Gear Train
Other builders of Rudys Steam Tractor have mentioned that the speed of his tractor seemed too high. To slow it down, I picked gears that give a crankshaft to wheel ratio of 50.6:1 which means my tractor should move at a little less than half the speed of Rudys. One set of gears was added to the train to get the lower speed.
All gears are 48 pitch, 14.5 degree pressure angle, brass with an 1/8 face. The source was SDP-SI Drive Components,
www.sdp-si.com.
Even with all the choices of gears, it ended up that every gear with the exception of the countershaft pinion required some sort of modification.
Name Teeth Pitch Dia. Required Modification:
Crankshaft Pinion 32 0.667 Add hub & enlarge hole
Idler
(Compound) 80 1.667 Remove hub
(Compound) 40 0.813 Enlarge hole
Countershaft
(Compound) 108 2.250 Shorten hub, add setscrews
(Compound) 16 0.333 No mod required
Bull Gear 120 2.500 Reduce hole/hub dia. Setscrews
To add a hub to the crankshaft pinion, I made the hub, then turned an aluminum mandrel with a step to match the hub and pinion IDs.
Soft soldered the two together, removed the aluminum mandrel, then drilled and reamed to 1/4".
The idler compound gear was done using the same aluminum mandrel. I was concerned about getting solder in the smaller gears teeth, so I put the solder between the gears first.
It was a good plan, but poorly executed. I used too much solder and was pushing down on the top gear as the joint heated. When the solder melted the gear dropped into place, squirting solder out the edge. Luckily it only got into a few of the smaller gears teeth, but it made a mess of the large gear face. Cleanup involved picking the solder out of the teeth with dental tools and chucking the gear in the lathe and refacing it. Lesson learned: less solder, more patience.
The whole episode reminded me of a comment Rudy Kouhoupt makes in one of his videos about the best way of cleaning up a mess is to not make it in the first place.
The gear cleaned up fairly well and is fully functional, but you can still see some of the solder residue. Fortunately it will be hidden by the horn plate.
The larger gears came with a 5/16 bore that needed to be reduced to 1/4". This was done by turning a bushing, locktiting it into place and then trimming after the loctite cured..
Once modified, the gears meshed nicely and everything fit where its supposed to.
Dennis