Stupid ideas that would overcomplicate a build.

[cloakedvillain]

NeedSpeed, derailleurs require a freewheel somewhere, either at the front sprockets like in a shift kit and Shimano's front freewheel system, or the rear like the vast majority of bicycles. You'll need to figure out where to mount that freewheel.

What I had in mind uses these and a laser-cut plate with the correct spacings to bolt to the freewheel and the correct spacings for BCD of the desired chainrings. Scratch the left-hand freewheel part though. I see that there is no access to the notches required to remove the left-hand sprocket when installed. Not good!

Rear Hub Double Threaded Tandem Bicycle eZIP Electric Bike 36 Hole 3/8'' Axle | eBay

For The Not synchronized tandem bicycle, such as eZIP electric bike. The Silver Thread side is left threaded. The Black Thread is right threaded. Not receive, Product with a problem. Using or install issue, etc.

www.ebay.com

Bike Bicycle Freewheel Left Handed Thread | eBay

Left thread, No tooth. Using or install issue, etc. Not receive, Product with a problem.

www.ebay.com

A freewheel on the front can work for four strokes using an adapter that mounts to a keyed shaft, and the bt80 because it has a sprag clutch on the driven gear of the internal reduction.

More than half my mind says to let this idea lie. Too many custom parts!

 

[Sidewinder Jerry]

NeedSpeed, derailleurs require a freewheel somewhere, either at the front sprockets like in a shift kit and Shimano's front freewheel system, or the rear like the vast majority of bicycles. You'll need to figure out where to mount that freewheel.

What I had in mind uses these and a laser-cut plate with the correct spacings to bolt to the freewheel and the correct spacings for BCD of the desired chainrings. Scratch the left-hand freewheel part though. I see that there is no access to the notches required to remove the left-hand sprocket when installed. Not good!

Rear Hub Double Threaded Tandem Bicycle eZIP Electric Bike 36 Hole 3/8'' Axle | eBay

For The Not synchronized tandem bicycle, such as eZIP electric bike. The Silver Thread side is left threaded. The Black Thread is right threaded. Not receive, Product with a problem. Using or install issue, etc.

www.ebay.com

Bike Bicycle Freewheel Left Handed Thread | eBay

Left thread, No tooth. Using or install issue, etc. Not receive, Product with a problem.

www.ebay.com

A freewheel on the front can work for four strokes using an adapter that mounts to a keyed shaft, and the bt80 because it has a sprag clutch on the driven gear of the internal reduction.

More than half my mind says to let this idea lie. Too many custom parts!

If I'm remembering correctly on the Staton kit the 28t sprocket was closest to the gearbox and the 14t was the furthest out. Then there was a 28t that sprocket the screwed onto the SI hub which is very similar to what you have in your picture. A special adapter was made to put the 6 speed freewheel onto the outside shaft on the gearbox.

 

[cloakedvillain]

An acs southpaw with bolts between the teeth and a laser cut adapter plate with holes to match may work but that's really sketchy.

Sticking with a front freewheel means a disc brake mount could take an adapter plate for the chainrings but that limits it to four strokes and the e start bt80.

Needspeed, you could get two speeds with your gemini hub but it wouldn't be possible to shift without stopping. If you get longer bolts and spacers a 44 and a 36 could be mounted at the same time. That and an arch tensioner with a wing nut on the idler sprocket/skate wheel would let you stop, change speeds by hand and tension the chain. Angles wont be perfect for either speed, and you may have to dremel he case to allow for clearance for the angles but you get two speeds and you don't need a freewheel meaning you can still bump start.

Grubee sells built up wheels with left side freewheels that have the notches on the correct side for removal and a stepped thread to mount a disc brake. No bump starting though! https://www.grubee.net/collections/...roducts/26-hd-axle-wheel-for-4-stroke-engines

 

[ImpulseRocket]

Total loss water cooling:
A water jacket around the cylinder, no seals or check valves or anything, just like a pot of water. Engine sinks heat into water, and it boils out. No real benefit to cooling, adds a new limit to range. Not just fuel and rider fatigue but now you need to top off water on stops

Also called passive liquid cooling. No benefit?

As long as there is a liquid in that system, preferably water, the cylinder will never reach a temp higher than the approximate boiling point of the liquid in question. For water, that means the cylinder would always be in the low to mid 200 degree temps as long as there is water in the system.

The same principle has been in use for almost 2 centuries, and if designed and executed properly, can actually be incredibly reliable and extremely effective. The Browning M1917, and all previous Maxim based designs with water jacketed barrels, use this principle to devastating effect. An air cooled gun can only fire for a limited time before the barrel may overheat. A Maxim gun, or the Browning, can lay down continuous fire so long as there is water in the barrel jacket. The barrel is also thinner in these applications to improve the thermal transfer to the water.

The only real downside in an engine application is that you would have a range limited to water volume, but it could be a passive open condenser system. Hot water flows up, reaches a condenser (radiator) but with no pressure cap, cools, and flows down the system. Thanks to physics the water will circulate itself. There is still some loss over time, but the range is greatly extended. The water will freely boil, and the system is open to vent the steam so no pressure is built up, but since there is some cooling there is a lot less loss to venting said steam.

I think a system like that would be perfect for a motorized bike. No water pump, no thermostat, and about as simple as it gets, and even if you ran low on water, water is everywhere and cheap or free. Yes, it adds some weight and a little complexity, but I do think it would be perfectly practical for use in a motorized bicycle when considering how most of these bikes are used - short trips around town or into town.

 

[cloakedvillain]

I am familiar with bubbler pumps like in a coffee maker but I always assumed such a system couldn't flow enough water to cool an engine. If I read your reply correctly no check valve would necessary. The steam will naturally rise, condense and repeat. And that's not necessary because carrying spare water is easy.

Jb welding a water jacket should provide a sufficient seal, and ideally a one piece cylinder should be used for this mod to eliminate the risk of water leaking into the cylinder if the head studs get loose.

 

[robe]

How about this?
Cut all the fins off except for the bottom one. Cut a piece of 3" PVC pipe, glue this to the bottom fin, fill around the cylinder studs to seal it up. Fill with water.
Lots of details to figure out but there you are. Simple.

You could also use the cylinder head to cap this set up and have bungs top and bottom of the PVC pipe to a vessel of some kind. No pump needed, just convection would do it.

Maybe someone has mentioned this before?

 

[cloakedvillain]

In my mind the fins help with heat transfer. But I am not an engineer! Simple enough to use existing simulation models but it would take a for a processor to run through it all.

 

[robe]

I'm not an engineer either but water cooled motors don't have fins inside the water jacket.
I think if you did what I suggested the water would boil in short order making the whole arrangement not that great.

Some kind of reservoir would be needed so the water wouldn't have to be topped up all the time.

 

[Flight Risk]

Water cooling got me thinking of this fine machine with a hit-n-miss engine. He just needs to tow a cart with hotdog buns and mustard.

 

[ImpulseRocket]

No fins would be better. Water transfers thermal energy 25 times more efficiently than air. Robe has the right idea with removing most of the fins.

The whole premise of what I described works on the simple concept of convection. The condenser itself would act as the reservoir, and would be the highest point in the system. It's open to atmosphere so it doesn't build any pressure and allows the water to boil. You would definitely want some free space in said radiator/condenser in order to allow that water to expand and boil off without spilling out and spraying boiling water all over you as the rider.

As the water heats in the cylinder it flows upwards and pulls cool water up from the bottom of the cylinder, and the cooled water in the condenser sinks and flows down to the bottom of the cylinder helping to push the hot water up. The condenser just acts as a regulator that can help retain more water by preventing it from fully boiling off.

There are a lot of what ifs at work, so I can't obviously can't answer every single variable that pops up, but the premise is sound and has been used for over a century. Obviously, sealed and pressurized cooling that is pumped through the system is superior. I don't think anybody argues that fact. Seeing how underpowered and small these little 2 stroke engines are, they don't need a ton of cooling.