DYNO eddy current brake. take 2!
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HeadSmess
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i dont forget about things and i dont give up... i simply stop and ruminate for a while. life keeps getting in the way 
found my lump of steel. just wanted to use it cus its nice and soft...magnetically and machining wise.
magnet disc...
fresh off the mill. obviously 24 neo magnets will sit in them there pockets. no need for glue. im never getting the one i stuck in so far back out!
ive decided the whole thing works better when the magnets are alternating in polarity. much better.
this just makes me realise how time can fly past...
tried writing a code so they would slowly spiral in rather than just be on the circumference, but other than rewrite a few thousand lines by hand, i had to put up with it. wont affect anything.
found my lump of steel. just wanted to use it cus its nice and soft...magnetically and machining wise.
magnet disc...
fresh off the mill. obviously 24 neo magnets will sit in them there pockets. no need for glue. im never getting the one i stuck in so far back out!
ive decided the whole thing works better when the magnets are alternating in polarity. much better.
this just makes me realise how time can fly past...
tried writing a code so they would slowly spiral in rather than just be on the circumference, but other than rewrite a few thousand lines by hand, i had to put up with it. wont affect anything.
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HeadSmess
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cheers. tis the machine, but i take credit for using it and it took me a while to set it up.
next mill/lathe i buy, im getting a surface plate and doing some scraping. makes the world of difference on cheap chinese muck
you got me in the mood to go take pics of what i just made...
back. phone camera sucks
just the hub. very small spigot to centralise on. what you cant see is its 50mm of 90mm round bar at the back...(life getting in the way...set of carbide tools i bought were 2mm too high, so i decided i would machine all 50 at once...now i got all these lathe tools i can use. but i had to do at least one for this job) now for some holes on a pcd, some countersunk screws, and all i need is the shaft and adjuster doodad. that gets things to the rotating/loading point...
then some v block type clamp to hold the shaft steady. scales... grrrr. scales.
brrr. getting cold. meh. go rug up and drill some holes
and it took me a while to set it up.next mill/lathe i buy, im getting a surface plate and doing some scraping. makes the world of difference on cheap chinese muck
you got me in the mood to go take pics of what i just made...
back. phone camera sucks
just the hub. very small spigot to centralise on. what you cant see is its 50mm of 90mm round bar at the back...(life getting in the way...set of carbide tools i bought were 2mm too high, so i decided i would machine all 50 at once...now i got all these lathe tools i can use
. but i had to do at least one for this job) now for some holes on a pcd, some countersunk screws, and all i need is the shaft and adjuster doodad. that gets things to the rotating/loading point...then some v block type clamp to hold the shaft steady. scales... grrrr. scales.
brrr. getting cold. meh. go rug up and drill some holes
just the hub. very small spigot to centralise on. what you cant see is its 50mm of 90mm round bar at the back...(life getting in the way...set of carbide tools i bought were 2mm too high, so i decided i would machine all 50 at once...now i got all these lathe tools i can use
then some v block type clamp to hold the shaft steady. scales... grrrr. scales.
Sounds like you have it all planned out. I humbly volunteer to risk my ride for the sake of testing her when its all together
I think Fabian is going to be pounding on your door to give this little beaut a go.
All joking aside I imagine it will be a very solid well built Dyno if your brake is anything to go by, Thank you for keeping us updated with all that sexy metal.
brrr. getting cold. meh. go rug up and drill some holes
I think I am going to have to drag the wood heater into the workshop myself in the next few days, not enough light or warmth to keep up with my desire to mess about in the workshop, Women don't understand our sacrifices.
HeadSmess
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boring....
as the title says, today was boring, literally.
the part ive been dreading...the part i knew would take all day...9am to...its 4pm ish now
the spindle.
how to bore a 25mm hole 150mm deep? my 22mm drill bit has only 120mm of flute to use!
once that was over, the rest was easy. just wasting time with a finishing tool, nice slow feed whilst turning slow with a funny tool...
rightio..
erm. boring the hole. custom boring bar using a lump of old HSS endmill as a cutter
then we started getting all the rust off the outside...note the mandrel in the chuck for concentricity
old lord poobah here decided he wanted a nice smooth finish so made a funky tool... well, taking 4mm off in one pass with HSS is always ugly
first finin pass.
there is no final pass!
but... there is a finished...semi finished product
so. a long brass plug goes down the hole. it has a hole bored through it, tapped to M14x1 (just cus i have that size handy, saves doing an internal thread) and another hole at right angles at the far end.
this spindle i made needs the small hole tapped, firstly, to retain the disc.
then its getting a slotted hole down near the end.
the hole in the brass plug should line up with this slot.
the previously posted magnet disc, will have a bolt through it, engaging with the brass plug.
then a lead screw is stuffed down the end of it, threading into the brass plug.
so when i turn the handle, the magnet disc assembly will move towards or away from the rotor.
a whole freakin day...im going out and getting something to eat...
as the title says, today was boring, literally.
the part ive been dreading...the part i knew would take all day...9am to...its 4pm ish now
the spindle.
how to bore a 25mm hole 150mm deep? my 22mm drill bit has only 120mm of flute to use!
once that was over, the rest was easy. just wasting time with a finishing tool, nice slow feed whilst turning slow with a funny tool...
rightio..
erm. boring the hole. custom boring bar using a lump of old HSS endmill as a cutter
then we started getting all the rust off the outside...note the mandrel in the chuck for concentricity
old lord poobah here decided he wanted a nice smooth finish so made a funky tool... well, taking 4mm off in one pass with HSS is always ugly
first finin pass.
there is no final pass!
but... there is a finished...semi finished product
so. a long brass plug goes down the hole. it has a hole bored through it, tapped to M14x1 (just cus i have that size handy, saves doing an internal thread) and another hole at right angles at the far end.
this spindle i made needs the small hole tapped, firstly, to retain the disc.
then its getting a slotted hole down near the end.
the hole in the brass plug should line up with this slot.
the previously posted magnet disc, will have a bolt through it, engaging with the brass plug.
then a lead screw is stuffed down the end of it, threading into the brass plug.
so when i turn the handle, the magnet disc assembly will move towards or away from the rotor.
a whole freakin day...im going out and getting something to eat...
HeadSmess
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some number crunching, showing how easy this is in theory...
If torque and angular speed are known, the power may be calculated. The relationship when using a coherent system of units (such as SI) is simply
P = \tau \omega
where P is power, \tau is torque, and \omega is angular speed. But when using other units or if the speed is in revolutions per unit time rather than radians, a conversion factor has to be included. When torque is in pound-foot units, rotational speed (f) is in rpm and power is required in horsepower:
P \text{(hp)} = {\tau \text{(ft} {\cdot} \text{lbf)} \times f \text{(rpm)} \over 5252}
The constant 5252 is the rounded value of (33,000 ft·lbf/min)/(2π rad/rev).
When torque is in inch pounds:
P \text{(hp)} = {\tau \text{(in} {\cdot} \text{lbf)} \times f \text{(rpm)} \over 63{,}025}
The constant 63,025 is the rounded value of (33,000 ft·lbf/min) × (12 in/ft)/(2π rad/rev).
seee if that posts properly, otherwise...
http://en.wikipedia.org/wiki/Horsepower
so.
lets say i have a foot long reaction arm. of course i will!
and my scales, in pounds, reads 10 when i load the thing down at 5000rpm....
so, take the equation...
10x5000/5252=
9.5hp.
rotational speed, measured torque...hp seasy
3.6 lb at 6500rpm? 4.45 hp...etc etc...
now, my only thinking bit at the moment is mounting this spindle...
so, i need the torque reaction from the magnet disc. i guess the easy way is to just make the slot slightly oversize and let the thing spin slightly on the shaft, is how ive been picturing it so far. other option is to mount the spindle itself on bearings, the slot is tight with minimal play, and the reaction arm is clamped to the spindle... lets me use plain old spring scales but i think a proper load cell is on the horizon...
If torque and angular speed are known, the power may be calculated. The relationship when using a coherent system of units (such as SI) is simply
P = \tau \omega
where P is power, \tau is torque, and \omega is angular speed. But when using other units or if the speed is in revolutions per unit time rather than radians, a conversion factor has to be included. When torque is in pound-foot units, rotational speed (f) is in rpm and power is required in horsepower:
P \text{(hp)} = {\tau \text{(ft} {\cdot} \text{lbf)} \times f \text{(rpm)} \over 5252}
The constant 5252 is the rounded value of (33,000 ft·lbf/min)/(2π rad/rev).
When torque is in inch pounds:
P \text{(hp)} = {\tau \text{(in} {\cdot} \text{lbf)} \times f \text{(rpm)} \over 63{,}025}
The constant 63,025 is the rounded value of (33,000 ft·lbf/min) × (12 in/ft)/(2π rad/rev).
seee if that posts properly, otherwise...
http://en.wikipedia.org/wiki/Horsepower
so.
lets say i have a foot long reaction arm. of course i will!
and my scales, in pounds, reads 10 when i load the thing down at 5000rpm....
so, take the equation...
10x5000/5252=
9.5hp.
rotational speed, measured torque...hp
seasy 3.6 lb at 6500rpm? 4.45 hp...etc etc...
now, my only thinking bit at the moment is mounting this spindle...
so, i need the torque reaction from the magnet disc. i guess the easy way is to just make the slot slightly oversize and let the thing spin slightly on the shaft, is how ive been picturing it so far. other option is to mount the spindle itself on bearings, the slot is tight with minimal play, and the reaction arm is clamped to the spindle... lets me use plain old spring scales but i think a proper load cell is on the horizon...
Fabian
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I like how you've sexed up your post with a bit of maths.
HeadSmess
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well, its there, it works. hmm. i gotta mount it on the lathe and take a video. anyways.
i was browsing just now and came across this...
http://atom007.heimat.eu/tmt/gsf_dyno.html
now, it might sound impossible, dyno an engine with just a microphone?
the explanation makes it clear. engine produces a given frequency at given rpm.
it takes so much power to accelerate a given weight to a given speed.
knowing the gear ratio and mass being moved, and the rpm, one can deduce the power required...
not catering in wind resistance which complicates the issue but hey...
stuck on a bench, testing the magnetos signal, rather than a mic...and just a heavy weight being accelerated, like an inertia dyno. one knows the mass, one knows the rpm, one knows the change in speed per second or acceleration...
so whyd i make this thing anyway? lol
i was browsing just now and came across this...
http://atom007.heimat.eu/tmt/gsf_dyno.html
now, it might sound impossible, dyno an engine with just a microphone?
the explanation makes it clear. engine produces a given frequency at given rpm.
it takes so much power to accelerate a given weight to a given speed.
knowing the gear ratio and mass being moved, and the rpm, one can deduce the power required...
not catering in wind resistance which complicates the issue but hey...
stuck on a bench, testing the magnetos signal, rather than a mic...and just a heavy weight being accelerated, like an inertia dyno. one knows the mass, one knows the rpm, one knows the change in speed per second or acceleration...
so whyd i make this thing anyway? lol
I like the look of that program, The wind resistance thing seems a bit of a pain.. Maybe just mount the rear wheel on some sort of freewheeling drum and strap the bike down with a load equal to riders weight and input 0 for the Cd value?
The rest of it seems fairly straight forward to produce, bit of veroboard, few components from Jaycar or the like, maybe a couple of spade terminals wired into the parallel with the CDI to allow quick and easy hookup if you felt like doing further dyno work.
Mount a Bicycle computer to the rear wheel, multiple magnets for more accurate reading as suggested..
May not be 100% accurate that way but should at least give enough information to determine if change X is "good" or "bad".
I dunno, I am just spitballing here.
All that being said I am still very keen to see how your project is panning out.16:
May have to stick the bike on the ferry and come give it a whirl :laugh2:
The rest of it seems fairly straight forward to produce, bit of veroboard, few components from Jaycar or the like, maybe a couple of spade terminals wired into the parallel with the CDI to allow quick and easy hookup if you felt like doing further dyno work.
Mount a Bicycle computer to the rear wheel, multiple magnets for more accurate reading as suggested..
May not be 100% accurate that way but should at least give enough information to determine if change X is "good" or "bad".
I dunno, I am just spitballing here.
All that being said I am still very keen to see how your project is panning out.
16:May have to stick the bike on the ferry and come give it a whirl :laugh2:
