Vibration dampener-shock style
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Vibrations can be a tricky subject. To get the most benefit from a vibration damper like that, you need to have it tuned to work with the stiffness of your motor mounts.
The best way to tune them would be to have adjustable mounting brackets that you can move the damper up and down to give it more or less leverage.
Basically as your motor vibrates, it puts the most force on the mounts at the start and end of each vibration.
With a damper, the most force is in the middle of the vibration.
When you've got the mount and damper tuned well, the max force on the damper in the middle of the vibration is about the same as the max force on the mount at the start/end of the vibration
So yeah, tricky subject but some nice gains possible if you put the effort in.
The best way to tune them would be to have adjustable mounting brackets that you can move the damper up and down to give it more or less leverage.
Basically as your motor vibrates, it puts the most force on the mounts at the start and end of each vibration.
With a damper, the most force is in the middle of the vibration.
When you've got the mount and damper tuned well, the max force on the damper in the middle of the vibration is about the same as the max force on the mount at the start/end of the vibration
So yeah, tricky subject but some nice gains possible if you put the effort in.
Based on other posts it sounds like most of the vibration is at idle and can be greatly improved by increasing the idle speed slightly. My wife's old Honda Accord with a 4 banger has one of those dampeners running between the upper part of the engine and the firewall, the thing is still rough and when I have to drive it I keep my foot on the pedal to keep the r's up at a light.
My vibration problems definitely aren't restricted to idle! from 1,000 to 2,000 rpms I have very intense vibrations almost live a really bad driveline [but driveline isn't the problem]. As soon as I slip in the clutch at any speed it goes away instantly, so it's in the engine.
Good idea, Dougal, but there's another way that can work more easily: an adjustable turnbuckle in the linkage may be much quicker and easier to adjust. That methond is use on torque limiter to prevent engine twist under launch and works very well.
Good idea, Dougal, but there's another way that can work more easily: an adjustable turnbuckle in the linkage may be much quicker and easier to adjust. That methond is use on torque limiter to prevent engine twist under launch and works very well.
What type of engine mounts do you have?
Ah Jim ?
When you slip the clutch what are you doing exactly ? Is the trans engaged or disengaged when the engine vibrates the most .
The shock style dampener would do little to absorb the engines fibrations but alot to absorb any harmonics that would contribute to a vibration problem .
Low engine mounts seem to have more vibration than higher ones too.
Bruce
When you slip the clutch what are you doing exactly ? Is the trans engaged or disengaged when the engine vibrates the most .
The shock style dampener would do little to absorb the engines fibrations but alot to absorb any harmonics that would contribute to a vibration problem .
Low engine mounts seem to have more vibration than higher ones too.
Bruce
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That it goes away when you slip the clutch makes me wonder if it's not the clutch itself, or in that same general area. Things that pop to mind:
Warped / damaged / ill fitting clutch disc, pressure plate assy, or even flywheel.
Poor engine / trans alignment / fit
Also, I'm not sure it'd do this, but if the thrust bearing is sitting in the oil pan (like it is on many of these..), that vibration could be the crank walking back and forth, and when you bring in some clutch pedal it damps the motion.... Have someone cycle the clutch pedal while you watch the front pulley.
Does it do this w/ trans in neutral and just revving the engine, cycling the clutch pedal in / out?
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I'd always wondered about using air bags to support the engine and then shocks / other devices to limit torque movement. Would be complicated, expensive, and probably a pain to get it right.
Bad choice of words on my part again: I should have said 'let' in the clutch, not 'slip' in the clutch! Clutch is perfect and so's the whole driveline.
I have poor motor mounts. I fabbed up some boxes that fit inside the frame and on the lower piece I used Dodge 440 motor mounts, and old used ones at that. I need to upgrade my mounts and I have some different Lord Gel-rubber mounts to use. Waiting 'til I get my 220V wiring run so I can fire up the MIG again...
I have poor motor mounts. I fabbed up some boxes that fit inside the frame and on the lower piece I used Dodge 440 motor mounts, and old used ones at that. I need to upgrade my mounts and I have some different Lord Gel-rubber mounts to use. Waiting 'til I get my 220V wiring run so I can fire up the MIG again...
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Ahh... Can't remember if you've said this, but have you checked / adjusted the valves? I keep remembering something about some folks with bad vibration getting some relief by adjusting the valves. But I think it was for idle vibration issues.
Yeah.. Coming up with a "just in case" for that scenario might be real entertainment. Of course, there's a LOT of cars out there with no real "oopsie" provision built in, other than having two mounts that can counteract torque.
May be easier to go with the thought of hanging the engine in the bay with bungee cords. :rasta:
Bungees? Now I think you're on to something hah!
"Yeah.. Coming up with a "just in case" for that scenario might be real entertainment. Of course, there's a LOT of cars out there with no real "oopsie" provision built in, other than having two mounts that can counteract torque."
I just thought about that and envisioned a cantilever arrangement, somewhat like the vintage shocks. Like a guy has an arrangement with a lever and fulcrum, and the air bag mounted at 'lift' point to support engine, pivot point in center, and at the farthest other end a coil spring. Leave some slack on coil spring, and have a support plate under the air bags as per normal install. If air bag fails engine only drops a couple of inches until coil spring limits movement by stopping lever movement? Not nearly as complicated to build as it sounds. The MIG, where's my MIG?! But one point is that without some locator like this lever arrangement the air bags are very poor for lateral stability on the center axis top/bottom, that engine could move a lot sideways.
Yes, I adjusted valves and some small help but my problems may be in the small, hard motor mounts. Can't do much there until I get the wiring run for the MIG, then will do some all new motor mounts. I also wonder if it could be a faulty injector because I've heard that can do it too? I guess I should crack them one at a time and see if there's one that doesn't cause a miss!?
"Basically as your motor vibrates, it puts the most force on the mounts at the start and end of each vibration. With a damper, the most force is in the middle of the vibration.
When you've got the mount and damper tuned well, the max force on the damper in the middle of the vibration is about the same as the max force on the mount at the start/end of the vibration"
Interesting, I'm going to look further into this! I imagine that with some good motor mounts, one of these torque limiters and a harmonic damper one would have a pretty sweet setup.
"Yeah.. Coming up with a "just in case" for that scenario might be real entertainment. Of course, there's a LOT of cars out there with no real "oopsie" provision built in, other than having two mounts that can counteract torque."
I just thought about that and envisioned a cantilever arrangement, somewhat like the vintage shocks. Like a guy has an arrangement with a lever and fulcrum, and the air bag mounted at 'lift' point to support engine, pivot point in center, and at the farthest other end a coil spring. Leave some slack on coil spring, and have a support plate under the air bags as per normal install. If air bag fails engine only drops a couple of inches until coil spring limits movement by stopping lever movement? Not nearly as complicated to build as it sounds. The MIG, where's my MIG?! But one point is that without some locator like this lever arrangement the air bags are very poor for lateral stability on the center axis top/bottom, that engine could move a lot sideways.
Yes, I adjusted valves and some small help but my problems may be in the small, hard motor mounts. Can't do much there until I get the wiring run for the MIG, then will do some all new motor mounts. I also wonder if it could be a faulty injector because I've heard that can do it too? I guess I should crack them one at a time and see if there's one that doesn't cause a miss!?
"Basically as your motor vibrates, it puts the most force on the mounts at the start and end of each vibration. With a damper, the most force is in the middle of the vibration.
When you've got the mount and damper tuned well, the max force on the damper in the middle of the vibration is about the same as the max force on the mount at the start/end of the vibration"
Interesting, I'm going to look further into this! I imagine that with some good motor mounts, one of these torque limiters and a harmonic damper one would have a pretty sweet setup.
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The shock is a very interesting way to counter the side to side shake on shut down/startup. People have commented on the side to side shake of engines mounted on flat pads being worse than those wedged in a Vshaped cross member. A shock connected from something High on the motor to maybe a plate bolted on the firewall might cut down on the shutdown startup shake. Interesting Idea.
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Or..
Build your mounts such that you have a vertical "stack", with attachments at the top and bottom that goes to the vehicle, and in the middle you have connection to the engine. Air bag between top and middle, another between middle and bottom (and would be primary load carrier). Have coil springs parallel / coaxial with the air bags.. There's your "oopsie" override. In fact, I'd probably support the trans with the same setup, cross link the air bags on the bottom and cross link the ones on the top so that if you do have a deflation, ALL of them in a given position deflate. That way your driveline doesn't get into a real kink as it would otherwise.
Then you could use a shock "strut" to limit torque.. OR.. Put another airbag / coil spring sandwich in the horizontal plane at the top of the engine (or one air bag / coil spring assy on either side near the top) and you'd have a full air-isolated support system.
Complex as all get out, but tunable on the fly if you wanted. (Better go ahead and grab that engine-driven air compressor, yer gonna need it!) Maybe even have the air pressure in the torque-control bags controlled (or some way to modify valving on the shock strut) by boost?? More boost = more torque, so ramp up the pressure in the bags?
:grinpimp:
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Those are torque-control devices in most applications and don't bear the weight of the engine. If you used soft / hydraulic / pneumatic weight-bearing mounts in combination with a dog-bone / hydraulic shock / other device to control torque movement while maintaining a high degree of vibration isolation, yeah, it'd help..
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