beam engine help

[Stephen GillParticipant @stephengill79322]

hi hope someone can advise me please i am building my first project a beam engine from scratch but it only works if i apply slight back pressure to one of the 5 mm exhaust ports any one know what i have done wrong ? regards steve

[SillyOldDufferModerator @sillyoldduffer]

First guess is the timing isn’t quite right – an adjustment.

Second guess is something physically wrong with the valve – dimension or fit.

Can you manage some photos?  Engine and plan.  There are several different ways of building a beam engine.

That it runs is very promising, can’t be horribly wrong.

Dave

 

[JasonBModerator @jasonb]

Most slide valve steam engines have one exhaust port not two, can you post a couple of pictures of the engine and portfaces.

is it your own design or a published one.

[JasonBModerator @jasonb]

Is it the large piston valve balanced one by Julius?

If so problems could be that the piston is not set to move equally either side of centre so one port is opening more than the other and also at a different time. Some adjustment of the eccentric rod length should even things up as he has not shown adjustment of the valve rod.

Also make sure you have the horizontal arm of the bell crank from eccentric rod to lifting links noveing equal amounts up and down a sthat too can alter the amout the ports get opened by.

[Stephen GillParticipant @stephengill79322]

hi its a piston spool valve have tried the timing every way make no difference can it be the eccentric crank offset is wrong ? but it runs quite well apart from needing some back pressure it is my own design so not sure how accurate the bore and stroke is but as a beginner i am learning a lot thanks for the help so far will post some photos tomorrow

[Stephen GillParticipant @stephengill79322]

hi connected the air this morning and it started working on its own but it still runs better with slight back pressure the alloy parts are only to help work out dimensions will be making new ones from these measurements the exhaust ports are 50 mm centres and it has 8 mm offset do you think these are about right ?

[JasonBModerator @jasonb]

In much the same way as I suggested in my earlier post make sure the valve is moving equally about the mid point. Saying that you can get it running better by covering one of the exhaust ports suggests that one is being opened more than the other. You should be able to do that easily enough with the two nuts. I’m assuming all passages are drilled symmetrically and the valve is also symmetric.

Also worth checking the piston leaves an equal gap at the top and bottom of it’s movement and that there is no restriction to the passages at the end of the cylinder due to cylinder cover spigots or being covered by the piston as this again could be causing a restricted flow from one end of the cylinder which you are then balancing by restricting the other.

As for sizes being right there are many other factors that come into it such as length of valve and the lengths of the full diameter and reduced diameter parts. But for the size of cylinder nothing looks out of place.

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