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Hi I'm new to this forum, thought I'd finally start to write up a bit of by build that I've been working on. About a year or so ago I decided to try and build myself a 4 rotor engine, I settled on Badingham it on the rx8 13b msp engine as I couldn't find anyone anywhere that had done one in this format. I wanted to use only rx8 parts for this build apart from water and oil system parts. After coming up with a few ideas for the eccentric shaft I came up with a way that would be possible to build one from stock mazda parts but combining it with the traditional way of doing things (this isn't 2 e shafts coupled together in the middle) as it doesn't work at all. This is the first I've ever seen anyone do it this way even if it does seem like the simplest way to do things. Now I'm almost at the stage where I'm about to start machining the shafts I thought I'd write about it, hopefully in the next few weeks of the new year.
The engine will be assembled in the same way as any other rotary engine, the measurements will be the same but the concept will be different.
I've decided to use the side ports system for the engine but enlarge them as to make the engine breath a little better and hopefully a bit more power. Hopefully I'll be able to put some photos on here in the next few days of things that I've done and plan to do with the design and then anything that will be made.
So this is one of the drawings that will make up part of the eccentric shaft, like I said the design is a new style that I haven't seen before so isnt tested but everything says that it should work. This design allows me to be able to use the same design as the 787b engine design with an oil channel down the middle of the center of the shafts, as I can't drill a 700mm deep hole I decided to mill the oil channels on the outside of this shaft. This will be able to supply the oil to all of the bearings as the path into the channel is the same as the 787b engine but the oil volume will be minutely higher? The extent rich shafts that I am modifying from mazda will slide over this shaft to give a 90° firing order of 1-3-2-4. The rear counter weight and flywheel nut will be mounted in the same way as they are not but the key way will be rotated as applicable. The from start section will be the same as the 13b also but with a custom pulley so I can use it with a dry sump oil pump as the stock oil pump isn't upto the task to supply oil volume and oil pressure.
Removed measurements from this drawing
Those siamese side ports will be a major pia . They are the worst design feature of the Renesis engine.
I have played around with a few ideas to get more flow from them on my turbo setup but it always seems to create other problems .
How were you proposing to increase port runner size without making new irons ?
Edit: I see you will have a wide centre iron which will mean you can have a decent port runner there . So I assume you will use two stock centre irons plus make one wider iron for the middle of the engine . Or will you use two modified mazda irons for that middle section ?
Those siamese side ports will be a major pia . They are the worst design feature of the Renesis engine.
I have played around with a few ideas to get more flow from them on my turbo setup but it always seems to create other problems .
How were you proposing to increase port runner size without making new irons ?
Edit: I see you will have a wide centre iron which will mean you can have a decent port runner there . So I assume you will use two stock centre irons plus make one wider iron for the middle of the engine . Or will you use two modified mazda irons for that middle section ?
The port runners and openings are what I'm working on now, I'll looking to see if I can remove the sleeving get from the exhaust and make new sleeves for this to see if this will help but just playing with a few ideas at the minute. I didn't really want to do the PP or semi PP as thats what most seem to do. Even if this becomes a restriction in the system it's something that I can sort at a later date after making sure that the engine goes together and actually has compression. I may see if I can machine the intake and exhaust ports to open them up and put a sleeve in to make them a little bigger but like I said I'm still working on it.
I'm going to be building an eccentric shaft that had 3 main bearings not 4, this will have longer bearing in the center plate with 2 modified stationary gears to create the center bearing. I borrowed this design from another member on here who build a 4 rotor but my bearing will work in the same way as the standard bearing and not trap oil leading to failure. Doing this with 3 bearings is possible as the eccentric shaft will be alot stiffer that there will be minimal bending. Doing it this was requires alot less machine work and a simpler way of doing it.
Any other suggestions I'm open too so thanks for the help
What are the thin pieces in the shaft for?, looks a little fragile, diameter looks about 20mm or so? also curious how you are going to lock the lobes to that straight shaft, as a key alone isn't enough, that will wear. you need something conical that gets pressed together. I would also see if you can get the shaft gundrilled for the center oil hole, as those grooves are not optimal. the oil will need to work against centrifugal forces at high rpm. I dont think it would be too expensive, and it's just better. but fyi, if I had to redo my e-shaft, I would make it exactly like the 787b one. more work yes, but it's better. Curious to see what you will make of it!
The port runners and openings are what I'm working on now, I'll looking to see if I can remove the sleeving get from the exhaust and make new sleeves for this to see if this will help but just playing with a few ideas at the minute. I didn't really want to do the PP or semi PP as thats what most seem to do.
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For the siamese port sleeves , i would just use the stock sleeves and leave them roll pinned in place . The best mod I have found is to deepen the 'V' in the divider so that it goes almost to the point where you can see through from one side to the other , but not quite . Hope that makes sense .
What that does is improve flow slightly without allowing reversion ,whilst making the divider less prone to cracking .If the engine is only going to be N/A they will flow enough so long as you have a runner as big as the stock side plate runners in that middle iron.
Look very carefully at the siamese divider , cracks almost always appear after moderate mileage and will eventually lead to failure of the sleeve entirely. They are made from inconel and are prone to failure . Making your own from any material less heat resistant than inconel will not end well.
What are the thin pieces in the shaft for?, looks a little fragile, diameter looks about 20mm or so? also curious how you are going to lock the lobes to that straight shaft, as a key alone isn't enough, that will wear. you need something conical that gets pressed together. I would also see if you can get the shaft gundrilled for the center oil hole, as those grooves are not optimal. the oil will need to work against centrifugal forces at high rpm. I dont think it would be too expensive, and it's just better. but fyi, if I had to redo my e-shaft, I would make it exactly like the 787b one. more work yes, but it's better. Curious to see what you will make of it!
The channel and grooved sections are for oil inside the shaft (the center section has changed a little to make a little stronger but think It should be okay)the center diameter will be 21mm but as I'm not going for huge power will be strong enough to take the power. There will be a conical price that will slide down the end of the shaft and pressed down and retained with a circlip after that. That's the only way I could think to do it as I couldn't do the conical method with a nut like on yours. but as I couldn't put an external thread onto the shaft otherwise I couldn't get the loabs past.
For the siamese port sleeves , i would just use the stock sleeves and leave them roll pinned in place . The best mod I have found is to deepen the 'V' in the divider so that it goes almost to the point where you can see through from one side to the other , but not quite . Hope that makes sense .
What that does is improve flow slightly without allowing reversion ,whilst making the divider less prone to cracking .If the engine is only going to be N/A they will flow enough so long as you have a runner as big as the stock side plate runners in that middle iron.
Look very carefully at the siamese divider , cracks almost always appear after moderate mileage and will eventually lead to failure of the sleeve entirely. They are made from inconel and are prone to failure . Making your own from any material less heat resistant than inconel will not end well.
Brilliant thank for the tips, just wanted to do something a little different with this 4 rotor compares to most.
Well, what about doing it like this?, Note that it's a 5 piece e-shaft, so it actually uses 5 main bearings instead of 3. I think cutting the lobes of a stock e-shaft and trying to use those will be extremely difficult though. With that much material removal stuff is going to warp a little bit, and since everything is already on size, there is no material left to grind it so it's all good again.
Well, what about doing it like this?, Note that it's a 5 piece e-shaft, so it actually uses 5 main bearings instead of 3. I think cutting the lobes of a stock e-shaft and trying to use those will be extremely difficult though. With that much material removal stuff is going to warp a little bit, and since everything is already on size, there is no material left to grind it so it's all good again.
I did see that photo somewhere and that's what the idea came from, when machining the stock e shaft my machinist at work said that doing the process slow enough there should be less stress put into the material so warping should be as minimal as possible if any at all. The wall thickness will be thick enough as to help prevent this and try an keep it in tolerance as there is a small amount of run out that is in my tolerances and the shafts that u have at the minute are perfect with none at all so should still be use able. When it comes to remove hardening the surface in going to be using plazma nitriding for the outside surfaces such as the long shaft but the internal bores will need to be gas nitride as I am award and have found a company that can do this without putting any distortion into the material, I'm not sure how this is possible but they have a way of doing the process without any so will be using them as they have a good reputation for this. With everything that I've designed so far I'm pretty sure that all of the specs check out and should work.
Here is the final drawing for the shaft, as I said it's been changed from the original design to aid strenght etc. This was the simplest way to do it that I could think of. If I were found be trying to get 600bhp then I think the shaft maybe a little weak for that but I'm not interested in that power to be honest. I think with the oil pump that I'm hoping to use then I think that the oil will have no problem getting into the shaft to supply oil to the bearings in this way, I can't be absolutely sure of this as it's never been done but from what I've work out then it will work.
This is the modified e shaft the other will be the same apart from the conical peice in one end. This is the new design for the center shaft section with new oil channels and grooves.
I've started to collect all of the parts that I need for the build, I have all of the center plates, front and rear plates, e shafts, stationary gears and others but in need of 4 rotor housings for the build.
Before cleaning After cleaning with light wire well only on the faces. Fromt, center and rear plates.Just need to modify the center plates to remove the oil filler necks and block them off, the center one will have a breather pipe and also an oil fitting to supply oil to the new center bearing that I'm making as this is a 3 bearing engine.
Just wondering about the coolant system, I'm thinking of using the stock water pump would this be possible to keep the engine cool? Just thinking of the 2 rear rotors getting too hot or would it be a good idea to tap 2 or 4 fittings from the water pump housing into the 2 rear rotor housings water jackets? Would this cool the housings sufficiently or just a waste of time?
being as your using 6 port MSP front and rears, wouldn't you need (in theory) another 6 port plate in the middle? Or else wouldn't you have uneven air/fuel flow to rotor 2 and 3? Unless you went with 4 port front and rears?
I could be very wrong, but it doesn't seem like an even running engine with this plate setup
being as your using 6 port MSP front and rears, wouldn't you need (in theory) another 6 port plate in the middle? Or else wouldn't you have uneven air/fuel flow to rotor 2 and 3? Unless you went with 4 port front and rears?
I could be very wrong, but it doesn't seem like an even running engine with this plate setup
I agree . I thought he was making a special middle iron to take care of this but it appears not...
being as your using 6 port MSP front and rears, wouldn't you need (in theory) another 6 port plate in the middle? Or else wouldn't you have uneven air/fuel flow to rotor 2 and 3? Unless you went with 4 port front and rears?
I could be very wrong, but it doesn't seem like an even running engine with this plate setup
What I'll be doing about this is blocking off one of the intake ports on the front and rear ports to allow for this so the intake ports and runners are all the same.
However I have looked to see if I could port the center plates to alow me to use both ports on the front and rear, but will probably go with the blocking off 1 of the ports.
I agree . I thought he was making a special middle iron to take care of this but it appears not...
Not what I'm doing is modifying a center plate to accommodate a center stationary gear not make a whole new plate, it's anan idea that I borrowed from another build thread on here, think his name was John.
curiosity also, why MSP plates? Guessing more available where your at?
The main reason that I'm using the msp plates and parts it to try and minimise and potential problems that can occur with mixing and matching parts from different engines, this reduces the things that I could get wrong. As I can see there isn't a 4 rotor engine made from parts made from a single design of parts, there mixed and matched and I wanted to not do this and keep things as close to my ideas as I could.
I also want to make a 4 rotor with side ports only, I haven't seen this being done from what I can see but I maybe wrong.
Another reason is that again it cuts down any potential problems with machining the housings to make a PP engine and damaging the surface on the housings as I haven't got experience with this surface finish at all at work.
and the other reason it that I can get them fairly easily and in very good condition with is a plus.
I don't see this engine making very good power in that configuration unfortunately . There are major flow compromises in both the intake and exhaust.
What about putting two siamese irons together in the middle to get the exhaust port runner size up to something that will flow as well as stock ? You could machine a lot of the sandwich portion of it away to lose some weight .
I don't see this engine making very good power in that configuration unfortunately . There are major flow compromises in both the intake and exhaust.
What about putting two siamese irons together in the middle to get the exhaust port runner size up to something that will flow as well as stock ? You could machine a lot of the sandwich portion of it away to lose some weight .
I disagree with this as there's a reason that mazda went away from the ports in the housings from engines like the rx7 to a side port solution like the rx8, if you look at the design of the 13b in the rx7 and with twin turbo and a few differences I admit it made 276bhp, with a NA engine on the rx8 it made 228bhp if I'm correct so I don't see the this being the problem at all. So maybe the power will suffer a little but compared to a PP engine but as I haven't seen this done before I haven't got a clue what sort of power it will produce but that's not the idea behind making this engine for me.
with the adding another plate to the center of the engine, if that what you mean, it would make the engine even longer causing problems of the eccentric shaft being even longer and possibly flexing more, also I did have a look at this would help with the design and couldn't see any benefits to this idea. I think the best idea would be to open the ports on the center plates to help with evening out the air flow into the chambers.
I disagree with this as there's a reason that mazda went away from the ports in the housings from engines like the rx7 to a side port solution like the rx8, if you look at the design of the 13b in the rx7 and with twin turbo and a few differences I admit it made 276bhp, with a NA engine on the rx8 it made 228bhp if I'm correct so I don't see the this being the problem at all. So maybe the power will suffer a little but compared to a PP engine but as I haven't seen this done before I haven't got a clue what sort of power it will produce but that's not the idea behind making this engine for me.
with the adding another plate to the center of the engine, if that what you mean, it would make the engine even longer causing problems of the eccentric shaft being even longer and possibly flexing more, also I did have a look at this would help with the design and couldn't see any benefits to this idea. I think the best idea would be to open the ports on the center plates to help with evening out the air flow into the chambers.
Another thing with making this center plate is that all of the water galleries would need to be rectified and probably be easier to make my own center plate but thats not something that I'm not considering doing.
12-30-16, 03:45 PM
