The Steamboating Forum

Hard-chromed piston and valve rods, u-cup seals made of viton or some other fancy-schmancy aerospace elastomer, and finally a small line running from each gland to condenser vacuum. If there is a leak, any discharge is pulled into the condenser... pulling it apart to replace the seal is a PITA though, as you have to separate the stems from their crossheads/yolks, and re-assemble with a depth-micrometer to ensure duplication of the original setting. Done it once so far in 10 years of ownership. Never a drop, even when the seals needed replacing.

Thanks for all the thoughts guys. Wes, I've sent you a pm asking for more details....
Cheers,
Daniel

Mike Rometer wrote:I've used solid PTFE bored and turned to a good fit as gland packing. Haven't proved the longevity to my own satisfaction yet, they haven't been run enough yet, but they work well.

Works without compressibility? How many thousandths is a "good fit".
I have a 6a and the pump leaks out the shaft. I have repacked... at least 5 times and I cannot get it to stop. I was thinking. There is an inherent problem having a shaft motivated by an eccentric and having no cross slide (nothing to linearize the shaft movement). So there is considerable vertical force on the packing. I have considered increasing the length of the "aligning" bushing. I wouldn't mind the leak, but it spills into the engine sump where it mixes with nasty oily crap and causes flooding. I have to pump it out pretty often to keep the flywheel from throwing it all over me.

wsmcycle, your problem is that the side force from alternate directions is making channels along the side of the pump rod in the packing. You can either improve the bearing (best choice), or make a packing that will handle side motion.

One way of doing that is to make a series of alternating PFTE washers, one sized to be a close fit over the pump rod and a ample loose fit in the bore, and the other a tight fit in the bore and a loose fit on the shaft. Compress these and you should get a handle on the leak.

- Bart

Bart. That kind of agrees with my thinking except this wobble would be vertical not side to side. Maybe there is something mysterious here that i am missing but on the 6a the piston/shaft moves on the eccentric perpendicular to the axis of the engine. However, either way, side to side or top to bottom, the tighter/closer fitting bushing will reduce the beating which the packing is enduring.

Thanks

wsmcycle wrote:

Mike Rometer wrote:I've used solid PTFE bored and turned to a good fit as gland packing. Haven't proved the longevity to my own satisfaction yet, they haven't been run enough yet, but they work well.

Works without compressibility? How many thousandths is a "good fit".
I have a 6a and the pump leaks out the shaft. I have repacked... at least 5 times and I cannot get it to stop. I was thinking. There is an inherent problem having a shaft motivated by an eccentric and having no cross slide (nothing to linearize the shaft movement). So there is considerable vertical force on the packing. I have considered increasing the length of the "aligning" bushing. I wouldn't mind the leak, but it spills into the engine sump where it mixes with nasty oily crap and causes flooding. I have to pump it out pretty often to keep the flywheel from throwing it all over me.

It's a soft material so as close as you can get. It compresses with tightening the gland and expands outwards as well as inwards.

I have 'O' rings on the valve gear with long guide bushes either side, they seem to last well. (The 'O' rings that is!)

6A engines have an angularity issue there especially on the H.P. valve rod. Just too short of an engine design.

It can help to replace the 5/16" valve rod with a 3/8" one.

Getting the side to side forces and movements under control will almost certainly make the life of the packing much easier.

Sorry all!
My leaking is from the water pump! Not the piston rods. I see now why you said "side to side" movement (my wobble is vertical). I made a new closer tolerance bushing/packing compressor yesterday. I am anxious to try it out. It is going to rain all day here in Arkansas or I would already be on the river. I may run on compressed air inside the plant. I can hook up a bucket of water to the infeed of the pump and push it into the boiler at 100#s. This stationary running will allow me better scrutiny of the offending gland.

wsmcycle wrote:Sorry all!
This stationary running will allow me better scrutiny of the offending gland.

I often find that going to a dock where I can run the plant while being tied up lets me debug a lot of little issues.. I also find a smart phone handy to film what is happening in places I cannot put my head.

- Bart

Bart, I'm not even going there on places you cannot put your head.