braddubya

Now to anyone who would like to contribute positively to the thread and not just try to make themselves feel better about their own failures...



I have been thinking about a good strong and reliable way to join the engines and one thing I came up with was machining down and joining a front and rear plate so that both bearings could still be used and then with the remaining are of the eshaft a larger diameter coupling would be used to join the engines. With this setup a draw bolt may not be needed as the bearings should hold the system together and as long as it was setup correctly the coupling would not "want" to separate. This should be very strong, but the downside would be that it would make the engine much longer and heavier and a slightly larger rotating mass. May be worth it however for the peace of mind.



Another thought was to machine out or machine an entirely new intermediate housing between the two engine that could hold a larger diameter bearing. In the bearing would sit a similar coupling as mentioned before. This would be lighter and shorter but requires more machining.



What do you guys think?

braddubya

I think the larger diameter spline sleeve coupling is key. It will be very strong and will not require a draw bolt to hold together like a taper coupling just maybe some pins or a press fit to make keep it from moving around. although the straight coupling has some disadvantage in spreading the stress compared to a taper it will make up for that with its larger diameter and the fact that it will work with solid eshafts instead of drilled out hollow ones.

wolfgang

have you thought about timing yet? Are you planning on having it run like a big 2 rotor where two fire at once or are you thinking of 4 smaller bangs more often?

braddubya

Im not sure yet. I know the 4 separate firings would sound better and run a bit smoother but im not sure how the balance effected (anyone want to enlighten me?)



The double seems easier and I think I may be able to use a single ignition system with this as it will still have the same fireing sequence

tonybcrazy

I to have been thinking about building a 4 rotor engine. Some things I figured would be difficult things to overcome would be dynamically balancing the engine. Dynamic balancing is almost an art and it would be key to keeping an engine from failing due to fatigue.



Also as a current cnc machinist with a degree in Manufacturing engineering I can see you needing some not so common machine tools. Specifically an ID OD grinder. To join e-shafts you are going to need to be working in the tenths range as in .0001 inches. Tolerances like that are past the practical limits of a lathe and you are going to want some good surface finishes and close tolerance fits which limits you to grinding or electrical discharge machining.

wolfgang

I was thinking of running them as 2 or 4 separate engines, IE have a separate ecu for each bank. it's now affordable threw the use of a megasquirt. I think the 26G used 4 bangs. Also 4 smaller bangs is easier to control, and has less instant force than two big bangs, so there is more room for error.

wolfgang

I really was not worried about the dynamic balancing. it would run a lot better if it is dynamically balanced, however my 13b was not fully dynamically balanced, and it runs great. The plan I had was to dynamically balance the shaft on my lathe, and then make sure the rotors weigh basically the same on a triple beam balance, Then double the amount of the weights at the end, and make sure they weigh the same too. Then we take the rotors, and the counter weights and spin them too. This should be close enough.



for a ID / OD grinder I have previously taken my little air grinder, and bolted that to the toolpost. Do you think that's going to be good enough. All of my tools are mechanical, as in I don't have cnc stuff. That was good enough for making my 650cc motorcycle an 835cc motorcycle, and fixing up some cams for the same bike but idk if it would be good enough for a 4 rotor.



I'm a systems analysis not a machinist, it's just my hobby.

j9fd3s

paul and i keep talking about a 4 rotor, and how easy it is depends on what you've got to work with.



you need to cast side housings, which paul thinks is simple, you just need to design the cooling passages



the e shaft is next, id stick with the 1-2-3-4 firing order (or whatever it is), its going to be hard enough to get the thing working that you dont wanna mess with firing orders....

wolfgang

Making a side housing is not that bad. Basically it's just a flat piece of stock, with some holes drilled in it. The hard parts are the side intake ports, and making sure it is flat, like really flat.



I was gonna cheat and use the stock housings, and machine them for a bearing.



Does anyone know the firing order of the 26g?

mazdaspeed7

This is only somewhat relevant, but there is TONS of great information here:



http://www.rotaryeng.net/