What is this?

[wsmcycle]

I don't have a condenser on L'ill steamy so I previously ran my 6A on her without even the feed water pump. Now that I have determined (via the forum) that i need a mechanical feed water pump, I am going to pursue the completion of my 6A. I do not know (though i can guess) what this pump is? I don't have all of the castings for it (i bought it a few years ago on ebay) but I think it is a vacuum pump. Is that right?
I hope you guys don't tire of me. I am sincere and I will complete this 6A. I don't think i need to be concerned with this "vacuum" pump but only the feed water pump on the other end.
I had my engine in L'ill steamy a few years ago and I wrote up an unbelievable account of the disasters of the first outing. I replaced it with the original Semple engine because i felt that i didn't have enough operating pressure to fully appreciate the compound design. (how much would I need?) I have since slowed down and i am resolved to travel at whatever speed will keep the boiler >80#s. I am a speed demon. 7 is better than 6 and it's a long way from Fort Smith, AR to the Mississippi river (my goal). It is down stream however and I could make it on a raft.

[gondolier88]

That would be the air pump- you correctly allude to it's use as the vacuum pump and maintains circulation in the condensing system.

I didn't see the posts regarding the water pump being necessary, but one BIG recommendation regarding the 6A boiler feedpump- try and run it at 1/3rd engine speed- so 3rpm on the engine would be one pump. The internal waterways in the design are quite restrictive and driven at cruising speed or higher almost always make a real racket as cavitation occurs and the check valves bang back onto the seats without water to stop them. A 3:1 nylon reduction gear in lieu of the eccentric makes for a far quieter and reliable pump.

Greg

[wsmcycle]

What would this reduction gear look like? How do you replace a cam with a gear? I don't get it.
Can you reference a pic or two somewhere? Help?

[Mike Cole]

I have a direct drive water/pump driven the same as this one. As the engine is a ST 5a then the revs are high. I too would like to gear down the pump as well. I suspect i will have to just throw away what i have just build a new drive. IF if ever get around to it i will post a photo or two.

[DetroiTug]

"What would this reduction gear look like? How do you replace a cam with a gear?"

Search on Youtube or in the forum for Jack's Elliot bay triple. Its a small square tooth gear on the crank, meshed with a large one to reduce the speed. On the larger gear is a pin with a connecting rod or linkage that drives a pump. Also have a look at the compound in Wesley's boat. Wayward belle. it uses a real nice right angle worm gear setup.

[barts]

"What would this reduction gear look like? How do you replace a cam with a gear?"

Search on Youtube or in the forum for Jack's Elliot bay triple. Its a small square tooth gear on the crank, meshed with a large one to reduce the speed. On the larger gear is a pin with a connecting rod or linkage that drives a pump. Also have a look at the compound in Wesley's boat. Wayward belle. it uses a real nice right angle worm gear setup.

Right.. note that if there's room on the other side of the pump, placing the larger spur gear on the opposite side of the pump, replacing the existing eccentric w/ a smaller spur gear and using a connecting rod w/ a 'dogleg' actuate the pump across the top of the crankshaft is a useful trick.

- Bart