I have a 85 ft track layout about 1.4 scale miles and I only have one transformer no DCC just a transformer. I wanted to run two complete trains equally spaced apart on my layout. I have a bachmann B23 and an Ahtearn Ac4400 both ho scale and don’t want to damage either. Just wanted to make sure that this will work and not cause any damage to either locomotive. Thanks
It will work, yes, but you’ll have no way to control them independently. Start one, they both start. Stop one, they both stop. And one will eventually catch the other.
Yes, for a short time.
You will not be able to independently control the speed of each loco so the faster will eventually catch up with the slower. (This might happen quickly or slowly). You can adjust the time somewhat by adding or subtracting cars but it will never be perfect.
If the locos are perfectly speed matched you can also run them in a “consist” (multiple locomotives pulling or pushing one train). You don’t want them pulling or pushing each other.
Having some blocks that can be switched on and off will allow you to pause the following train while the leading one gains some ground, but all in all it’s not the most practical way to run a railroad. Two controllers with block zones would be better and many here will tell you to go with DCC (I have not yet but plan to “some day”). My double track main is 125 feet long and I sometimes let one train run in a loop while using part of the main for switching maneuvers. Two controllers though. Timing is critical too.
You won’t damage the locos unless they crash.
PS: 
The question is, will you damage the transformer. You don’t mention what model and make transformer you have. They all run on 120V INPUT, however the secondary windings of the transformer will determine the output that the transformer can provide.
Each locomotive that you add to your tracks adds another resistive load upon the transformer. Look at the spec plate on the transformer to see what the output current ( amps ) is. Each locomotive motor will be another load in parallel. The voltage will remain the same but the current will be approximately 1/2 for two locomotives, 1/3 for three locotives, etc.
It is also dependant on just how much power each is using. (a factor of the engine itself and the number of cars each pulls, any grades they must tackle, etc). You can hook up an ammeter to see what is going on. Sometimes it’s not that it cannot be done, but that you have a sick little loco.
One way you can get some control is to put in “blocks” to cut the power to sections of track. that way, if a train starts to catch up to the other one, you can throw a toggle switch and shut a train down so the other one can get ahead further down the track before repowering the locomotive. It required 2 power packs but what was called “Cab Control” was sort of the way we did it before the DCC days. It will work with one power pack but two are recommended. All you have to do is insulate a section of track between two points in one side of rail then take a lead wire from the transformer to an on/off toggle switch then wire it to the track between the insulated track sections. Common rail wiring for block control is the simplest way to wire for blocks but the drawback is that a lot of accessory equipment won’t work with common rail wiring. It would be a quick fix until you get a 2 power pack Cab control system or a DCC system in it’s place…chuck
There’s a very simple way to find out – just do it. If one runs a lot faster than the other, no damage will be caused to the locomotives as long as you don’t let them crash.