hello guys. i need your help. our team is thinking making a new 2 cylinder engine. it's water-cooled. 12cc. independent valve.
but here are two problems.
1. we are not sure to make a 2 stroke or 4 stroke engine. which one is better? if it's a two-stroke, we will make it 28cc. if it is a 4 stroke, we will make it 12cc.
2. the gear timely belt is designed in the middle of the engine to make it more compact. but we are also worried if the belt can stand the high temperature or wear when the engine is starting up.
what do you think? any ideas are much more appreciated. thanks in advance. and welcome to send me an email email@example.com
i would never put the belt drive in the middle,
if there are any problems you have to dissmantle the whole thing,
also i woud expect tightening and temperature problems.
Why do not use a “uprjght shaft” valve control?
It is more expensive but would be something special.
1 . 4-stroke and 2-stroke model motors cannot be compared with each other, unless they are exhibits for beauty. If you need maximum power at fixed speeds – 2-stroke, if efficiency, good control and flat load characteristic, then 4-ton is better.
Considering that engines with different working volumes are planned twice, the question should be formulated as follows: these are two completely different motors and for different purposes – which one to design and build in the first place to satisfy the preferences of a larger number of consumers. I do not know the answer to this question, I am personally not interested in two-stroke engines :) they are primitive.
2. As for the timing belt or starter, I modernize the old ones and design my 4-ton engines and I have formed my own experience and opinion. metal chain drives have no advantage on small motors and only cause problems. Modern polymeric timing belts reinforced with aramid fiber or steel wire benefit from all aspects:
- efficiency. the essence of the chain transfer is the rotation of the axis of articulation of the links in the interdental space, which leads to friction, wear and heating. whereas the toothed belt works without friction (elastic deformation only)
- noise and vibration. make any explanations here.
- weight. a metal chain with the same transferable power will have a greater moment of inertia when the rpm changes and will limit the throttle response if this is not the case due to springs and valves.
- wear and tear. The toothed polymer belt does not lead to wear even when abrasives are injected. the metal chain must be kept clean.
- belts are available and cheap. what about the chain?
- I can continue listing :)
in my motors I rely ONLY on the BELT!
the chain is possible if a copy of a real plague is being built and this is an important detail of the purpose of the copy.
3. now about performance at high temperatures.
now belts are made from polyurethane and isoprene. Both of these materials work well at a temperature of -35 … + 85 degrees for an unlimited time under extra load. If the belt is not used for power transmission as in the timing or occasionally as in the starter, operation at 100-150 is possible. Do not forget that although the chain is metal, it needs lubrication – and it can become a bigger problem under the same conditions! When designing an engine, it is important to understand that if it is water-cooled, then the operating temperature will not exceed 100C (everywhere except for the exhaust system). If you get the temperature of the crankcase, crankshaft, cylinder block and head more than 100 – this is already an emergency! because the coolant will boil! You will get local overheating, jamming and destruction of anything but a belt!
I love the SYNCHROFLEX® GEN III AT3 and T2.5 belts and the MXL isoprene belts are very good and available. I have never had any problems with belts except that I can’t get rid of them :)
4. I would not make more than one carburetor per motor unless it is an injector. The smaller the carburetor, the worse and more unstable it works, this is a consequence of the laws of hydraulics and hydrodynamics. to this it must be added that the synchronization of the operating modes of two or more carburetors is a headache for the user. a single carburetor will also be cheaper and easier to manufacture.
all I said is my personal experience and my opinion. it is possible that in a particular situation these recommendations and conclusions will not be appropriate.
Forget timing belt use metal sprocket like in a Honda RC30 mortocycle
I say you should make both! Maybe you could manufacture half and half. I’m sure many people will want a 2 stroke, and many will want a 4 stroke. Personally, I’d prefer it to be 4 stroke. However I suggest you manufacture both.
I’d be interested in seeing this process play out. Thanks.
Make it 2 stroke. I think its time we start getting some actual usable performance from these engines. This can be the race version of the toyan L200 and NR200 we have already. I like the idea of putting the belt in the middle of the engine but it would impact the serviceability of the engine. Also if it can be a single carb that would be great!