Dave I think that if you look at your bogies you will see that they are
configured differently than your diagram. the pins on one end and the wheel
on the opposite end with the bag in the middle on a fulcrum. the force on
the wheel is composed of two components, one vertical and one horizontal. I
haven't done the calculations but believe that the force on each wheel
equals the force on the end of the bag.
It looks like the new diagram I tried to draw:
>
> >> the total force on the cone is
> >> 1/2 the force in the bag, since that force is
> >> applied to 2 arms, and thence
> >> to a 2 wheels.
> >That's what I thought I said. ("..whatever force the cone is trying to
> >transfer to the bogie
arm.") Sorry if I was unclear.
>
>Actually the force on each cone is equal to the force on the bag. I have
>not measured the ratios of the arm lengths (bag arm vs. wheel arm) but I
>would guess that its pretty close to a two-to-one ratio. If that is the
>case then the force on each of the cones is twice the weight on each wheel.
>Here is a little schematic (I hope it survives the e-mail process) and a
>few of the force relationships.
>
> /----------\
> / \
>Front Cone Force --|-----------( Bag )----- -- + | \ / |
> Bag Arm --| \----------/ | | | |
> +--------+---------+ +------+-----------+
> ^ ^ ^ ^
> | | | |
> | --------- Wheel Arms ---------- |
> | |
> Front Wheel Rear Wheel
>
> 1) Cone force = ratio of the arm lengths
> (Wheel Arm / Bag Arm) times the weight
> on the wheel.
>
> 2) Cone force = Air pressure (in PSI) times
> the effective piston area (in square inches)
> of the bag.
>
> 3) All Front forces = All Rear forces
>
>As you can see, the forces on the cones are quite high. A (very) rough
>guess is that they are in the range of 4000-5000 lbs at 100psi.
>
>I have a 73 Sequoia and did not experience the exploding cone problem. I
>replaced the bags a few years back as a preventative maintenance measure. I
>did not know about the exploding cone problem at the time but I did replace
>the cones when I replaced the bags. After hearing the horror stories about
>exploding cones I am glad that I did.
>
>I would be curious to see if this or other safety related problems have
>shown up in the NTSB records. I do not know if/how the NTSB collects
>information for non-aviation vehicles. I assume they do collect this
>information and am reasonably sure that there are some records on file
>related to the GMC's. I base this assumption on the fact that there is a
>rear brake/bearing failure related recall of the earlier coaches. I have
>always been curious if there are other incidents recorded at the NTSB that
>did not prompt recalls.
>
>My experience (related to aviation) is that the data collected by the NTSB
>can be a very valuable source of hard facts related to potential safety
>problems. Knowing what kinds of failures have happened in the real world
>can be quite useful in drawing ones attention to the areas that need to be
>looked at during preventative maintenance.
>
>Actually, this could be a good on-line project. The net is a great resource
>for collecting (and collating) information directly from people who have
>had first hand experience. How would you guys feel about posting specific
>information regarding safety (or even operational) related incidents to an
>on-line database?
>
>I know that there is a lot of hear-say and anecdotal information out there.
>Some of it quite useful. Unfortunately the more spectacular failures tend
>to get a lot more attention through the grapevine than the (maybe more
>common) run of the mill failures.
>
>If we had a database that had actual incidents recorded along with
>specifics (like VIN's, year, mileage, manufacturers part numbers etc) we
>could find out if we are hearing multiple repetitions of a rare (albeit
>spectacular) problem or if the problem is something that we should really
>be loosing sleep over.
>
>Maybe this data could also provide us each with enough real world
>information to look for problems and take steps to prevent those problems
>before they actually happen to us. I can see this being especially useful
>as our classics become older and begin having more end of life related
>failures such as metal fatigue, chafed wiring, hose or pipe failures etc.
>
>Maybe this idea is overkill. But the idea is based on what is done in the
>aviation world. Every safety related failure is recorded and the data is
>used by manufacturers, government, owners and operators to look for
>patterns and problem areas that could effect them. The big difference is
>that the aviation business is highly regulated and reporting is mandatory.
>That makes the data quite accurate and pretty reliable.
>
>But there is a good possibility that a voluntary database would be valuable
>if the information in it was specific and traceable (via VIN numbers).
>
>Just some food for thought.....
>
>Dave
>73 Sequoia.
>
>
>
Tom & Marg Warner
Vernon Center NY
1976 palmbeach
wner-gmcmotorhome]On Behalf Of Dave
