The Unofficial Mamod and Other Steam Forum

Graham-Jilly · Posted: Tue Jun 19, 2007 11:42 am Post subject: SE3 timing

what is the correct position for the pistons on an SE3
mine seems out of wack a bit doesnt perform as good as i think it should

also have another which has the pistons loosened so needs retiming as well
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MTA · Posted: Tue Jun 19, 2007 11:46 am Post subject:

For a two cylinder engine, set the cranks at 90 degrees to each other

So one is pointing upwards, and the other set at 90 degrees left or right to that

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"If the fascination engendered by locomotion at the present day is so intense, the attractive powers of locomotion in miniature must of necessity be greater still"

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Graham-Jilly · Posted: Tue Jun 19, 2007 11:48 am Post subject:

thanks MTA thats why it isnt running too well it they are set at 180 apart
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Mamodman123 · Posted: Tue Jun 19, 2007 12:01 pm Post subject:

Nooooo

Just off 180 G+J!
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Chris · Posted: Tue Jun 19, 2007 12:06 pm Post subject:

It is 90 degrees for double acting pistons (like on the mamod locos). I thought it was 180 degrees for single acting ones like on the SE3.

I also thought that setting them slightly out of 180 improved the running.

MM will know anyway.
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Chris · Posted: Tue Jun 19, 2007 12:07 pm Post subject:

MM posted at the same time as me.
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Mamodman123 · Posted: Tue Jun 19, 2007 12:09 pm Post subject:

Yep just off 180 then they go like stink

Has anyone tried it at 90?

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Chris · Posted: Tue Jun 19, 2007 12:11 pm Post subject:

Would have thought it wouldn't run very smooth at 90. You would get two pushes close together followed by a longer pause, then two pushes close together.

If it is easy to do give it a go and see what happens.

Or send me an SE3 and I will try for you.

Always happy to help you see.

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MTA · Posted: Tue Jun 19, 2007 12:26 pm Post subject:

Obviously full size practice doesn't work on models then

Try both and see which is better

_________________
Si

"If the fascination engendered by locomotion at the present day is so intense, the attractive powers of locomotion in miniature must of necessity be greater still"

W.J. Bassett-Lowke. August 1911

Mamodman123 · Posted: Tue Jun 19, 2007 12:28 pm Post subject:

Chris · Posted: Tue Jun 19, 2007 12:39 pm Post subject:

I think it is all just down to whether they are single or double acting.

I'm not very good at explaining. Roly has a go at it in his booklet, so you could read about it there.

Other than that here goes...

A single acting double piston engine would have two strokes per rotation of the flywheel (one stroke being the piston being pushed out of the cylinder). So the smoothest action would be for the pistons to be at 180 degrees. That way the flywheel is getting a push at each half turn. (piston 1 pushes, piston 2 pushes, piston 1 pushes etc).

A double acting double piston engine would have four strokes per rotation of the flywheel so the smoothest action would be for the pistons to be at 90 degrees. (piston 1 pushes, piston 2 pushes, piston 1 pulls, piston 2 pulls, piston 1 pushes etc).

The above description by me is why Roly has written a book, and I couldn't!!
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Mamodman123 · Posted: Tue Jun 19, 2007 12:41 pm Post subject:

Chris · Posted: Tue Jun 19, 2007 12:42 pm Post subject:

Mamodman123 · Posted: Tue Jun 19, 2007 12:44 pm Post subject:

Graham-Jilly · Posted: Tue Jun 19, 2007 8:27 pm Post subject:

Thanks everyone for your help will give it a try
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