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  1. PTwizz

    I need an estimate for the polar moment of inertia

    The corner weights and track wheelbase are not enough to determine pitch moment. E.g. a mid engined car might have a far lower pitch moment for the same corner weights than a front or rear engined car. Pete.
  2. PTwizz

    Trailing arm roll center

    My understanding was that IC would be at an infinite distance to the side, on the basis that the vertical motion represents an infinitely large radius. What this probably shows is that the conventional means of establishing RC height does not hold true when values are very large (or small). I...
  3. PTwizz

    Trailing arm roll center

    My logic runs thus: Using the conventional means to determine roll centre height, the projected instantaneous centre of motion of each wheel is an infinite distance away to the side. A line connecting that centre to the contact patch will therefore be at ground level (because it connects to the...
  4. PTwizz

    Trailing arm roll center

    Another way to visualise the problem: If you apply a lateral force to the body at roll centre height, no roll will occur. Apply the force above roll centre height and the body will roll away from the force, apply force below roll centre height and the body will roll towards the force. Your...
  5. PTwizz

    4-post test rig for damper setup

    I suspect 'grip disturbance' is probably the same as, or a direct function of, contact patch load variation. I assume the force/time curve is force measured at the contact patch. The object would be to keep this curve smooth, with rates of force change kept to a minimum. This approach will lead...
  6. PTwizz

    4-post test rig for damper setup

    There is a great deal to be gained from 4 post testing without any body actuation. Inputs would usually cover heave, pitch and warp modes, each using a sweep of frequencies from 0.5Hz to 30Hz. This can also be done with some simulated downforce (using air actuators with minimal damping and...
  7. PTwizz

    Damper Gas Pressure

    When comparing theoretical forces to track experience (Krazan) it is easy to underestimate the effects of gas compression (causing rising rate) and temperature (causing increases in rate and preload). If the gas reservoir volume is (typically) 3 times the volume displaced by the shaft, then the...
  8. PTwizz

    Energy cost of manufacturing small car

    DRWEBB - You are, of course, absolutely right in that there are far more emissions involved than just CO2. I suspect that this is also true of the manufacture and subsequent recycling of much of the material used in modern vehicles. If it comes down to a balance between short term local...
  9. PTwizz

    High Speed Rebound, needless?

    Bildon, 'Excessive' hub velocity is that which, combined with the unsprung mass, tyre stifness and tyre damping, causes 'unacceptable' acceleration and resultant contact pacth load variation. In simple terms, the harder you throw the wheel at the ground, the harder it hits and tries to bounce...
  10. PTwizz

    High Speed Rebound, needless?

    There is no hard and fast line between 'low speed' and 'high speed' damping. From a damper engineers point of view, that line is where high speed adjustment (shims, valve etc.) becomes dominant over low speed (bleed) adjustment. High speed rebound will, as suggested above, control wheel descent...
  11. PTwizz

    Frequency Selective Damping

    Following McLaren Racings announcement that they are using Koni FSD dampers on F1 cars, does anyone have an opinion on how the claims made for FSD (seperation of hub and body modes) apply to a race car?
  12. PTwizz

    Energy cost of manufacturing small car

    Star for Greg's link to google answers. Just the kind of data I was looking for. Thanks to all who have replied. SafetyDan; I was looking for practical justification to replace the Landrover, but I can't justify it economically (costs me about £700 per year to run, including fuel, insurance...
  13. PTwizz

    Energy cost of manufacturing small car

    Despite some time spent searching the web, I have been unable to find any figures for the cost, in terms of energy consumption, CO2 output etc, of manufacturing a new small car. The question arose out of a discussion in which it was suggested that I should replace my 1966 Landrover with a...
  14. PTwizz

    Thermodynamics of Stirling engines

    Thanks to all for the pointers. I have some ideas which fall into the general category of 'So simple someone would have done it if there wasn't something wrong with it.' Once I'm convinced I'm not going to make a fool of myself, I'll post details so you can shoot me down! Pete.
  15. PTwizz

    patented suspension

    I'm not sure what the design is supposed to offer. It seems all the claimed properties are available from a double wishbone setup with a little judiciois design and tuning. Pete.
  16. PTwizz

    Thermodynamics of Stirling engines

    Can anyone point me to a source of information on thermodynamics specific to Stirling engines, specifically heat transfer between sufaces and gasses? Thanks, Pete.
  17. PTwizz

    Gyroscopic coupling

    Phil, I would guess that steering linkage wear might not be related to mileage or other abuse. Driving my (non PAS) Landrover tells me that high steering loads occur at low speeds, i.e. when parking or tuning in a yard etc. Some trucks may do many highway miles with few low speed manouvers...
  18. PTwizz

    Gyroscopic coupling

    Smokey, I assume from your original query that this problem is not observed in new vehicles. Could it be that the geometry and stiffness issues which cause the problem are always present, but are masked by friction (in the steering linkages) on newer vehicles? Older motorcycles often used...
  19. PTwizz

    Alternator design

    Felix, I could fit a standard car alternator on the bike, but it is a custom project, and I would like to preserve the appearance of the original mag/dyno setup. The generator runs at approx 2X crankshaft speed, but the bike is a '53 Panther 600cc single, which doesn't do rpm! I am testing at...
  20. PTwizz

    Alternator design

    Felix, I am not too concerned about it being an alternator, so long as I can get the required power from the device. I was under the (possibly misguided) impression that an alternator was easier to control/regulate than a dynamo. I have been experimenting, turning the armature at 1000rpm, with...

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