Wow! What a delight. I certainly didn't anticipate this. I'm in your debt for providing that wonderfully instructive information. Just LOVE it!
Ok, I can see right away that this is an early Comet by the narrow rear tires. According to my notes, "Skinny rear tires indicate a Comet is mid 1960 or earlier production. Models 306X were sold with 4.80/4.00-8 rear tires on wheels secured by 4 lug bolts. Models 307X and later were sold with 16-6.50x8"rear tires on wheels secured by 3 lug bolts."
According to what I've read about decoding Snapper Comet model and serial numbers, my model 3081W serial number which starts with 82 was made in 1982 and left the factory fitted with an 8 horsepower engine. Since then someone swapped on an electric start 11 horse Briggs. So it probably makes more noise and uses more fuel even if the extra 3 horsepower aren't needed. Sadly, mine does not have the side brake setup shown in your photos. But at least now I know those parts exist. Perhaps I can find a set and retro-fit them. I'd like to experiment with how they could steer a passive-steered front caster supported Comet. I already own a new ball-bearing pivot-mount 8-inch pneumatic caster wheel, rated to carry either 300 or 350 pounds. It seems obvious to me that Comet's standard 2-wheel front steering will absolutely prevent duplicating ZTR-type mower turns where the machine simply pivots about a stationary rear wheel. But if we remove those front wheels, leaving the foot rests, and substitute one front-centered passively-steered large-diameter caster wheel, or two passively-steered large-diameter caster wheels, individually-operable rear brakes would enable our Comets to execute genuine ZTR turns.
While I want a set of those older brakes to fit onto my later-production old Comet, I would not want to endure those tiresome-appearing hand lever controls. Here are a couple of optional replacement systems.
1) A foot pedal control for each rear side brake, with or without "juice" brakes.
2) A steering wheel linkage which
a - progressively applies right rear brake when steered to the right
b - progressively applies left rear brake when steered to the left
c - applies no rear brake when steered straight
Either of these configurations would provide a much less tiresome way for drivers to apply rear brake steering than those electrical-tape-covered hand levers. If Snapper designers who were experimenting with this steering assist system never tried an easier to apply rear braking system, driver hand fatigue probably caused them to give up on this promising rear-steer system.
Also, their two front steering wheels absolutely limit turning sharpness. Yes, they can track pretty sharply, but they would have to skid on soil or concrete to execute turns as sharply as passively-steered front-caster ZTR geometry permits. Swapping one or two front passively-steered casters would remove that design limitation. Farm use experience has taught that large, robust single bushing caster pivots are much more durable and weather resistant than ball-bearing caster pivots. But for a trial run, my less weather-worthy ball-bearing pivot caster would do fine. If I were to make this steering-system conversion permanent, I'd try to find a farm-style grease-zerk-lubricated caster pivot.
Here's an image showing Comet's stock front steering geometry.
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Observe that each front wheel's steering pivot point is off toward the mower's center line compared to each wheel's center line. So tire rolling resistance drives both front tires toward "splayed outward" aiming directions. That outward splaying force is continually resisted by the steering links, but that control accuracy gradually degrades as linkage system wear creates slop. Those steering links both connect symmetrically but from opposite sides to the center steering arm, so those forces counteract each other. That balancing action means that even though those forces are being generated, you don't have to fight against them with arm pressure on the steering wheel or handle. Notice that as the 4 plastic steering linkage bushings wear out, Comet front wheel alignment becomes progressively worse, allowing the front splay force to steer the front wheels along conflicting paths. That causes front tire wear from continual tire scrubbing and slightly increases rolling resistance. If that steering system had been designed with natural-self-centering trail, they would naturally steer each wheel straight ahead. Instead, the designers choose to make the wheels fight each other all the time so any steering slop allows them to climb out of alignment. While your Comet is standing on its rear support, push the rear sides of its front wheels toward each other. If during that circumstance, your Snapper's steering linkage is sloppy enough to permit those wheel fronts to splay outward compared to each other, you should assume that it's allowing the same thing to happen while you're driving it. Now that I look at it, the front wheels in my photo appear to be splayed several degrees away from each other as they aim toward conflicting forward paths. If a commercial user put hundreds of hours on tires that far out of alignment, the resulting extra wear would soon become apparent. Previously, I thought almost all the high rolling resistance I observed while pushing my Comet about 100 feet on concrete was caused by the rear drive mechanism not completely disconnecting. Now I suspect its front end may be contributing significant friction. How well aligned are your Snapper's front wheels when moving forward? Those 4 steering linkage bushings have finite service lives. Need I point out that passively-steered casters don't cause these undesirable effects?
I know some trick "phantom hinge point" geometry which we used to make high security doors that hinged about an axis in space located before doors' front surfaces. Vandals can swing a hammer through the air where the phantom hinge axis exists because no physical mechanism exists there. I suppose we could apply that same approach to reconfigure Snapper front steering geometry. If I designed it, we could just disconnect the steering linkage and let the stock front wheels behave as passive-steering casters. But I don't think the results would be worth the effort unless it were to be applied to a production line where product volume might justify a more elegant design. Ideal phantom hinge axes would be close to vertical and located directly before each front wheel's center line when it is aiming the mower straight ahead. "Trail" is distance on the ground between a vertical line passing through the steering axis and another vertical line passing through the wheel's rotational axis. The higher the "trail" dimension, the stronger the self-centering steering effect. Too much trail would resist rear wheel steering force. Too little trail would fail to passively-self-steer front caster wheels. Those conflicting effects are easily balanced by trial experience information. I'd start with trail values like those used to make farm implement casters.
Ge-off, since your Comet already has those dual brakes installed, even though it would require hand control to operate them, how about trying a little experiment and sharing the results. Find, borrow or buy a big front caster wheel on ball bearings. Remove both front wheels from their axles. Then find some way to temporarily attach that big caster so it supports your Comet's front end at its center. You'd need to secure it little more firmly than with "bailing wire" to make a 5-minute trial run in your driveway and down the street and back. Just as a quick and dirty proof of concept trial, observations from this trial would be VERY interesting. I'll bet this easy change lets you spin your Comet about either rear tire at will. If you run this trial, let us know what you experience. 1960's Comet becomes an instant ZTR! :thThumbsU
And while you're playing with your Comet, check out how your brake levers are oriented in their pivoting joints. If you reversed them, wouldn't their handles be facing forward which would make driver effort in pulling them up a much more natural movement than pushing them backwards and down, reducing operator fatigue? Pulling up on a control handle to pull on a control rod seems like a natural action to me. Pushing backwards and down on a control handle to pull on a control rod seems like an unnatural action to me. Just an ergonomic design consideration. I think someone reinstalled them incorrectly before you owned it.
Does anyone have an old 1960's parts machine with those side brakes they'd consider pulling and shipping to me as cheaply as possible? I'd promise to photograph, describe and cause a driver to demonstrate how my ZTR-modified Comet configuration trials perform. This is your forum. If you want it to be entertaining and instructive, we need to support each other with what each of us brings to the table.
Also, which of my two rear-brake steering control proposals do you like better, 2-foot pedals or the dual-braking steering wheel?
John
