I'd like to add my thanks for this excellent analysis. It solves a
problem I have been mulling over: How to safely jack up just the rear end
of the car. Insteead, I'm going to buy two more stands and jack the whole
thing, and put a tire under if need be.
At 08:08 PM 8/18/97 -0400, you wrote:
>If you are using decent jack stands, using four of them positioned well
>(toward the corners on the frame), and are doing it on a concrete floor,
>very little this side of a 7.6 quake will take it off the stands.
>Living here in Los Angeles, however, if I'm going to spend a good deal
>of time under the car, I take one last precaution if the wheels are off
>the car (dropping the car with no wheels on it could produce a severe
>case of "pancakism").
>Since the wheels are off the car anyway, just slide one of them under
>the car with you. If the car does drop, it will drop no lower than the
>width of the wheel/tire. While this probably would cause you some
>scrapes and bruises, there is no way the Triumph will flatten its own
>wheel and tire. If you wish to get very compulsive about this, just
>slide each tire under the frame at its corresponding corner of the car,
>or stack them two high--the car would not even touch you then.
>If you only use two jack stands, this is considerably more risky,
>especially if you do not block the wheels. The angle of the raised
>frame members in relation to the vertical jack stands is far from
>ideal. It clearly is possible to push a car off from two jack stands.
>If you have any of the wheels off, I would not want to get under it
>unless you had four jack stand placed well.
>To support your car, you should not use any masonry products (bricks,
>concrete blocks, etc.) as they can crack and bascially explode under the
>weight of the car, nor should you use wood (unless you have some
>reasonably new railroad ties--railroad ties are bulky, but as long as
>they are reasonably new, they are very safe as they have such a wide
>footprint, they are very hard to "tip the car off", are resilient, etc.)
>A short piece of 4x4 to distribute the load probably is safe as long as
>it is supported along its entire length (don't center a jackstand and
>span frame members with it).
>Never, never get under your car only supported by a jack, even if it is
>a good floor jack.
>Just buy a decent floor jack and use four jackstands. You can put a TR6
>in the air and on four jack stands in minutes. Used wisely, jack stands
>are very safe.
>Instead of being overly concerned about the car dropping on you,
>however, you should not be in the garage without dragging a small dry
>fire extinguisher out there with you if you are using a torch, doing any
>electrical work (i.e, the battery is still connected), using a welder, a
>grinding wheel on a drill or air grinder, or you are working in
>proximity of the fuel tank or lines, especially for any carberator work.
>I have seen more than one car catch fire e.g.:
>A backfire while adjusting double pumper Holleys--you would have to do
>one to know what I am describing here--toasted a 70 Z-28
>A loose fuel line bushing on a Fiat 124 Spider spewed gasoline until it
>filled the valley between the DOHC covers (an electric fuel pump) where
>it reached a dried out spark plug boot--burned it to the ground next to
>a gas pump at a filling station. This had everybody's attention.
>Old cars, old fuel lines, leaking gas, torches, frayed insulation on
>wires, backfires, and 12 gallons of gasoline--now that gets a little
>more scary than the jack-stand phobia.