# Best Homemade Tools >  Shock dyno (or Shock absorber dynamometer)

## tonyfoale

A shock dyno is a measuring tool for analysing the dynamic characteristics of the the damper part of a vehicle shock absorber. Over the period of their existence there have been several basic types used. The main types in chronological order being;
1. Mechanical
2. Hydraulic
3. Electric

Hydraulic and electric are typically hi-tech and very expensive, controlled by computer they can driven to provide different wave shape displacements and can even be fed with real road data to simulate real life loading on the shock.

Mechanical versions are the traditional and most numerous. A crank mechanism is used to convert rotary motion from an electric motor to linear motion to drive the shock. Modern machines use a VFD (variable frequency drive) to alter stroke velocity, and the crank radius is usually adjustable (either in steps or continuously) to alter the maximum displacement.

My need is to develop rear shocks and front forks for classic racing motorcycles and my budget does not run to an hydraulic or electric device so I decided to build my own take on the mechanical type. The following shows the completed tool with an Ohlins shock mounted.

 Click thumbnails for full size.

Some machines use the crank to drive a Scotch Yoke to give sinusoidal stroke motion, others use a long conrod relative to stroke length to get a close approximation to a sinusoidal motion, the latter is the type that I decided to build because I see no special benefit in a true sinusoidal motion as long as the displacement is measured against time throughout the stroke. The other parameter that needs to be measured is the force exerted by the shock in response to the applied motion.

The following details the construction phase.

 
On the left is a 5 hp 3 ph motor which I kept from an old lathe which I had earmarked to power the machine. It was a flange mounting motor, I'd have preferred a base mounted type for ease of fitting. The start of the motor mounting is shown on the right being setup for making the holes for the mounting bosses.

 
Preparing holes for the mounting bosses and then machining the bosses level.

 
Attaching the motor mounting sub-frame to the base frame.

 
Here we have the motor mounting frame welded to the base, and also the mounting plate for a reduction gearbox.

 
Showing both motor and 25:1 reduction gearbox mounted to the part completed frame.

 
A couple of views showing the crank plate fitted to the gearbox output shaft. The tapped holes allow different maximum strokes of the shock.

 
On the left is the slider block and conrod. I had some 1" ID linear ball races so I got a length of 1" Thompson shaft and made an aluminium housings for the bearings. The shaft moves very smoothly with a high degree of rigidity. The yoke at the top is for mounting a shock or fork slider. The second photo shows a trial mockup of the assembly.

  
Making the top support bracket for the two uprights. Below are the two fixed lower mountings.

 
The sub assembly for mounting the bearing block and mountings for the uprights.

**** Photo limit reached. To be continued.

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DIYer (Jan 17, 2017),

Girrossco (Jan 19, 2017),

Schramm (Dec 17, 2017)

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## tonyfoale

****** Continued


Testing alignment prior to welding of sub-assembly.


Nearly finished, it just needs the load cell for measuring force, the string pot for measuring displacement and the top shock mounting yoke.

*Examples of shocks on test* 

 
On the left is an old Marzocchi fork for classic racing and on the right is a modern Ohlins race fork. Note the load cell and upper mounting yoke.

  
Upper mounting fixtures for front forks.

 
An Ohlins and a Sach rear shocks.

The input voltage and output signal of the load cell are connected to a dedicated instrument amplifier, which together with the displacement info. from the string pot is feed into a LabJack DAQ (Data Acquisition) system which then passes it on to a laptop for analysis and plotting in some software that I wrote for it. I have also potted some temperature sensors in small aluminium housings which I attach to the shock. Thus enabling temperature sensitivity to be measured.


Software opening screen.

 
The temperature sensors. Note the concave block to better fit the shock body. For those shocks with an external gas chamber there is a 2nd sensor for that.

* Examples of test results*


Older forks didn't always perform too well. Here are the diabolical characteristics of a standard fork. The problem was that the orifice for rebound oil was drilled such that it became blocked off way too early in the rebound stroke.

 
The much better characteristics of modern cartridge forks. On the left is the force/displacement curves with the force/velocity curves to the right. The 3 different sets are with the damping adjustments set to different values. These curves are several repeated runs superimposed.


An example of cavitation due to insufficient gas pressure in the shock.

One could write a book on shock dyno testing but the above is all that I have time for. Maybe it will wet a few appetites?

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freddo4 (Nov 5, 2021),

olderdan (Jan 13, 2017),

Paul Jones (Jan 18, 2017),

PJs (Jan 19, 2017)

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## tonyfoale

I forgot to add a link to a video of it in operation. Here it is;
https://dl.dropboxusercontent.com/u/...2/MVI_0106.MOV

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## DIYer

Thanks tonyfoale! We've added your Shock Absorber Dynamometer to our Motorcycle category,
as well as to your builder page: tonyfoale's Homemade Tools. Your receipt:















Shock Absorber Dynamometer
 by tonyfoale

tags:
suspension, measurement

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## DIYer

Thanks tonyfoale! We've added your Temperature Sensor to our Measuring and Marking category,
as well as to your builder page: tonyfoale's Homemade Tools. Your receipt:















Temperature Sensor
 by tonyfoale

tags:
suspension, measurement

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## penca

hello tony, beautiful and interesting dyno. did you made the load cell? riders being riders one would be better off connecting a shock dyno to a crystal ball then to the "subject" brain (or whatever we have for one - rider part talking hehe). thanks for sharing. any pics of pistons, valving stacks, chambers you want to share?  :Smile: 
pete

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## tonyfoale

> hello tony, beautiful and interesting dyno. did you made the load cell? riders being riders one would be better off connecting a shock dyno to a crystal ball then to the "subject" brain (or whatever we have for one - rider part talking hehe). thanks for sharing. any pics of pistons, valving stacks, chambers you want to share? 
> pete



Pete,

No I didn't make the load cell, that is an off the shelf item. The load cell itself is not overly expensive, but you need to have a decent instrument amp. as well. If I recall correctly the amp. was more expensive than one cell but I can use it for some other tasks which use other load cells. You can buy instrument amp. chips quite cheaply but you need filters etc. etc. I could have easily made an amp. but unless I got very lucky it would have required some development time which I would prefer to spend on developing the suspension.
I don't have many pix. of the valving of the stuff that I have been working on because it was always a work in progress. I'll see what I have though.

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## tonyfoale

> Thanks tonyfoale! We've added your Temperature Sensor to our Measuring and Marking category,
> as well as to your builder page: tonyfoale's Homemade Tools.



I have made a new post going into more detail about the temperature sensors.
http://www.homemadetools.net/forum/r...-sensors-56865
For anyone who wants to go deeper into the subject.

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## Jon

Congratulations tonyfoale - your Shock Dynamometer is the Homemade Tool of the Week!

We had an extraordinary week around here, guys. We broke our years-long record for the most pageviews on our forum, and we did it in style - with a huge list of great homemade tools, many of which could've won this award in another week.

I'm still processing all of the new members, and all of the new different forums linking to us - literally hundreds of different forums, representing every different DIY discipline under the net. The value of the high-end technical contributions that we're making to internet culture is unprecedented. That we're able to do this with such a high signal-to-noise ratio of technical content with virtually nonexistent drama, is a rarity among forums, and a testament to the quality of the contributors that post here.

A roundup of some of the nicest tools from this week: a Metal Bender by Vyacheslav.Nevolya, a Power Hacksaw by olderdan, a Lathe Belt Grinder by connan, Work Stops by mklotz, a Bridgeport Mill Upgrade by tonyfoale, a Magnetic Building Board by jjr2001, and a Countersink Gage by rgsparber. It was also a good week for homemade automotive tools, with: a Tire Spreader by dtech, an Engine Locating Jig by astroracer, a Front Shock Mockup Tool by astroracer, and two different carburetor work stands, including a Carburetor Work Stand by astroracer made from a carb spacer, and another Carburetor Work Stand by bobs409, made from old valves.

And yet another great milestone - this is tonyfoale's third Homemade Tool of the Week win, which means we have another 3-Time Tool of the Week Winner! You'll notice the 3-Time award trophy graphic in tonyfoale's postbit beneath his avatar.


 :Rocker:  :Clapping:  :Thumbs Up:  :Hat Tip:   :Hat Tip:  :Thumbs Up:  :Clapping:  :Rocker: 

Here are all of your winning tools:















Horizontal Milling Machine
 by tonyfoale

tags:
mill 















Drum Brake Grinder
 by tonyfoale

tags:
grinder, brake drums 















Shock Absorber Dynamometer
 by tonyfoale

tags:
suspension, measurement 






tonyfoale is in good company among this list of previous winners: rossbotics, mr95gst, Paul Jones, Christophe Mineau, immortalx, scorch, Brendon, Frank S, mklotz, Vyacheslav.Nevolya, jjr2001, and olderdan (all awards are viewable here).


tonyfoale - the cash prize is a $25 online gift card, in your choice of Amazon, PayPal, Giftrocket, or bitcoin. Please PM me your current email address and gift card choice and I'll get it sent over right away.


Congrats again and nice job!  :Thumbs Up:

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tonyfoale (Jan 20, 2017)

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## penca

thanks for the reply tony, yes the amp really is an issue with load cells, i tried to cheat with a very crude version and homemade strain gauge but had endless problems of delamination of the gauge, noise and general unreliability so i gave up. sadly here these instruments are prohibitive but then again one does with what one can have. edit: this was many many years ago when i was a young lad employed in a mx tuning shop. so that was memory served
hope you find some pics it`s always interesting to see what other tuners do to mod susp internals. 
a suspension dyno would be a dream too even if stuck to one or two tyre compounds
thanks again. pete

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## tonyfoale

> ...................... 
> a suspension dyno would be a dream too ..................
> thanks again. pete



Pete,
Now you are talking really serious money. As you said we make do with what we can, but good work can be achieved with thought in place of funds.
I have used my shock dyno for some top race teams because of its accuracy and because I have a lot of analysis features in my software that most commercial units don't have.

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## penca

hello tony i can`t imagine how much money  :Smile:  and not sure i want to know! for the graphs you produced i think your software must be capable of making a lot of work and save a ton of money testing. now with the lean angles track tyres are capable of i don`t think there is one successful racing team without a software like yours and dynos of all types. i always wonder how they factor chassis flex at +50º lean and how in that limit rider feel becomes an indispensable tool (or not). my experience communicating with riders has always been miserable to the point i had to go out but then i couldn`t do half so ... haha. i hope you come out with a helmet transducer mind reader some time soon  :Smile:

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## tonyfoale

> hello tony............... now with the lean angles track tyres are capable of i don`t think there is one successful racing team without a software like yours and dynos of all types.....



Pete,
In fact the race teams don't usually have shock dynos. That is left to the suspension companies who provide track support at races. So without the dynos the teams don't have or need the dyno software.
However, many top teams do use my software for suspension setup in general, rather than just specifically damper setup. I have sold a few thousand seats of my setup software to top race teams and most manufacturers down to the average enthusiast. See;
suskin_pages
I wrote the shock dyno software for my own dyno, although it could be applied to others.




> ..... i always wonder how they factor chassis flex at +50º lean and how in that limit rider feel becomes an indispensable tool (or not). ............



The high power available nowadays and the extreme lean angles possible have made chassis stiffness a very important variable in "on the limit" performance. Although companies like Honda and Yamaha have spent fortunes, trying to get a handle on this, it still comes down to testing on the track, trial and error in other words. Many teams have a choice of swingarms available for different tracks and conditions, all with different stiffness characteristics. Rider feel is very important and good riders can feel the difference between very small setup changes. Unless a rider feels happy with a bike he will not be fast.

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## penca

i agree on the "rider effect" not long ago i had a bit of an argument with a known journalist about that, he stood upon the idea that a rider must "adapt" and the "greatness" and all that...and me about the building a bike that makes the guy happy. i have not seen in all my years one rider unhappy with his bike getting the best of it or him for that matter. there were some talks about a torsion adjustable sort of chassis or chassis/swingarm but i can`t recall who was doing it (maybe you?)

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## Schramm

> ...
> Attachment 15977 Attachment 15978
> Showing both motor and 25:1 reduction gearbox mounted to the part completed frame.
> ...



Hi Tony, big fan of the book, very cool to see your build on a forum. Quick question: where did you source the gearbox for the 25:1 reduction of a 5hp motor? It looks neat and small, not like anything I've been finding on the used market.

I'm looking to build a dyno this winter, just need to source the more expensive bits before taking the plunge. I've toyed with the idea of a hydraulic setup as well, but finding a cheap linear proportioning valve hasn't been easy. I think it will come down to finding a good valve or reduction box that will determine the method.

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## tonyfoale

> Hi Tony, big fan of the book, very cool to see your build on a forum. Quick question: where did you source the gearbox for the 25:1 reduction of a 5hp motor? It looks neat and small, not like anything I've been finding on the used market.



It was a scrap one from a Segway, originally it was 25:1 but I wanted to test at higher velocities and was after something like 10:1. The Segway box was a double stage device but I modified it to single stage and now have around 5:1. I was a bit worried that the motor wouldn't handle that gearing but it works fine and I can get high velocities at short strokes as well as the longest.
If I was doing it again, knowing now that the motor can handle 5:1, I would do it with pulleys and a toothed belt.

 Click image for full size.

Here you can see a stock gearbox on the left and the modified one on the right. Note the different input shaft positions.

BTW. I have made several other posts on here about motorcycle related tools which might be of interest. Look here:
http://www.homemadetools.net/builder/tonyfoale

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