Building an Aligator

JPigg55 said:
Great job !!!
Curious, what did you use to spec the size of the paddles and wheels ???
I have the dream of building a sidewheeler steamboat one day. Nothing as grandiose as this project, but similar.
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Thanks, there surprisingly isn't much information on the net about designing paddle wheels, go figure. Had to dust off some of my engineering books from a few decades ago and try and calculate how much paddle our engine would push through the water. Did the design based on the power we had rather than how much it would take to move the boat. It may take quite a while to get the thing moving. Basically used the torque the engine SHOULD develop with a full head of steam, multiplied by the gear ratio then how big a paddle it could push through still water at start up.
Based on hull speed which should be about 6 mph for 16 feet at the waterline the paddles needed to turn 20 rpm with a slip coefficient I managed to find somewhere. That set the gear ratio for the engine running at 200 rpm.
Basically there were a lot of best guesses involved so for a fudge factor we used a chain drive off the engine to the bull gear in case we need to tweak the ratio.

Greg
 
If you have the time and info, I'd be curious to know the spec on your boiler and engine. I reread that the engine is 5"x5" bore & stroke.
From the pictures, the boiler looks to be a horizontal fire tube style. Do you know what the tube heating surface area is ???
You planning on adding a drive pulley or gear to run an alternator for electric power for lights and such ???
 
Shoot a couple pins, pare of tractor tires and rims and it will walk on land. What a nice build , boy wish I were closer , I'd offer any help I could give.
 
JPigg55 said:
If you have the time and info, I'd be curious to know the spec on your boiler and engine. I reread that the engine is 5"x5" bore & stroke.
From the pictures, the boiler looks to be a horizontal fire tube style. Do you know what the tube heating surface area is ???
You planning on adding a drive pulley or gear to run an alternator for electric power for lights and such ???
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Took me a while but found a photo of the plate. 45 square feet heating area, rated at 5 HP 125 psi working pressure. Yes horizontal fire tube. Hadn't planned on trying to run a generator, may give it a thought but not really anything we need electricity for. Think this will be a daytime operation.
 
Thanks, I'll run the numbers in a couple equations I have.
 
From some formulas I'd ran across on a Steam boating forum.
Roughly 8-10 square of heating surface are per HP. So that pretty well matches the nameplate data (4.5-5 HP).
Using the PLAN formula, I come up with ~6.2 engine HP required for spinning engine at 200 RPM to achieve your estimated 6 mph hull speed.
These are all fudge factor number, be interesting when you get her opened up on the water see what she does compared to the math.

PLAN
P = pressure (average or mean)

L = length of stroke in feet (stroke in inches/12

A = surface area of the piston in inches

N = number of revolutions per minute (rpm)

PLAN/33,000=HP
 
Finally getting it in the water for sea trials will be interesting. As you said there were a few fudge factors involved in the paddle design.

Greg
 
f350ca said:
Finally getting it in the water for sea trials will be interesting. As you said there were a few fudge factors involved in the paddle design.

Greg
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This is interesting and I took a few minutes to read through your progress. It's good to see you're close to launch. Do you haul it somewhere close to launch it or just wench it to the closest body of water? :) This gave me a few moments to reminisce about my teen years in Florida scraping barnacles off of fishing boats in a small shipyard. The owner began work on his third and largest (90') steel hull yacht. I didn't see the launch but was able to board a couple of years later while home on leave. These projects are always pushing the envelope to get something accomplished. From a surplus magazine or CraigsList of that era he purchased two huge (for this purpose) Caterpillar engines in New Orleans that filled the back of a 24'-26' rental truck. I'm not sure why he rented an enclosed box instead of an open stakebed. Maybe it was the only thing available. But I remember wondering how he got the two engines in the truck, along with, he probably drove around the scales. There was always a project going, from another piece of steel being trucked in to overhauling the engines. Back to your project..

I understand the mobile progress across the lake towing the logs. What was the portage process? Did it require muscle pulling the winch cable to the next tie-off or anchor? Then the next question pops up: What mechanical means are employed to keep the alligator from being pulled apart?
 
We're going to have it trucked on a low boy for launch. We'd winch it the traditional way but haven't found a suitable winch yet.
Moving them overland must have been quite a task. After clearing a right of way, they winched themselves along using block an tackle attached to stumps I suppose. Attachment points for the blocks were built into the hull for the purpose of pulling. The boilers were hinged with jack screws on the end to keep them level while going up and down hills. The hulls were heavy. The sides were stacks of 2 x 6 layed on the flat, spiked together then rods drilled through to further tie the sides together. The bottom was heavy white oak planking with 8x8 oak skids capped with steel plate. Ours was scaled back slightly, we used 2x4 for the sides, spiked and 5/8 threaded rod from a top oak plank down through the side and bottom to 4 inch angle iron. The bottom planking is 2x6 ship lapped white oak. The skids are 3 layers of 2x6 capped with 1/4 x 6 flat bar.

Greg
 
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