karl
Well-known member
I like it. Is ol smokey stockish? Would be cool to get a comparison between a stock motor and one with a cam, ect. Or see how much gain an air filter adapter ,ect gives.
I decided I wanted a dyno
- Thread starter Flyinhillbilly
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Kartorbust
Inmate #627
That's what the idea was behind this dyno build.
Flyinhillbilly
The great cornholio
It's a blueprinted AKRA bottom end with a real good 64cc (edit: it's a 14 cc head. I've been working on my hot rods again and got my numbers mixed up) big valve head on it. I made pulls with it until the header broke off and it was very repeatable. When the header fell off it lost about 3/4 ft/lb of torque.
Kartorbust
Inmate #627
I can't remember but was it an in/lb wrench or ft/lb? With the display showing triple digits my thought was either it's reading with a decimal on ft/lb or was all in in/lb.
Flyinhillbilly
The great cornholio
Ft/lb. it has a decimal. I could hold it steady at about 10.4 before the header fell off. I could close the valve fast and shock it higher because of the inertia, but I think 10.4 was my best steady number.
Kartorbust
Inmate #627
Can't wait to see more comparisons.
Flyinhillbilly
The great cornholio
My neighbor just built a zero deck predator with .0205 quench area with a rtc-8 head milled to 16cc, BSP-2 cam, arc +.020 rod, arc flywheel, and a home bored carb at 32 degrees of timing on 100 low lead. I'd sure be interested to see what it makes, but I don't know if he'd be willing to run it on there or not. I was making pulls with mine a couple of weeks ago and he said "well, that's about as hard as you can be on an engine" so I doubt he'll be on board.
I'll get the header situation worked out and do some tests with timing adjustments and then move on to nitro (percentage of course) vs methanol.
I'll get the header situation worked out and do some tests with timing adjustments and then move on to nitro (percentage of course) vs methanol.
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Whitetrashrocker
Inmate #952016
Tell your neighbor to Buck up. Lol.
Why wouldn't you need to know the length of the bar? A bar 4' long is going to read differently than a bar 1' long due to leverage. You can always say the load cell reads 20 lbs, but at an unknown length the reading is meaningless.
Flyinhillbilly
The great cornholio
Because there is no bar. That one measures the torque via twist and a load cell.
mckutzy
Well-known member
As I understand the bar need to be a certain length to determine the torque precisely.
An example..
An example..
anickode
Active member
You could, in theory, do this with no load cell at all. With the right transducers and algorithms, you could derive all your numbers from the flow and pressure being created by the pump, with the known constants of pump displacement and fluid viscosity.
in theory... yes.
it's far from practical though, just the changes in viscosity alone will ruin the measurement.
And the temperature of the fluid WILL change (thanks to the pressure)
Of course one could generate a lookup table with viscosity at temperature,
but even that has to be an interpolated value at some point which again will be inaccurate.
But then another inaccuracy kicks in (the pulsing behaviour of the pump)
IDK about the number of veins in FHB's pump but chances are the pulses are significant enough to be picked up during measurement.
And we're back to interpolation ...
giant flywheels are a pain to run (from a security standpoint) but in the end, due to the inertia they provide (evening out pulsing and other side effects)
and the more massive they are, the more you can ignore even their bearings and whatnot.
In the end you do not only end up with the much 'simpler' setup, you also have the easiest possible math to calculate the torque provided.
But truth is.. nobody want's to have a giant weight spinning in his workshop, for sure not at the rpms we talk about here...
if it catches on your clothes you'll break some of your bones, your skull even..
if it breaks free of it's fixture it'll create some serious mayhem (and again breaks bones if you get too close)
Sooo fluid pressure measurements is the way to go for DIY... IMHO...
and a load cell does make sense to cancel out most of that guessing and interpolation,
measuring "real" physical torque the old fashioned way (torque bar length and force applied)
'sid
it's far from practical though, just the changes in viscosity alone will ruin the measurement.
And the temperature of the fluid WILL change (thanks to the pressure)
Of course one could generate a lookup table with viscosity at temperature,
but even that has to be an interpolated value at some point which again will be inaccurate.
But then another inaccuracy kicks in (the pulsing behaviour of the pump)
IDK about the number of veins in FHB's pump but chances are the pulses are significant enough to be picked up during measurement.
And we're back to interpolation ...
giant flywheels are a pain to run (from a security standpoint) but in the end, due to the inertia they provide (evening out pulsing and other side effects)
and the more massive they are, the more you can ignore even their bearings and whatnot.
In the end you do not only end up with the much 'simpler' setup, you also have the easiest possible math to calculate the torque provided.
But truth is.. nobody want's to have a giant weight spinning in his workshop, for sure not at the rpms we talk about here...
if it catches on your clothes you'll break some of your bones, your skull even..
if it breaks free of it's fixture it'll create some serious mayhem (and again breaks bones if you get too close)
Sooo fluid pressure measurements is the way to go for DIY... IMHO...
and a load cell does make sense to cancel out most of that guessing and interpolation,
measuring "real" physical torque the old fashioned way (torque bar length and force applied)
'sid
anickode
Active member
I'm not arguing the fact that a load cell simplifies things drastically. Just saying it could be done.
You'd need transducers for pressure, flow, and fluid temperature at the orifice, then the viscosity temperature curves for the fluid, and engine RPM. And some pretty serious real-time calculation capability, which would pretty much mean making your own interface module and writing some rather extensive programming.
You'd need transducers for pressure, flow, and fluid temperature at the orifice, then the viscosity temperature curves for the fluid, and engine RPM. And some pretty serious real-time calculation capability, which would pretty much mean making your own interface module and writing some rather extensive programming.
As I understand the bar need to be a certain length to determine the torque precisely.
An example..
Well yes. 10 lbs of force applied at the end of a 12" bar would be 10 lb-ft, but 10 lbs of force applied at the end of a 24" bar would be 20 lb-ft. My point was just that if you don't know the length of the bar, then you can't calculate the torque. But with the gadget he's using, all of that is irrelevant.
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