Center of Gravity Location

[Bruce VoelkerdingParticipant @brucevoelkerding91659]

Here is a Method (I have not actually tried it) to determine the Location of the Center of Gravity from the Front Buffer Beam using only a Simple Lever. I have not applied Error Analysis to it to see the Effects of Measurement Errors. I imagine the mathematical leaning Fellows on the Forum may appreciate this Thought Exercise.

The Term "Summing the Moments" was pounded into our Heads at University.

[Bruce VoelkerdingParticipant @brucevoelkerding91659]

[Speedy Builder5Participant @speedybuilder5]

I can't comment on your calculations, but I think you have found the centre of balance. The CG could be anywhere between the rail head(unlikely) or the top of the funnel and at the point you have calculated. Again, is the Loco boiler empty or full ? or perhaps I am on the wrong tracks !

Bob

[Martin ConnellyParticipant @martinconnelly55370]

I used to do this type of thing but without the beam underneath. We lifted a large load at one set of lifting points at one end just enough to get it to rotate and recorded the weight from the crane and the distance from the fulcrum point to the lifting point. Then repeat with a set of lifting points at the other end and also record the distance between lifting points. Off hand I can't recall if the known total weight was included in the calculations but I think not, we had a program on a programable calculator to calculate the distance to the CoG from one of the lifting points and marked it on the load. We also, very occasionally used four load cells under a load to calculate the vertical height to the CoG. This required lifting one end of the load about 300mm higher than the other and recording the weight at each load cell and the distances between the load cells. Then repeat with the other end raised higher by the same amount. With the two calculated CoGs you could do a scale drawing and where the two lines of CoG crossed showed how high it was. I've probably still got all the relevant PC files somewhere.

An added extra to the program on the calculator was that it could be used to work out the number of links required for the spreader beam chains to get a correctly balanced load with the first lift and also if any leg on the lift was exceeding its WLL

Martin C

Edited By Martin Connelly on 07/01/2023 16:27:19

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Bruce, I agree with Bob, that you have found the centre of balance, as it doesn't tell you if one side of the engine is heavier that the other, which will shift the C of G sideways towards the heavier side, whereas Martins example on four separate load cells and the height calculations should.

Regards Nick.

[noel shelleyParticipant @noelshelley55608]

Boiler full, side tanks full, bunker full ? Or a bare Loco. Put loco on just enough ali rail to stand, sit it on top of a piece of round bar and roll untill balance point is found ? Noel

[Tim StevensParticipant @timstevens64731]

Yes, this is a way to find how far the C of G is from the front of the Locomotive. But it does not fully locate the C of G, as you also need to know the height and whether it is bang on the centre line or how far to which side. And the figures will all change when fuel or water is added or used. The device which measures the applied load needs to be zero-ed, and it helps to fix a fulcrum below the beam so that no errors can be added when the relative positions are changed (but I expect you knew that).

The C ofG position will also change whenever the locomotive accelerates or slows down, and also when it is on a gradient up or down, or going round a bend, because of the effect these changes have on the fluid levels and fuel position, so there is very little benefit from a calculation to three places of decimals.

Hope this helps

Regards, Tim

[Nicholas FarrParticipant @nicholasfarr14254]

Ni Noel, I like your method, might be a bit of a challenge with a full size standard gauge engine though.

Regards Nick.

[Author]

Posts