Shock Dyno

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SR Racing
Posts: 1205
Joined: June 24th, 2006, 1:58 pm

Shock Dyno

Post by SR Racing »

Just gauging some interest. We have built a Shock Dyno prototype. It measures all the same things that any shock dyno does (only better <g>) And doesn't require 220V it uses low volume 100 PSI air. No, it is not like the ones sold on the internet with stop watches and manual keying into a spreadsheet. It has full automatic data aquisition and graphs, milspec'd sensors 20bit D/A, etc. Requires a standard laptop with USB port. Graphs can be displayed in multiple ways showing low speed/highspeed bump and rebound, linearity, etc. It looks like we can get them out of here for under $1800 which includes everything except the PC. We have demo'd the unit and looks like we have 2 sales now and we may do a round track show in January. We are using the prototype here and if we think we can move 20 or so, we will do a production run. Any interest here? (100% Warranty. If it doesn't do what you want, send it back and get a full refund.)
sabre1
Posts: 66
Joined: June 28th, 2006, 12:29 pm

Re: Shock Dyno

Post by sabre1 »

Jim,

Can you post some charts/graphs showing the results and maybe a pic or two of the unit itself? I have one of the units that uses a stopwatch and requires manual data entry into a spreadsheet; works OK but doesn't show what is happening at the nose of the shock curve.

-Jim
SR Racing
Posts: 1205
Joined: June 24th, 2006, 1:58 pm

Re: Shock Dyno

Post by SR Racing »

Jim,

Our unit is almost a clone of the frame that you have. However, instead it uses A milspec pressure transducer, a linear pot, data acqusition unit and power supply.
Currently we are feeding the data stream to a file on the PC and then it is converted to graphs with Excell, etc. We are writing our own graphing routines for actual use.
THe output graphs are the typical Force (Newtons or lbs) verses Inches per sec. We also have some linearity graphs. They are nice because they show the fulll stroke of the shock with a curve that makes readily apparent increasing or decreasing damping, defective spots, and hysteresis.

Your frame could be updated with the above components, saving you money.

The following are some pics. Sorry about quality. (Taken with the cell phone and no flash)
The digital intrument at the top is for testing only. This is the psi (or newtons) that will be displayed on the PC screen when doing tests.
Not shown are the standard Force versus IPS graphs that you have seen lots of.
This is simply the prototype and the actual unit will be much cleaner. (wires, etc)

[ external image ]
Prototype Assembly
[ external image ]
Linearity Graph of good shock
[ external image ]
Linerarity Graph of a defective shock example
sabre1
Posts: 66
Joined: June 28th, 2006, 12:29 pm

Re: Shock Dyno

Post by sabre1 »

Jim,

I apologize for taking this a bit off-track, but perhaps you can offer a bit of expertise regarding the shock test unit. While at the PRI show, I asked the folks that had one of these units on display about taking readings at 1 IPS or lower shock speeds. They told me that I needed to talk to their 'engineer' about it, but they did now offer a 2.5" diameter cylinder as an option to the 2" cylinder that has been sold for some time. Never found their 'engineer' and even after the show he never returned my phone call. So...., have you tried using a larger diameter cylinder to get some information about the nose of the shock curve? Thanks. And thank you also for all your help this past year.

Happy New Year!

-Jim
hardingfv32-1
Posts: 1014
Joined: December 1st, 2006, 8:01 pm

Re: Shock Dyno

Post by hardingfv32-1 »

Why are the piston type testers considered inferior in the 0-2 ips range when compared to the crank type units?

I seem to be getting good results down to the .30 ips range.

How could a larger cylinder help? The lowest pressure I use is 10 psi. with a 2'" piston. I would say that 5 psi would be possible if I had a gage with a 0-10 lb scale. This could get me into the .20 ips range.

Brian
sabre1
Posts: 66
Joined: June 28th, 2006, 12:29 pm

Re: Shock Dyno

Post by sabre1 »

Brian,

I don't think the larger piston would do much good for our needs - this is what the manufacturer offered when I inquired. I was just curious to see if they might have some improvements... The larger piston would provide more force for a given pressure and that might be useful for stiffer shocks at higher speeds.

Typically my lowest test pressures have been between 10 and 20 psi depending on the shock tested so I'm not getting much data under 1 IPS. Lower than that and the the shock won't move. I suspect that this is one of the areas where the crank type dynos are superior - the shock is constantly cycling so you can develop a graph that might be closer to reality than with the piston type. Another benefit is that the crank type will heat up the shock faster and reach an 'operating temp' that is probably more realistic than what the piston type can do.

BTW: I replaced my pressure gage with one that had a larger face and lower range than the one furnished by the manufacturer so I can more accurately test at the lower pressures needed to cycle our shocks.

-Jim
hardingfv32-1
Posts: 1014
Joined: December 1st, 2006, 8:01 pm

Re: Shock Dyno

Post by hardingfv32-1 »

I think the a smaller piston might be the answer for FV shocks. Our shocks never get that stiff to cause issues with high speed readings.

Brian
SR Racing
Posts: 1205
Joined: June 24th, 2006, 1:58 pm

Re: Shock Dyno

Post by SR Racing »

Jim,

Sorry about delay. I haven't been in here for the holidays. For the typical FV shocks, we found the piston being used works fine across all realistic ranges of IPS. (With 100+ PSI) For stock cars etc. shocks a 2" bore or 200 psi might be more in order. The only advantage I have been able to see in the motor driven units is the abilty to heat the shock. But a hair dryer works quite nicely. :lol:

A few years ago I spent a couple hours in the trailer with Joe Stimola while he showed me his shock dyno operation. That is my only experience with the motor driven units. Actually it seems (other than the temp thing) the air driven dyno does all the same stuff and you can drive the full length of the shock at a single IPS of your choice. While the motor ones may have more data output that I am not aware of, the linearity graphs (shown in this thread) seem very intuitive easy to read. Then of course you have the standard IPS/PSI graphs.

Jim
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