double heading engines

[grandpabob]

I have received the new Santa Fe flyer HO set   I also have a older model bachmann engine.  both will run on the tracks at the same time but the older one is a bit faster.   will that arrangement over load the system?   
As a side question I have another engine that is older but the rudder tires are gone.  can I get new rubber rings for those tires?

[ACY]

It is best to stick to running speed matched locomotives in a consist. Call the service department regarding the side question, they should be able to help you get the parts you need.

[Jim Banner]

Reading the whole thread, I see: "One runs a bit faster than the other."  "The locomotives have to be speed matched."  These sort of statements beg the question: How much is "a bit?"  How close do the speeds need to be to be "speed matched?"  Let's put some numbers to it.

An oval of track on a 4 x 8 sheet of plywood has a circumference of about 20 feet.  If you run your two locomotives around such an oval with your older (faster) one in front, it is pretty easy to measure or at least estimate how much the faster locomotive pulls away from the slower one.  If they start off almost touching and after one lap around the oval they are one foot apart, then the faster one has traveled 1/20 or 5% farther than the slower one in that one lap.  Because they did this in the same time, the faster one is going 5% faster than the slower one.  If you do this test at various speeds and the worst difference in speed is 5%, you can say your locomotive are speed matched within 5%.  This is just fine for double heading.  Even if the speeds differ more than this, double heading may still be fine, but there is another test you might want to do.  If you use your older locomotive to pull a train that is typical for your layout, does it still run faster than your newer locomotive?  If not, then the locomotives will be okay to double head.  What will happen is the locomotives will share the load and neither will be pushing or pulling the other locomotive.

If you want to run two separate trains on your track, the above suggests a solution - put more cars behind the faster locomotive until the speeds of the trains match.

Now let's get back to your original question about whether or not running two locomotives will overload your system.  If you are using a train set power pack, then it might.  The power packs traditionally included with train sets generally produce enough power to run one train and light a few lights.  Such a power pack may not be able to handle two trains at once.  The only way to know for sure is to try it.  If you overload the power pack, the worst that normally happens is that the internal circuit breaker shuts off and everything quits running until the circuit breaker cools off and resets.  If this happens, you will probably want to upgrade your power pack or else limit your operation to one locomotive/train at a time.

Jim