Impact load between loco and bogie?

[barrind]

We need to measure the impact load between a loco and a bogie during a normal shunting operation. Its been a long time since I had to think about anything like this, I was thinking about placing accelerometers on the loco and bogie to measure the peak longnitudinal g, assuming a straight shunt, then using that to determine the force. What would be the equation to use? Is it as simple as force=mass x acceleration, or is it function of the time of impact? Like I say, its been a long time, need the old brain kickstarting on this one.

 

[MintJulep]

Difficult to do with accelerometers due to the amount of free play typical in the connections between the loco and the truck. In theroy the force could be determined as the peak DIFFERENCE between F=ma for truck and F=ma for loco. The problem is at some times m would be only the truck or the loco, and at other times it would be the sum.

Consider strain gauges on the bolster and/or king-pin and whatever other connections your configuration may have.

 

[barrind]

Thanks for that. It turns out the customer only wants to know the maximum acceleration the loco side sees during a typical shifts operation to compare with figures they have from other normal shunting operations. So hopefully a simple series of logged peak g events will satisfy.

 

[unclesyd]

I used a readily available commercial device that records any loads imposed, normally hidden in a freight package, on the switch engines to get some data on our two switch engines. The first two devices that we tried were over ranged and it took a special to get any data.
Our engines were the small double ended type with the cab in the middle powered by 671 Detroit Diesel's. We found out that our contract yard teams were cowboys on the dark shifts.

They had broken the "bolsters", bent the king pins, tore the plate that king pin attaches to, and wrecked several couplings, beside jumping the track.

 

[unclesyd]

Here is a very similar instrument to the one we used and in the fog of my mind it could be the same one.

http://www.shockwatch.com/

 

[amorrison]

Surely the answer to this question is trivia to railway engineers who design railcars/diesels etc!

Railroad engineering reference manuals or call a railcar manufacturer.

 

[barrind]

In this case it is a railcar manufacturer asking for the information in order to design locos for our site. The locos are to be used on a steelworks, not a main branch line and the designers want to know what the real life duty is going to be. They have only asked for the peak acceleration so we assume they will have the expertise to calculate the loads as you say.