Stuart victoria

Hi all

I have just got to the stage of doing a trial assembly of the engine (photos to follow) and have come across a big problem.

On the out stroke the slide bearings hit the back posts and on the instroke the bearings are 7/16 off the front posts and the piston is the same distance short of its "full" return position.

Its almost like the con rod is 3/8 short between centers.

I have double checked my dimensions and they are spot on

My question is would the engine stroke under pressure with the piston not getting back to the end of the cylinder.

Thanks in advance

Art

It sounds as if your diagnosis of the the con rod centres being too small is correct.

Effectively the piston and cross head need to be moved forward, relative to the Crankshaft bearing saddles.. To my mind, the distance should be such that if the engine is double acting, the clearance at inner and outer dead centres should be equal.

To avoid damage, I certainly would not apply air, or steam, pressure until the situation has been rectified

But I am not a steam man, so others may give different advice.

Howard

Edited By Howard Lewis on 06/02/2021 12:52:15

[This posting has been removed]

Hello Arthur,

Given that the cross head slide bars are at their correct location and I'm sure they are then the issue has to be either the conrod or the piston rod length. As previously said at mid piston stoke the cross head should be equally spaced between the ends of the cross slide. (The crank will not be vertical at this point)

I would look at the piston rod length between C/L of piston width and C/L of cross head pin again as I think this is where your problem may lay

Regards - Tug

Hi

Thanks for your advice. Will look at tugs suggestion.

Have been unable to upload any pics. Keep getting "memory low" error.

Does anybody know what the max resolution/ file size is.

Thanks again

As I see it given that the crank bearings and the slide bar mountings are located on the engine bedplate and thus likely to be correctly positioned, then the crosshead should not impact the slide bar posts if the conrod is the correct length regardless of the piston position. Disconnecting the piston rod from the crosshead would eliminate it, or not, from the equation.

Jim

[This posting has been removed]

Hi

Thanks for your advice. Will look at tugs suggestion.

Have been unable to upload any pics. Keep getting "memory low" error.

Does anybody know what the max resolution/ file size is.

Thanks again

Gosh, you're quick on the draw this afternoon br!

Art may not have responded (yet), but I'm sure others would have taken note! Don't forget forum threads are read by many interested people, most of whom never comment.

Dave

[This posting has been removed]

No limit on what you can upload as forum software will resize it but must be a .jpg image file.

Agree with Dave, some people are not just sitting in front of their screen and may take a while to read a reply, if OP said his sizes on the drawing are correct I doubt posting yours presumably from the drawing would have helped anyway.

As said by others check piston rod/piston/crosshead assembly to make sure that is not overlength but if it's hitting the posts rather than hitting the end of the cylinder sounds like something else.

[This posting has been removed]

Loading a big photo into a forum album automatically reduces it to 1024x768 pixels (I think), but the process is prone to misbehave if you have a big image and a slow internet connection or the server is busy.

When I had an 8Mb/s link it was worth reducing photos at my end with an image editor to 1024x768, but I've not bothered since upgrading to 40Mb/s. However, for taking internet pictures I set the camera to low or medium resolution, because small pictures are less likely to cause trouble. At high resolution my SLR camera creates gigantic jpegs, and I'm not sure this poor old forum could suck them up without gagging.

Dave

Just looked at the two sets of drawings that I have, the older ones have the conrod ctrs at 6 1/32" and the newer ones at 6 1/4,

Horizontal distance between crankshaft ctr and ctr of guide bars is also 6 1/32" so would suggest the older sizes are correct and the new ones not

[This posting has been removed]

Don't let the lack of obvious approval put you off - I think most forum contributions drop silently into the pool!

I'm guilty too - I often see marvellous photos, smart ideas and clever techniques without commenting. I get more out of the forum than I put in, and it's thanks to blokes like you. Keep up the good work! I'm reading your posts...

Dave

Hi thanks to all

Re jasons post. As i said my con rod centers are 61/32 bu my crankshaft to center of guidebars is just over at 63/64 not enough to creste my problem.

Im thinking the pads on my baseplate are out and will speak to stuarts tomo sbout it.

Once again thanks to all

Edited By Arthur Goodwin on 06/02/2021 14:45:14

Looking at your photos I feel that your con rod is short. I fail to see how the pads on the base casting can be wrong

Roy

From the photos it appears the con rod is short. Noel.