Hey guys,
I want to measure vertical loads on my car. It's a production car and does not have those convenient and accessible pushrods. How and where would you install strain gauges on suspension coilovers.
I think in case on my rear SLA I can redesign the coilover's bottom eye mount to have a uniform thinner section to glue strain gauges to, there is plenty of elbow room there.
But the front MacPherson is tricky. It is more tighly packaged and it has a bending moment. Is there a way to mount strain gauges on a MacPherson strut? Has anyone seen strain gauges on a MacPherson strut? Is it even technically possible?
Philip
Strain gauges on suspension coilovers
Started by
Supercar
, Sep 06 2005 04:26
4 replies to this topic
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#2
Greg Locock
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- 6,492 posts
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Posted 06 September 2005 - 05:27
No its completely impossible.
Mount 4 (at least) to the bottom of the tube just above the abutment to the hub. These can be connected so as to be insensitive to bending, and sensitive to axial forces in the shock.
However, you will observe that when the shock is moving in compression any axial force generated by the piston (ie the jounce valving) will not be seen by the strain gauges. So you'll need a pressure tapping as well.
You might have more luck replacing the top isolator with a load cell.
Mount 4 (at least) to the bottom of the tube just above the abutment to the hub. These can be connected so as to be insensitive to bending, and sensitive to axial forces in the shock.
However, you will observe that when the shock is moving in compression any axial force generated by the piston (ie the jounce valving) will not be seen by the strain gauges. So you'll need a pressure tapping as well.
You might have more luck replacing the top isolator with a load cell.
#3
Greg Locock
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- 6,492 posts
- Joined: March 03
Member
Posted 07 September 2005 - 10:00
I just thought of a possible way. Strain gauge the spring itself (in torsion) to give the spring load (or measure its extension), and then separately measure the tension in the shock rod.
#4
Supercar
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- 285 posts
- Joined: March 05
Member
Posted 07 September 2005 - 12:16
I think I understood why I couldn't measure any compression damping with strain gauges mounted on the strut body. The compression force is applied at the bottom of the strut, but the rebound is applied at the top. That's in case of a monotube "right-side-up" damper. Mine is a monototube upside-down, so I can't measure any damping forces with this method.
Installing strain gauges on the strut body is not possible in my case anyway. I have a threaded bottom spring perch very close to the knuckle tabs.
Strain gauging the spring will tell me the same information that I could get from a linear pot and a known spring rate, won't it?
I think the only accurate way would be to do something at the top of the strut. Maybe replace my camber plates with some fulcrum system and a load cell or a strain gauge installed on one end.
Philip
Installing strain gauges on the strut body is not possible in my case anyway. I have a threaded bottom spring perch very close to the knuckle tabs.
Strain gauging the spring will tell me the same information that I could get from a linear pot and a known spring rate, won't it?
I think the only accurate way would be to do something at the top of the strut. Maybe replace my camber plates with some fulcrum system and a load cell or a strain gauge installed on one end.
Philip
