A brake idea

HEY GUYS Let me bounce a thought off of you. I was messing with the Schwinn/70cc Gru Bee and took it for a ride after putting the pushbutton lock clutch handle from DAK on. I love it. No more suprise locks when stopping at corners and a nice smooth release when ready. I hooked up a light and got to wondering if there was room between the sprocket and spokes for a caliper when the thought came to me. THE THOUGHT>>>>>How about replacing the plastic idler on the chain with a #41 sprocket with a drum brake mounted outboard of it. A strong bracket could be clamped to both top and bottom fork tubes. If there were any question of the chain climbing the idler, stick a bit more chain in and a 2nd idler to curl the chain around several teeth, similiar to the rear deraileur on a bike. I have some cute little drum brakes from E scooters that might do OK since the braking effort would be good with a small diameter idler, or there is always the go-kart calipers. If you have any interest or thoughts, let's hear them.

updated idea on chain tensioner brake

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Here's what came to me in Carl's Jr.
I think the answer is not to slide the tensioner sprocket, but rather rotate another around it similiar to a deraileur to make an "S"around the brake sprocket and idler with the lash adjustment held with a locking screw. I did that on a 30 ft. conveyor belt drive chain that used to whip violently and it worked beautifully and amazed my supplier who is in the drive hardware business. . Another thought is to poorboy the brake by mounting a vee pulley of ~4-5" on the outboard and apply stopping force by pulling a section of vee belt tight with the anchor on the downstream of rotation so as not to lock it up tight by wrapping action. It should take a very light pull to stop well. It would need to be replaced periodically, but it's cheap. Another alternative of course would be an old leather belt riveted/glued to a sheet metal strap acting on a flat pulley. (Can you say Iron Caster Wheel?) I had an ancient American Motoscoot that worked that way. Gimme YOUR thoughts.

more thoughts on the chain idler brake

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More thoughts on the chain idler brake. I am slowly coming up with the criteria necessary to make it work. A real surprise was finding the E scooter brake, which is an external and constricting on a ~3" dia. rotor wraps in a self-energizing direction. It takes VERY little pull to put a stopping on it. We used to shut down 25,000 rpm FAI free flight model airplane motors (0.15 C.I.)with monofilament wrapping itself when the coil was drawn tight with a spring.. The braking effort shut them down in about 1 revolution when the timer dumped the pressurized fuel.
The braking sprocket needs to be the last one on the chain to reduce unnecessary stress on the assembly. The other would simply make the chain into an "S" to put several links in contact with the brake sprocket. It would be the lash adjustment adjusted by rotating it around the other and locking with a bolt in a circular slot. I found several 1/2" id X 1-1/8" od sealed ball bearings to carry the brake shaft but I need a stationary 3/8" bolt to mount the brake actuator on so I may still be looking for bearings. (it bolts to the axle and the scooter wheel carries the brake drum) The vee belt idea is looking better all the time. It would be a good starting place anyhow to test the concept. A bell crank could be used at the moving end of the piece of belting to multiply the effort if used in a non-self energizing direction. C'mon guys--
Speak up. Gimme your thoughts. I think this thing has the potential of being an excellent safe brake.

Re: more thoughts on the chain idler brake

I'm starting to make some progress.Tonight I discovered a Sears riding lawnmower blade arbor in the garage. It is smaller than the several others I recovered from the Sears repair shop dumpster. Ya gotta love those guys. They get someone's mower in the shop and replace most everything and throw the used good stuff away. This one has a 4-1/4" "A" pulley and a 4-hole flange. I ground off the weld at the blade holder and drove the 5/8" shaft out. I took about 1" off on the lathe and re-seated the bearing. I have decided to use a 18-T coaster brake sprocket for the brake. By putting a few links in the chain it will have several teeth in contact sitting on top of the bottom run of chain with the idler sprocket on the bottom in front of it making the "S curve. The bottom 2 flange holes fall in line with the lower fork. I will weld 2 studs for it on a piece of 3/16 X 2" plate and mount to the lower frame tube with 3/4" "U"-bolts. The pulley will be 2/3 toward the tire from the axle and the whole assembly from sprocket to outer pulley surface ~2-1/2". A strut will be welded rearward at about 45 deg. to the top frame fork tube with another "U"-bolt securing it to prohibit twisting. Since the shaft has a securing bolt thread in it for the blade, I will find a steel something with a keyway slot in it and mount the sprocket to it and mill a Woodruff slot in the shaft. The bolt will retain it on the shaft in addition to a setscrew, and the length just right to not crowd the bearing with end loading. The upper flange holes will retain a plate to secure the idler sprocket mounting plate from rotating. I will mill enough of the flange base so there is room for the rotating plate sandwiched between the flange and it's mount to the lower frame tube. The braking belt I will play by ear after I get the rest of this mess configured.brno

Re: more thoughts on the chain idler brake

Good progress tonight. I cut a piece of 2 X 1/8" plate about 6" long and scalloped a place for the bearing housing to nest and welded a couple of 3/8" studs to hold the bottom 2 flange holes I drilled out. The upper ones are still threaded and it looks like the bearing 14T idler will slide forward and aft on a beam on the top bolts to handle the slack. I have 7 links and a master coming as well as the idler sprocket , which was only $12 with shipping. 2 3/4" "U" bolts secure the plate to the bottom fork tube about 4" aft of the wheel rim. Everything like peddles and kickstand are safely clear. I will add another bit of plate to stabilize the assembly from twisting with another "U" bolt on the top fork tube.
I think I will destroy a screw adjustable steel pulley with a keyed 5/8" hole to make a spindle for the 18 T. brake sprocket. I will cut the shaft for a Woodruff key and use a setscrew and the mower blade bolt hole to secure it with running clearance for the bearings so as to eliminate thrust loading them. I need a reliable anchor for the piece of vee belt I will wrap around the pulley for braking force. I am thinking in terms of screwing a screw eye into the ends of the belt with epoxy in the threads and wrapping a portion with wire in place of a crimp ring. I can use one of the "U" bolt legs to anchor the eye. Anybody have a better suggestion? I'm listening,,,,

Tonight I made a sprocket arbor out of a steel 5/8" ID pulley. I turned the hub to the bore diameter of the 18-T coaster brake sprocket all the way to the flank of the pulley. The rest of the pulley was removed on the lathe clear up to the v face. I used the 3 jaws of the lathe to index with a gravity protractor and scribe on a copper surface made with sulfuric acid and copper sulfate crystals 120 deg. marks for the grooves to slip the sprocket into and milled them with a 1/4" carbide end mill. A groove was turned next to the sprocket for the retainer ring from the coaster brake. Wouldn't you know it was right spang over the setscrew hole. I assembled the arbor and trial fitted it learning the offset cup on the sprocket faced the wrong way and had to pick the snap ring out with hardly any room to expose the setscrew for removal. I will place the setscrew elsewhere next.
It now fits really well, lining up with the chain. The 14-T idler sprocket will be about 2-1/4" dia. and will be on a slotted beam secured to the top holes in the flange. Chain slack will be adjusted by sliding the beam fore and aft. This will give the needed 'S" curve for keeping several teeth in the chain. On looking the thing over, I find it would be simple to mass produce using one plate plasma cut to shape for mounting and a tube welded through it with bearing lands turned on the ID. I think 1/4" allthread joiner nuts screwed on the rear "U" bolts will supply enough rigidity to anchor the brake belt and cable pull to. It seems a bell crank at the pulled end pivoting on the joiner nut would give a leverage advantage and turn the action the direction I want to route the cable from. Then it would run up the upper frame fork tube.
I know his sounds like a diary but I am trying to give some insight into the design parameters involved in such a project for those that are interested in freelancing for themselves. I am well aware there are craftsmen here that make me look like a rank amature, but I am also sure there are others that just need a little urging to commit to such a project.

Re: A brake idea--God news-Bad news

The anxiously awaited sprocket arrived today. I milled the slot on the stock HT idler bracket to 3/8" and found the sprocket was a nightmare to align so it wouldn't eat the chain. My immediate thought was a BIG roller with ball bearings but didn't have the bearings. Thought number 2 was to run the chain OVER the brake sprocket. This gives me good engagement with 3 or 4 teeth and simplifies the system and reduces cost to produce units for sale assuming it works and makes alignment simple. Also it reverses the rotation of the pulley and makes anchoring the braking belt easy so the trailing end is anchored. I am leery of self-energizing brakes since the temperature of the belt could make reaction of the brake unpredictable. I found this to be true when I was escorting two friends who were driving a Ferrari and vintage Chrysler in a centennial parade and after slipping the clutch for miles, I almost ran over the Scottish Highland Band. The next problem is I need a #415 cranked (offset) link. I don't suppose there are any available anyhow. Plan B is now to make a 1/4" shim to add to the rear motor mount since the motor has to come out for frame painting anyhow.
This should solve the problem. If a link is too tight, I can ease the axle a mite since the peddle chain really needs a bit more slack anyhow.
DRAT-I left an O out of GOOD NEWS--BAD NEWS in the title line and can't edit it as usual.