marinesteam wrote:
Math will bite you if you're not careful!
We might get our engines completed at about the same time, but I have a ten year head start
Ken
Math may bite, but w/o it all we can do is ritualistically repeat the successes of the past, or blindly vary
parameters and hope for the test.
And I hope to be happily steaming around in the completed boat 10 years from now...
Hey Bart, not a math question....
I noticed that somewhere back you mentioned a con rod big end of a 50mm x 90mm . I see that is .0314 smaller that the 2 inch crank. I think you could heat and shrink and install it on the crank journal, but I am wondering if the expansion of the bearing once the pin is installed will cause the bearing to be tight on the outer race. I've had this issue before but can't remember what to press fit difference was.
Ironman wrote:Hey Bart, not a math question....
I noticed that somewhere back you mentioned a con rod big end of a 50mm x 90mm . I see that is .0314 smaller that the 2 inch crank. I think you could heat and shrink and install it on the crank journal, but I am wondering if the expansion of the bearing once the pin is installed will cause the bearing to be tight on the outer race. I've had this issue before but can't remember what to press fit difference was.
Or did you machine the pin to 50mm?
The pin center is 50 mm, the ends are 1.948" to match the dimension to which I bored the cheeks. Aside - I need to make a proper tool to set the tool protrusion on a line boring bar; I find it difficult and error prone at present.
I fitted the pin as a thumb press fit to the bearing; this isn't as it's supposed to be, but I don't think a little extra internal clearance will be a problem. The amount of interference that's acceptable for such a bearing is measured in tenths IIRC. I've added spacers to either side of the bearing to center it precisely and will assemble w/ blue Loc-Tite.
Ironman wrote:Hey Bart, not a math question....
I noticed that somewhere back you mentioned a con rod big end of a 50mm x 90mm . I see that is .0314 smaller that the 2 inch crank. I think you could heat and shrink and install it on the crank journal, but I am wondering if the expansion of the bearing once the pin is installed will cause the bearing to be tight on the outer race. I've had this issue before but can't remember what to press fit difference was.
Or did you machine the pin to 50mm?
The pin center is 50 mm, the ends are 1.948" to match the dimension to which I bored the cheeks. Aside - I need to make a proper tool to set the tool protrusion on a line boring bar; I find it difficult and error prone at present.
I fitted the pin as a thumb press fit to the bearing; this isn't as it's supposed to be, but I don't think a little extra internal clearance will be a problem. The amount of interference that's acceptable for such a bearing is measured in tenths IIRC. I've added spacers to either side of the bearing to center it precisely and will assemble w/ blue Loc-Tite.
- Bart
I'm assuming you don't have a mill, which is why the line boring. In case I am wrong forgive me.
I would suggest instead of the boring bar to use a boring head from a mill. If you get one with a #3 Morse taper stub, you can hold it in the headstock with a drawbar. With the boring head you can adjust in very fine increments and do a great job.
Of course I have a Narex boring head, which is a thing of beauty and can increment in tenths, but I also have a Chicom head which will also get the job done for far less, if you never plan to get a mill.
Just a thought...
Ironman wrote:Hey Bart, not a math question....
I noticed that somewhere back you mentioned a con rod big end of a 50mm x 90mm . I see that is .0314 smaller that the 2 inch crank. I think you could heat and shrink and install it on the crank journal, but I am wondering if the expansion of the bearing once the pin is installed will cause the bearing to be tight on the outer race. I've had this issue before but can't remember what to press fit difference was.
Or did you machine the pin to 50mm?
The pin center is 50 mm, the ends are 1.948" to match the dimension to which I bored the cheeks. Aside - I need to make a proper tool to set the tool protrusion on a line boring bar; I find it difficult and error prone at present.
I fitted the pin as a thumb press fit to the bearing; this isn't as it's supposed to be, but I don't think a little extra internal clearance will be a problem. The amount of interference that's acceptable for such a bearing is measured in tenths IIRC. I've added spacers to either side of the bearing to center it precisely and will assemble w/ blue Loc-Tite.
- Bart
I'm assuming you don't have a mill, which is why the line boring. In case I am wrong forgive me.
I would suggest instead of the boring bar to use a boring head from a mill. If you get one with a #3 Morse taper stub, you can hold it in the headstock with a drawbar. With the boring head you can adjust in very fine increments and do a great job.
Of course I have a Narex boring head, which is a thing of beauty and can increment in tenths, but I also have a Chicom head which will also get the job done for far less, if you never plan to get a mill.
Just a thought...
I have a R8 Series 1 2hp Bridgeport and a 2" foreign boring head that takes 1/2" boring bars and fits in a 3/4" collet, but since I was boring 4" deep and up from 1" (largest drill I have), I was pretty dubious about using that setup. The line boring takes some setup, but definitely does a nice job in terms of parallelism and deflection. Looking at pictures of a Narex, I'd definitely consider using that... but those are spendy beasts indeed.
After a bunch of trips, home plumbing emergencies and other distractions, I got some shop time in last weekend and finished installing a DRO on my venerable Bridgeport - a project that stretched over several months. This seems to be working just fine, so I decided it was time to make sure the shafts were never going to spin in the crank cheeks. I drilled and tapped two 1/2 x 20 NF holes, 1 3/4" deep into the end of the crank shafts and put two set-screws in each, Loc-tited and fastened against each other. Unlikely to come loose . Now I need to do the other half of the crank.
In more design mulling I'm thinking about using a keyless bushing to fasten the flywheel to the shaft; these seem amply strong (3000+ ft-lbs) and help avoid stress concentrations plus the cutting of pesky tapers or keys. For the pump drives, etc. no keys are needed so long as tapered bushings are used.
- Bart
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-> That's quite a hefty piece of crankshaft! What will it weight when finished? I really like your design, especially the crankpin assembly that allows an easy & quick roller bearing replacement.
-> That's quite a hefty piece of crankshaft! What will it weight when finished? I really like your design, especially the crankpin assembly that allows an easy & quick roller bearing replacement.
The crankshaft includes some pretty heavy counterweights, which help act as flywheels since uniflow engines have considerable compression. The crankshaft will weigh right around 100 lbs when finished. There will be a flywheel at the aft end of the engine that has barring holes and which drives the prop shaft. That will add an additional 90 lbs if I go with the current idea of 3" wide hunk of 12" diameter round. Note that the width of the box keel precludes a larger flywheel, but dropping the crankshaft into the box keel means the prop shaft is dead level, and keeps it under the boiler and galley floor.
The prop of course is a much more significant flywheel since it's 28" in diameter, 28" pitch and weighs 60 lbs or so - same as a PT boat prop .
I think I need to make a small crane for moving the bits and pieces around and lifting them on and off the milling machine table.
I understand the mass for the compression cycle. Too much mass, fast reversal as is sometimes needed, may be difficult. I would only add as much mass as needed for reliable low speed engine operation.
I used to let the boiler pressure get down too low coming in to tie up and fast reversal was impossible and it made for some scary dockings The big 4-blade prop just drove the engine on low steam pressure. In New York another tug backed right out in front of us and I had to do an emergency reverse at full steam pressure, she shivered and barked out the exhaust, but we were able to stop and go back quickly.
- one test is worth a thousand expert opinions.
Re: Sea Lion Engine build
The big 4-blade prop just drove the engine on low steam pressure. In New York another tug backed right out in front of us and I had to do an emergency reverse at full steam pressure, she shivered and barked out the exhaust, but we were able to stop and go back quickly.