Strange running?

Ive just had my 71/4 Invicta running on air. Pipe air to just left cylinder and it runs fast and smooth, pipe air to just right cylinder and it runs fast and smooth, pipe air to both and it neither runs smooth nor fast. The only thing linking the two 'sides' is the front axle. I realise that with both sides running it is using twice as much air, and so only half the volume is availible to each cylinder but there should be the same amount of power produced?

sound like valve timing to me.

I had to have a look at someones valve setting on a Royal Scott. he had 2 cylinders going one way and the central cylinder wanted to go the other way. each ran smoothly when piped up individually.

By dividing the air supply between 2 cylinders you have halved the potential volume to each, and you have also reduced the pressure to each. Thus it will not run correctly. Power is a function of work done (force x distance moved) divided by time taken.. As you can see you have reduced the force, and so reduced the distance it travels and also as a result increased the time element. So your engine will in fact produce greatly reduced power output. Simples. May the "force" be with you.

The valve cuts off admission part way down the stroke and air cannot be used 'expansively' in the same way as steam.

I have a three cylinder marine engine that runs very jerkily on air but absolutely fine on steam.

thanks all...thats what i thought. valve timing is spot on. just need some coupled wheels now!