| Re: [GMCnet] Airbag loading question [message #127782] |
Sat, 28 May 2011 13:53 |
Gary Casey
Messages: 448
Registered: September 2009
Karma:
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Senior Member |
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I'm on the digest version of the list, so I'm usually a minute late and a dollar
short on these more fun questions. I think the question was, what is the load
on the bag (talking about the original design)? Assuming the bag lever arm is
the same as the wheel (it's not exactly, but it's easier to visualize that way)
and there is 2000 pounds of load on one wheel there will always be the same load
on the other. The bag will be supporting 4000 pounds of coach, but the force
the bag exerts will still be just 2,000 pounds, not the 4,000 as mentioned
below. If you drive quickly over a 4x4, there will be a difference in load
because of inertia effects, but it still holds true. Now if you drive slowly
over the 4x4, when one wheel is directly over the 4x4, that corner of the
vehicle will have a higher load on the suspension because of the weight it takes
off the other wheels, but that is a small effect relative to the overall weight.
The force exerted by the bag will still be close to 2,000 pounds.
Gary Casey
> Hi Bruce,
> Sometime back I asked if the right rear arm was the same as the left front
>(we're talking completely about the bogies here) - and the answer came back as
>yes, so I believe there's only 2 "parts" used for each bogie set and they're
>apparentely equal.
>
> Best as I can work out (doing this on the fly), if the mounting point of the
>airbag is the same distance from the center (those pesky bogie pins) as the
>wheel center is, each arm should be applying your 2000 pounds. That's 2000 each
>- forcing against the bag from each end so 4000 total 'in the bag'.
>
> If the distances were as mentioned, if you took out the airbag and stuffed in a
>scale of some sort (hungry man's bathroom scale?) :lol: and dropped the wheels
>to the ground, it should read 4000. If you put a jack directly under the center
>of one tire and lifted that single tire/wheel/bogie arm, letting its mate stay
>on the ground, the scale should still read pretty darn close to 4000 - there
>might be some changes as there's angles to consider versus the two pivot points
>(the two bogie pins), but I don't think they would amount to great values.
>
> I think that's it...then again, it's early. ;) ?Oh, if the airbag mounting
>point is of a different length than the axle center to bogie pin distance,
>there's math required for the leverage (or lack of) the axle has over the airbag
>mounting point.
>
> It's still raining or I'd go measure but I have a feeling the leverage point of
>the bag is less than the axle distance, so that means 2K at the axle might mean
>(guessing) 2200 at the bag, then x 2 = 4400. If it's more, it might mean
>(guessing) 1800 at the bag ( x 2 = 3600#).
>
> Gord :)
>
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