Dynomometer low cost ?

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buzzkill

buzzkill

Mad?scientist
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SLO California
I was going over a Dynomometer in my head and looking at designs , I think I can put together a low cost fairly accurate one for maybe $200 or so ? . Make a disk brake type unit with a load cell and sparkplug wire RPM sensor this would measure either at the large spur gear ( motor power ) or the rear hub ( drive train power ).

parts 1. Carbon fiber disk brake setup https://www.kingmotorrc.com/product-km66002s 2. load cell 3, Arduino for measuring the load cell and rpm's 4. a axle that connects the Hum/Spur gear to the disk brakes 5. pillow bearings to run thru the axle 6, and arm the holds the calipers and has a 1ft extension ( =1 ft/pound of load on the load cell ) and a large plate to mount it all.
for the hub style you would strap down one wheel to stop it, for the spur type no need ,but you need to strap the car down also !

what do you think ? could be shippable to try it out also ( in USA)

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Seandonato73​

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You would still need to know barometric pressure, humidity, and a few other inputs for correction factors. But yeah for an extreme low budget build that sounds promising.

Losi DBXL G320
Many others....you know..
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Seandonato73 said:
You would still need to know barometric pressure, humidity, and a few other inputs for correction factors. But yeah for an extreme low budget build that sounds promising.
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you could manually account for that stuff , I mean if your at 10,000 ft don't dyno a motor LOL ! , I have a control/readout system already 95% built from my Composites press with a 7" touch screen I just need to change the Temp. input to a RPM input , it also has data logging built in also ! see www.masterpresses.com , that would be the interface and it could be programmable .
Seandonato73 said:
You would still need to know barometric pressure, humidity, and a few other inputs for correction factors. But yeah for an extreme low budget build that sounds promising.
Click to expand...
any idea what the differential gear ration is on most cars ? 1:1


Seandonato73​

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buzzkill said:
you could manually account for that stuff , I mean if your at 10,000 ft don't dyno a motor LOL ! , I have a control/readout system already 95% built from my Composites press with a 7" touch screen I just need to change the Temp. input to a RPM input , it also has data logging built in also ! see www.masterpresses.com , that would be the interface and it could be programmable .

any idea what the differential gear ration is on most cars ? 1:1
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No I unfortunately don't, I didnt run a wheel dyno, just an engine dyno. So the ratios wernt an issue. I know you pull in 4 the (direct gear) and then theres the rear end ratio and tire size that play a factor. But beyond that never messed with it much. I would think it would be a lot simpler when just using a fixed gear ratio to keep a pump within its rpm range.
Also the correction factor is so we all speak the same hp numbers no matter elevation, temp, humidity or what have you. So dyno at 10k ?

Losi DBXL G320
Many others....you know..
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buzzkill​

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Seandonato73 said:
No I unfortunately don't, I didnt run a wheel dyno, just an engine dyno. So the ratios wernt an issue. I know you pull in 4 the (direct gear) and then theres the rear end ratio and tire size that play a factor. But beyond that never messed with it much. I would think it would be a lot simpler when just using a fixed gear ratio to keep a pump within its rpm range.
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my plan was to attach a disk directly to the hub HEX ( if they are the same size ? ) but ya gear ration will effect rpm's , direct to the crank would be better , I need to look at that closer ( more cost IMO).
Actually you could adjust in math for the gear ration very easily when you download the data just add it to the equation.

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Direct drive with a love joy and keep the clutch set up, would make starting easy, amd have the ability to swap out to a different size clutch set up at will. And no gearing. I keep forgetting you said about a brake set up, I keep thinking about the hydraulic set up I have plans for.​

Yeah you could adjust, I'm sure theres a chart or something for the correction factor.​

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Losi DBXL G320​

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Seandonato73 said:
Direct drive with a love joy and keep the clutch set up, would make starting easy, amd have the ability to swap out to a different size clutch set up at will. And no gearing. I keep forgetting you said about a brake set up, I keep thinking about the hydraulic set up I have plans for.
Yeah you could adjust, I'm sure theres a chart or something for the correction factor.
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I can measure mine , just spin the large spur gear 1 turn and measure the turns on the HUB , WHAT is a LOVE JOY ?

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buzzkill said:
I can measure mine , just spin the large spur gear 1 turn and measure the turns on the HUB , WHAT is a LOVE JOY ?
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Ok the final drive on my ROvan 320 is 2.5:1 and I have a 16/58 gear set the gear set is 3.625 x 2.5 = 9.0625 final drive ratio so at 10,000 rpm the tires spin 1103 x's

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I copied this over from another thread , If the mods want to move it over thats fine , I just didnt want to over take the other thread
 

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Ok first your brake is way too small. Like woefully inadequate. But the design is good imo. You need more along the line of a 6 inch disk, and a brake set up off the rear of a 4 wheeler. That's should provide adequate braking force for the hp these engines should make. There was a guy on you tube, that made something similar for a 5hp Briggs engine. I'll see of I can find it.
 
Seandonato73 said:
Ok first your brake is way too small. Like woefully inadequate. But the design is good imo. You need more along the line of a 6 inch disk, and a brake set up off the rear of a 4 wheeler. That's should provide adequate braking force for the hp these engines should make. There was a guy on you tube, that made something similar for a 5hp Briggs engine. I'll see of I can find it.
Click to expand...
I based the disk on a carbon fiber dist from a 1/5 , I can double them also , I used it because it fits right over a HEX HUB but I think you are right ! , I;ll look at other stuff
 
Seandonato73 said:
Ok first your brake is way too small. Like woefully inadequate. But the design is good imo. You need more along the line of a 6 inch disk, and a brake set up off the rear of a 4 wheeler. That's should provide adequate braking force for the hp these engines should make. There was a guy on you tube, that made something similar for a 5hp Briggs engine. I'll see of I can find it.
Click to expand...
any suggestions ?? most all other disk require an expensive hub adapter to be made , the axle is 12mm Matches the crank , thats why I used the carbon fiber disk , bot finding much .
Seandonato73 said:
If it can accept the inputs I wouldnt see why not
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requires a $800 box for that ! the SW is free the box is $$$$
 
buzzkill said:
any suggestions ?? most all other disk require an expensive hub adapter to be made , the axle is 12mm Matches the crank , thats why I used the carbon fiber disk , bot finding much .

requires a $800 box for that ! the SW is free the box is $$$$
Click to expand...
Let me do a little digging and see what I can come up with cheap.
 
I just don't think those little discks are going to have the force to actually pull the engine down, if they do they wont last long. Like trying to stop a rig, with mini van brakes. Very different then stopping the vehicle when the engine is disengaged.
 
Depends also on how long and how many dyno pulls you will be doing against it? Think of a car coming down a long hill. You ride the brakes trying to maintain a speed. After awhile you get brake fad and no longer holds. Which now means your readings are off. The carbon fiber disks I do not think will work too well. Once you get them so hot the glue bonding them will probably start to de laminate. Best spot is direct to engine as you are showing. No influence on gearing to help or hurt the readings.
 
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