Brooks Locomotive Works was building many engines with "extended piston rods" from around 1890 into the early 20th century. Can someone tell me the purpose of this feature? Thanks.
Tim Guenther
Extended Piston Rod
Re: Extended Piston Rod
Please define "extended piston rod".
If it refers to the piston rods sticking out the front of the cylinders in a sealed sleeve, there are several reasons for those.
1) Bearing support for the front of the piston and rod, giving longer lifetime of the cylinder bore. No gravity pulling the piston and rod down.
I've rebored full sized locomotive cylinders that had become oval due to this wear.
2) To produce equal thrust on each side of the piston. The volume of the piston rod makes a difference.
The result is equal thrust both forward and backward, and a better balanced locomotive under load.
Anyone have other input on this?
RussN
If it refers to the piston rods sticking out the front of the cylinders in a sealed sleeve, there are several reasons for those.
1) Bearing support for the front of the piston and rod, giving longer lifetime of the cylinder bore. No gravity pulling the piston and rod down.
I've rebored full sized locomotive cylinders that had become oval due to this wear.
2) To produce equal thrust on each side of the piston. The volume of the piston rod makes a difference.
The result is equal thrust both forward and backward, and a better balanced locomotive under load.
Anyone have other input on this?
RussN
Re: Extended Piston Rod
Any slack in the crosshead would translate in to rocking motion of the piston (and there's pretty much endless talk about how loose a loco must be to operate). I strongly suspect the extended rod was to help offset that force.
I'm not convinced gravity played a huge role in the eccentric wear, as it simply isn't that great of a force, very unlike the force of the piston rod pushing the connecting rod. Could be wrong, though!
H
I'm not convinced gravity played a huge role in the eccentric wear, as it simply isn't that great of a force, very unlike the force of the piston rod pushing the connecting rod. Could be wrong, though!
H
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K. Browers
- Posts: 94
- Joined: Wed Mar 21, 2007 11:57 am
- Location: Philippines
Re: Extended Piston Rod
Hello everyone.
Extended Piston rods were very common in Europe and also stationary engines. The front of the piston did have a bushing that supported the extended piston rod. I just did a quick back of the envelope calculation of a 20 inch piston and it would weigh in the neighborhood of 175 lbs that would be a lot of weight to suspend from the cross head and a bushing in the rear cylinder head only this would eventually lead to wear on the cross head slippers the piston head bushing and the bottom of the cylinder. A engine with 45 inch drivers would make 3,500,000 revolutions in traveling 30,000 miles. What is amazing to me is that such simple machines could do so much work even when mostly worn out.
Cheers
Karel
Extended Piston rods were very common in Europe and also stationary engines. The front of the piston did have a bushing that supported the extended piston rod. I just did a quick back of the envelope calculation of a 20 inch piston and it would weigh in the neighborhood of 175 lbs that would be a lot of weight to suspend from the cross head and a bushing in the rear cylinder head only this would eventually lead to wear on the cross head slippers the piston head bushing and the bottom of the cylinder. A engine with 45 inch drivers would make 3,500,000 revolutions in traveling 30,000 miles. What is amazing to me is that such simple machines could do so much work even when mostly worn out.
Cheers
Karel
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Mark Landgraf
- Posts: 100
- Joined: Sun Jun 09, 2013 9:42 pm
- Location: Albany, NY
Re: Extended Piston Rod
Hi,
In the late 1800's, certainly the above reasons were accurate, but the extended piston rod could/was also used to pump water on it's forward stroke into the sealed sleeve. I believe that B&O used this technology.
Mark Landgraf
Albany NY
In the late 1800's, certainly the above reasons were accurate, but the extended piston rod could/was also used to pump water on it's forward stroke into the sealed sleeve. I believe that B&O used this technology.
Mark Landgraf
Albany NY