The Home Machinist!

To follow up on another post I finally completed the modifications to the K4 spring rigging

This modification most centered around the lead truck.

When entering a turn the lead truck not only turns but lifts the front end using the swing links to make up any difference in the distance to the pivot that is located on the frame under the cylinders.

After consulting with my friend Dan Horting who is building a modified version of my design I came to the conclusion that the 1361 lead truck was too stiff.

The leaf springs were stiff. Dan used some phosphorus bronze spring material to make his spring. He gave some of this and I used to make the new spring.

Further the attachment points to the equalizer did not give at all therefore making the truck stiff with no movement .

This stiff action would lift the frame in turns giving less weight on the drivers and causing slippage.

I tested the K4 last Sunday. There was a marked difference.
Now with a fully loaded five car passenger train there was no slippage in the turns.

https://www.youtube.com/watch?v=1-8eoCrobjY

Unless your equalization on the drivers and trailing truck isn't working, the vertical lift on the lead truck will not change ANY of the load else where on the engine. If you think you are slipping because of this, I would check the trailing truck equalizer to make sure its travel is not bottoming out or being inhibited in some way.

Springs take out the shock of a bump or dip, they don't change the load.

JP

Hi John

I disagree with that at least for my locomotive. The lead truck spring was so stiff the it indeed would lift the front of the locomotive and lighten the load on the front driver. The slippage would only happen when in a turn.

I also noticed it when backing onto the transfer table the weight of the locomotive would stretch the lifting chains and the lead truck would hang up lifting the drivers off the rail. With the new changes this did not happen.

I can not speak to all locomotives but on the 12" to the foot types on at least the 4-8-4, I know the lead truck is suppose to take weight off of the front drivers to minimize wear to the flanges in curves. When the Up brought the 4014 back one of the crew had set up flange oilers, he took a lot of flack from the armchair RRers but when you have to turn drive wheels, there are maybe more things you want to do. So its a trade off.

Oh dave another great video!

My 3 cents worth

johnpenn74 wrote:.....
Springs take out the shock of a bump or dip, they don't change the load.
JP

Sorry, if you adjust a spring hanger nut you introduce an extra vertical load which affects all the other ones. Textbooks on locomotive design are full of the proper theory and the way to work with it.
Kind regards
Jos Koopmans

JJG Koopmans wrote:

johnpenn74 wrote:.....
Springs take out the shock of a bump or dip, they don't change the load.
JP

Sorry, if you adjust a spring hanger nut you introduce an extra vertical load which affects all the other ones.

That's jack screws and spring wedges are two ways handling adjustments are made in NASCAR.

johnpenn74 wrote:.....Springs take out the shock of a bump or dip, they don't change the load.

JJG Koopmans wrote:Sorry, if you adjust a spring hanger nut you introduce an extra vertical load which affects all the other ones.

Pre-loading springs one way handling adjustments are made in NASCAR. It's called a wedge adjustment and is done with a long socket extension through the back glass (lexan) during pit stops.

Wait a second guys, Preloading is done captively, That is, when you preload you physically shorten the travel range of the spring (usually coil) so that is only works in the specific range of deflection. This does not change the load that the spring takes. It does not increase weight out of thin air. It simple forces you into a range of spring response that is takes and returns a higher force. If you tighten the spring preload all the way down then you are riding on a solid block of steel, that is a completely inelastic response. The weight on the wheel didn't go anywhere.

Take for example my off road bike. If I completely tighten my forks down they become extremely rigid when I hit bumps. BUT the weight on my front wheel didn't go anywhere; the bike's center of gravity didn't change. The front wheel loading is exactly the same as it was. This is an example of when your steam engine has springs that are TOO stiff. Suspension being too stiff makes you slip. But there is no magical transfer of weight. If you go the other way and have to soft a spring then you end up bottoming out or topping out the boxes, lever arms, equalizers, etc. which has the same effect as being to stiff.

I don't know where the myth about a lead truck shifting load to drivers in a curve and will challenge anyone to find any railroad cyclopedia or design document that supports this. It is a farce and can be disproved with basic freshman Statics equations. In short, unless the center of mass of the engine moves, or the length of the equalizer or fulcrum point changes, the load isn't going to change. Springs don't change the load, springs absorb the momentary impulse, the load is always constant.

JP

johnpenn74 wrote:..... Springs don't change the load, springs absorb the momentary impulse, the load is always constant.
JP

Of course they don't. Spring adjustment changes the load distribution
kind regards
Jos Koopmans

johnpenn74 wrote:Springs don't change the load, springs absorb the momentary impulse, the load is always constant.

On your bike, there is no left / right distribution.

On a car, if you increase the spring rate in one corner, you add weight to that corner and the diagonally opposite corner, and remove it from the other two corners. The TOTAL stays the same, but the distribution changes.

Steve

For once I agree with Mr Koopmans

The weight of the locomotive remains the same it is just distributed differently.

I now have more weight on the drive wheels . That's where I want the weight.

The 1361 now pulls like a farm tractor. BIG difference.

Hey Dave,
Are you doing to bring this tractor to different fields (meets) to show us or do we have to go to your barn (PLS) to see it?