Some temporary video of the testing, construction and parts breakdown of the part built simple 4 wheel equalized concept chassis.
Even though the parts are only placed loosely (almost/mostly
) together for the demo video, note the floor is completely stable in all simulated twisted track situations (and thus for rail bumps/dips). And the suspension is completely symmetrical for consistent dynamic wagon operation in both directions .
Hi Andy, hope your having a very good Thanksgiving. I presume you get the same buzz from that, that I tend to get out of Christmas.
For me Issue no. 1 is already, will the dining table be big enough on Christmas day.
Issue no. 2 was trying to get my head around your wagon suspension system, and what is happening at the wheel rail interface.
I see that it ensures you can maintain contact between wheel and rail for any reasonable degree of lack of flatness in the track, but only, it seems to me, because the 4 rocking points on the suspension (2 in mid W iron and 2 in mid sole-bar) are free to move away from the floor. Correct me if I'm wrong but I don't see how it can be otherwise. The floor will still sit firmly on three of the four giving you your firm ride (or will it, see below), but does weight distribution to the wheels vary depending on which of the three (or only if you are very lucky 4) rocking points are actually carrying the weight? Considering our worse case scenario of a sudden 0.5mm deep pit opening up under one wheel, the wheel will be free to drop into it but I had to wonder, what percentage of the wagons weight will it take with it?
I thought about that for a while as well.
The first thought was to wonder about that firm ride. Remembering that in our traditional 3 legged stool analogy, the stool is only really stable if the Centre of Gravity of the weight it is carrying is placed well within the triangle formed by the three points of contact (Russ's explanation/diagram from the CALG site here)
. When the floor is resting on only three pivot points, assuming that the wagons CofG is dead centre of the wagon floor (and probably some way above it), it will be on the very edge of the stability triangle which ever of the three points are involved, and so your wagon will be subject to a tendency to flip flop between the two. Not quite so firm then.
Next weight distribution. Having thought through the stability issue, the answer to the weight distribution issue comes from doing principle of moments calculations (I wont bore you), which show that, as the CofG is central on the line between two of the pivot points, all the weight will be carried equally by those two points, with none of it being carried by the third point. Mathematical proof, if any was necessary, of the tendency to flip flop between the two. The good thing from your point of view is that this turns out to mean that equal weight distribution on all four wheels is maintained.
Does the instability issue actually amount to anything? Almost certainly not on decently flat track. How rough track has to be before it begins to show, only experience will tell. Just lets remember that the only reason for indulging in suspension systems at all is because irregular track exists.
I did think briefly about putting springs under the sole bar pivot points, but then considering that your system contains as many moving parts and a lot more moving metal than a Bill Bedford style sprung wagon underframe (courtesy of CLAG again)
I wasn't convicted the game was worth the candle.
Enjoy your TurkeyEdited - P.S. On second read that was a genuine wish relating to real poultry meat, and not intended as any sort of comment about your underframe.