkshire for terrier racing. Great fun if they caught the stuffed toy on the rope

 

[outofthefire]

I've seen modified push bikes used with lurcher setups, electric motor i'd look at treadmill or mobility scooter

 

[Hood]

Does it need to be 12v or can you use mains to power a small controller? I have a spindle motor from a small CNC lathe but think it is 180v DC for max speed. Not even sure what that is but I could look if you think it may be suitable.

 

[sako243]

Milwaukee brushless drill, just cable tie the trigger down

 

[eLuSiVeMiTe]

Milwaukee brushless drill, just cable tie the trigger down

Cordless power tool was going to be my suggestion.

 

[hotponyshoes]

I would think you would want a starter motor sized thing to get that sort of power.
A speed control for that is going to be expensive though so my suggestion would be a starter motor powered from a car battery and a correct sized wheel to get the speed you want.

The main problem will be motor cooling as starter motors don't always have fans but for 30 second blasts with rests inbetween it should be ok.

I would start by fixing a bit of plate onto the motor shaft somehow then experiment by tack welding tube onto that for your pully and winding the rope around a couple of times then once the correct speed is achieved wrap the tube in a bit of carpet or rubber to give the rope some grip.
You could make various size tubes that drop over each other or, depending on the size needed, make a rough shaft with a keyway and 3d print various size wheels that drop on as required.

You might want to go overboard with the motor power as the race conditions may not be the same as the test conditions.
Ie, even if you do the tests on the race track a bit of rain on the day might make the toy heavier etc..

 

[hotponyshoes]

Simplest way might be a radio controlled car with the toy mounted on top?

Although I think a plate of sausages might be the sort of bait required to get clumbers up to speed. . .

 

[brightspark]

the RACING whippet club near us use a 12 volt car starter took my working whippet one day and he did real well till he saw a rabbit near the woods and deviated and promptly did the business and brought it back he never won a prize but they were impressed

 

[hotponyshoes]

I have got a few 12v starter motors here if you want one, ranging from 1.1 to 4.9 engine sizes.
Also some 12v geared motors like you would use on a big hog roasting machine.

I have also got a variable power supply that might run them but it's a 2-man job to lift it. You are welcome to borrow that if you like although i think it pulls 20a or something flat out so you might need to borrow the generator on the day as well and you'll need a van for that!

Edit, there is also half of a mobility scooter in my projects pile. If I remember rightly the back axle/motor is there and the speed controller. You would have to figure out how it all works but potentially, the axle could be mounted off the ground somehow and if the tyres were ripped off the rims could be used to wrap the rope around. One rim could be built up with some old carpet or something to give a slightly higher top speed for the young dogs

 

[puffernutter]

All, thanks for the useful ideas. I want to use battery power as it needs to be portable. I also think an engine of any description (albeit a good solution) will just be too noisy. For clarification, the rope length is 100m around 3 idler pulleys and one driver pulley arranged in a thin rectangle. There is no animal as such being dragged, just some plastic bags to give the dog something to chase. I have some videos from the Rumble in the USA, if I can copy them - I'll post them for you to see. If I need to go to 24v, then I'll get a second battery! As I said I'd prefer to have a direct drive as it removes a single point of failure. I managed 4m/s, if I have a more powerful motor and less slip, then I should get it faster. It need to be variable as not all Clumbers run at the same speed!

 

[puffernutter]

@hotponyshoes, thanks for all those offers! If I can I'd like to keep it as simple as possible. The mobility scooter is a possible, I may have one lying around - see what I can find! If nothing, I'll come back to you.

Cheers

Peter

 

[puffernutter]

Just looking on eBay there is a seller with a 12v, 50A 4.500rpm no load "powertouch" motor - that if I remember correctly is for a caravan motor mover - I have one of those under the bench....!

More ideas to try!