rusefi.com

Say we want to apply pulling and pushing forces to one side of the shock absorber and have an amazing Chinese YZC-526 https://www.ebay.com/itm/YZC-526-500kg-S-type-Column-Tension-Sensor-Weighing-Sensor-Load-Cell/153216109509 on the other side of it without any springs - would that make a stock dyno?

These sensors seem to have four wires but I am not totally sure what's going on with these wires.

3 or 5 horses he says


reciprocating motion


What are the keywords to get such amazing reciprocating motion from an electric motor?

SBR20

Electronic part of the inspiration https://honda-tech.com/forums/road-racing-autocross-time-attack-19/diy-shock-dyno-2325055/ - here the force is applied manually

One with a free falling weight? https://www.hotrod.com/articles/82884-buildling-shock-dyno/

https://www.eng-tips.com/viewthread.cfm?qid=357653 says "scotch-yoke drive"

Oh https://www.southbayriders.com/forums/threads/134217/ has exactly the pictures I need

https://www.southbayriders.com/forums/attachments/441907/

Hf. 3HP motor 220volt Only: $169.99 2.2kW VFD Inverter DELTA 3phase 220V Variable Frequency Driver VFD
lifting mechanism coming (crankshaft connecting rod) I have one cylinder engine for you

Remove piston and connect shock ... up down eccentric mechanism ...

What are the goals? I think you are looking to learn more about your shocks, such that you can tune shocks with unknown specifications, as well you could check if your shocks are wearing out.

I think a system design could be mechanically simplified by using a proportional hydraulic solenoid valve. A 3" piston at 100 PSI can exert 100PSI * pi * (3"/2)^2 = 706 lbs (3140N) of force.
https://www.agrisupply.com/grizzly-hydraulic-cylinder/p/87086/

This valve looks to be a ball valve with an electric DC motor. I'm sure a similar double acting valve can be found.
https://www.agrisupply.com/electric-boom-shutoff-valve/p/36896/

I think hydraulics and pneumatics do not give such accuracy like a rigid connection ...
Or if you have $$$

The goal is absolutely unrealistic - I would like to install some magnetic shocks on my miata so I would need a way to compare my current shocks to magnetic shocks with different amperage running through them.

I am thinking that manual design like https://honda-tech.com/forums/road-racing-autocross-time-attack-19/diy-shock-dyno-2325055/ is my most realistic first goal, which means that I am mostly concerned about figuring how to communicate with a Tension and Compression load cell. eBay says I need an HX711 mini board https://www.mouser.com/ds/2/813/hx711_english-1022875.pdf amplifier. I kind of assume there are four wires since two wires I use to feed voltage and two wires would produce very tiny response? How would tension be reported versus compression since these are forces in opposite direction? For sake of reasonable price I am thinking eBay s-beam load sensor. Kind of open question what is the load I need to go with - some videos of commercial units so up to 3000 lbs cells while it looks like they start at 1000lbs.

Keep in mind the load cells tendency to ring.
https://en.wikipedia.org/wiki/Load_cell#Ringing

This picture shows the ringing of one system happened to be at 83Hz and took about 900mS to settle down. However after what ever this system was, when it had the hydraulic fluid, it's frequency was 120Hz and settled in 40mS. Above picture from this app note http://www.thames-side.com/res/Application%20Note%20-%20Advantages%20of%20T16%20Fluid%20Damped%20Load%20Cell%20for%20Dynamic%20Weighing%20-%20February%202015.pdf

If you are looking for a fast dynamic response time, you will likely need to do some magic, or your data is likely to be flawed. The resonate frequency of your system will be largely be dependent the load cell. However what the load cell is connected to will also change the frequency, and such. In the above you may notice they emphasize without hydraulic fluid vs with hydraulic fluid. In your system if you use bushings, those will likely have some slop and will likely have small impact tendencies as the bushing will not be a perfect fit. Those small impacts when it changes direction will likely cause they load cell to ring. One way to deal with getting good data out of cell when it's ringing is to look for the min and max of the ring then average them together. If you cell happens to be resonate at 100Hz, then you look for a min and max over 10mS. The average between the two will be really close to the non-ringing reading.

There is also apn019 gleeble which includes some non-useful frequency equations. I'm not sure if that can be posted or if that violates some licencing or something like that. They seem to want you to provide information to get that paper. As well the equations aren't really so I'm just posting the app note name and company name.

Any how, beware the ringing tendencies. As well if you minimize the impact tendencies of the system, you'll minimize this ringing tendency, which minimizes the software magic.

Once upon a time, I was looking at the INA128. It seems to be a good load cell analog choice. I have not personally used it, but I understand it's a good choice for load cell designs.
https://octopart.com/search?q=INA128&start=0

There are several good app notes at TI's page for that chip.

Eval boards like this one in ebay can fast track the prototype.
https://www.ebay.com/itm/INA128-Low-power-precision-instrumentation-common-weak-signal-amplifier/172351798425?hash=item2820f7bc99:rk:25:pf:0

For a low cost linear measurement, you could try digital calipers. They typically have a serial port out the top side.
https://www.aliexpress.com/item/200mm-8-Inch-Digital-Caliper-Electronic-Carbon-Fiber-Vernier-Gauge-LCD-Screen-Micrometer-Measuring-Tools/32868362949.html?spm=2114.search0204.8.77.79e32c57dZqF8h

Brief overview of the serial interface found here. It notes the 1.5V signal levels, so with the STM32, I think we are OK with our 3.3V supply. No need for those external level shifting transistors. Just wires between this and the STM32.
http://nut-bolt.nl/2012/reading-digital-calipers-with-an-arduino/

The above article references this article, which gets into more detail. I recall there were 2X different protocols for these. This one is the most common, but beware there is another one that could be obtained. AKA get the plastic that looks like these, not those other ones with more fancy looking plastic.
http://robocombo.blogspot.com/2010/12/using-tis-launchpad-to-interface.html

This trick also tends to work with these DRO devices.
https://www.aliexpress.com/item/shahe-0-150-mm-linear-scale-dro-remote-digital-readout-linear-scale/32826807324.html?spm=2114.search0204.8.5.456612d3s2qULN

I made a DIY dyno based off the Honda forum post a while back. I used a 1,000kg load cell and linear potentiometer from injection molding machines.

It more or less worked, matches up with what I would expect a stock miata bilstein to look like. I never actually tried changing any valves, or rebuilding any shocks.

If I recall, the HX711 was way too slow. I bought some dev board for a fancy Analog devices ADC and got it up and running at very high speed instead. Ringing doesn't much seem to be an issue, but slop in joints on changes of direction are, so I filter those results out.

Noise on the potentiometer was always an issue, I looked into LDVTs and some other encoders and more or less left it there.



And some data, sorry for the lack of units and wacky scaling and no visibility. Pretty sure the last two are the software's fault and not my own.

https://imgur.com/a/bTfKXoD

deezums wrote: ↑

Tue Nov 03, 2020 1:06 am

I made a DIY dyno based off the Honda forum post a while back.

where are you located?!

Near the middle of Kansas, more or less.

deezums wrote: ↑

Tue Nov 03, 2020 1:43 am

Near the middle of Kansas, more or less.

Important thing we are in the same country Can I please borrow it from you in 2022?

Haha, not a problem! I probably won't build my own set of shocks before then anyway.

Just as a fair warning, it's a bit of a workout!