opinions sought re small 12cyl twin turbo
Discussion
andygtt said:
Im always doing things professionals think I am mad attempting in my garage... however even I think designing and building an engine from scratch is an epic task to do right.
Worth mentioning that some of the people I have seen replying on here actually do this kind of thing for a living... so take heed of their advice.
The areas I would be concerned about in the design would be hot spots and oiling... not simple to avoid I expect... also how are you going to design out the chance of the engine producing a harmonic at any rev that destroys itself?
Id be basing the design around something existing which is what most of the bespoke engines I have seen have done... ie take a bike engine and use the heads on a new block and crank.
Good luck and keep us informed of progress.
I accept, appreciate and welcome all advice AND criticism and will heed warnings. Epic task yes. But I wanted a challenge Worth mentioning that some of the people I have seen replying on here actually do this kind of thing for a living... so take heed of their advice.
The areas I would be concerned about in the design would be hot spots and oiling... not simple to avoid I expect... also how are you going to design out the chance of the engine producing a harmonic at any rev that destroys itself?
Id be basing the design around something existing which is what most of the bespoke engines I have seen have done... ie take a bike engine and use the heads on a new block and crank.
Good luck and keep us informed of progress.
Oiling and hotspots is a concern but I think I can design a way to reduced/limit the possibility. All this is theoretical at the moment as stated in my OP but I do hope to be able to build it for real. Subject to more experienced approval/appraisal.
The harmonics are going to be my biggest concern and probably the most likely culprit for failure. I'd have to get a custom harmonic damper of course but they're only good to a point. If the firing order is panned out to eliminate the chances I think I'd be in with a chance of it being reliable, to an extent anyway.
Maybe someone could give advice on my current firing order and let me know what they think.
With regard to other bespoke engines, I don't want anyone to take this the wrong way or think I'm trying to be clever, but the way I thought about it was that if your going to make a bespoke engine yourself do it from scratch. Using another engine or multiples of is sort of cheating in my mind. I'm not saying its wrong and shouldn't be done quite the contrary. I would emplore anyone to do it if they so wish. I just wanted to do it differently. This brings more problems and likelyhood of failure but at least if/when I do get it done and its working sweet and reliable I can stand back and say the good old words "I made that"
Probably stupid thinking to some people but a sense of accomplishment like that would rival no other IMO.
I wish you well with the project but have to say the costs of going entirely bespoke will skyrocket and you will fail by that alone.
If you go the route of welding two or more engines together you could at least arrive at a working engine which will be a huge achievement in itself.
Inexperience aside I think money will be the deciding factor here.
Steve
If you go the route of welding two or more engines together you could at least arrive at a working engine which will be a huge achievement in itself.
Inexperience aside I think money will be the deciding factor here.
Steve
I've been thinking this over after a couple of boring night shifts...
Firstly get a copy of Karl Ludvigsens' book on the V12 engine, it will give you a few ideas as to the problems and pit falls involved and as I posted the other day there is a good section on firing orders which should help.
A couple of questions for the Op...
How bespoke were you planning on going and does it have to be 2litres? If you want to save a lot of time, money, R&D etc you could buy over the counter pistons & rings from a CRF150 dirtbike, it would mean either a shorter stoke or a slightly bigger engine though.
http://www.xrsonly.com/je-pistons-honda-crf150r-pi...
With regards the cylinder heads have you given any thought to how you were going to make them? Casting is far too involved and expensive for a 2off, plus spares. It would be much easier to machine them from a solid billet and then weld the water jacket around the ports etc. Again a dirt bike head would give you some ideas as to port shape etc which could be laser scanned to provide the machine code for manufacture. Valves, guides and seats could possibly come from a dirtbike too.
Cam shaft drive and where abouts on the crank also gears, chain or belt? I think it was BMW who built a prototype race V12 that had one bank driven from the front of the crank and the other from the rear, this allowed them to 'cheat' and use the same head for each bank. I'd go with gears for two reasons, first you can build up the gears in their own carrier so you can test them with out risking the engine and secondly they will sound >insert cliche here< at high revs!
If you take the cam drive from the center of the crank then you could bolt the cams onto a central gear allowing a shorter cam which would be easier/cheaper to make.
Crankshaft, Is there any reason it has to be one piece? A V12 crank is a big expensive lump of metal but if you were to build it up using Hirth couplings it would save an awful lot of aggravation. It would also allow the use of ball races for the crank bearings so you wouldn't have the same oil pressure problems Aston Martin had with their V12
For the crankcases again I'd take the top half from a solid billet but with the horizontal split below the centerline of the crank to help with keeping things rigid. I'd keep the barrels seperate from the head and cases for ease of manufacture and costs though and again I'd try to design it to allow for a welded water jacket.
Firstly get a copy of Karl Ludvigsens' book on the V12 engine, it will give you a few ideas as to the problems and pit falls involved and as I posted the other day there is a good section on firing orders which should help.
A couple of questions for the Op...
How bespoke were you planning on going and does it have to be 2litres? If you want to save a lot of time, money, R&D etc you could buy over the counter pistons & rings from a CRF150 dirtbike, it would mean either a shorter stoke or a slightly bigger engine though.
http://www.xrsonly.com/je-pistons-honda-crf150r-pi...
With regards the cylinder heads have you given any thought to how you were going to make them? Casting is far too involved and expensive for a 2off, plus spares. It would be much easier to machine them from a solid billet and then weld the water jacket around the ports etc. Again a dirt bike head would give you some ideas as to port shape etc which could be laser scanned to provide the machine code for manufacture. Valves, guides and seats could possibly come from a dirtbike too.
Cam shaft drive and where abouts on the crank also gears, chain or belt? I think it was BMW who built a prototype race V12 that had one bank driven from the front of the crank and the other from the rear, this allowed them to 'cheat' and use the same head for each bank. I'd go with gears for two reasons, first you can build up the gears in their own carrier so you can test them with out risking the engine and secondly they will sound >insert cliche here< at high revs!
If you take the cam drive from the center of the crank then you could bolt the cams onto a central gear allowing a shorter cam which would be easier/cheaper to make.
Crankshaft, Is there any reason it has to be one piece? A V12 crank is a big expensive lump of metal but if you were to build it up using Hirth couplings it would save an awful lot of aggravation. It would also allow the use of ball races for the crank bearings so you wouldn't have the same oil pressure problems Aston Martin had with their V12
For the crankcases again I'd take the top half from a solid billet but with the horizontal split below the centerline of the crank to help with keeping things rigid. I'd keep the barrels seperate from the head and cases for ease of manufacture and costs though and again I'd try to design it to allow for a welded water jacket.
now then,
the block and crankcase is as follows:
note the offset for the bores, this means that I could use the same identical units each side, allowing for a cheaper production cost, 2 identical patterns = cheaper to machine.
The heads were going to be billet, only the crankcase and block were going to be casted (rough) then final machined. in answer to a previous question I was considering casting these parts myself. The application of casting in itself is not difficult but getting the right scale to allow for shrinkage when the ally cools is where it can get tricky.
Cost for the crank as a 1 piece billet with the appropriate treatments is approx 4k from Arrow Precision, but that was subject to them getting a drawing and whether I wanted 1 or more. Not that bad for a custom crank. It doesn't HAVE to be a 1 piece however. Hirth couplings would save alot of aggro yes, I'll consider this and investigate it further. Wasn't the aston martin V12 using a flat plane crank aswell? IIRC that on it's own was enough of a problem, without the oil troubles.the block and crankcase is as follows:
note the offset for the bores, this means that I could use the same identical units each side, allowing for a cheaper production cost, 2 identical patterns = cheaper to machine.
Tango13 said:
I've been thinking this over after a couple of boring night shifts...
Firstly get a copy of Karl Ludvigsens' book on the V12 engine, it will give you a few ideas as to the problems and pit falls involved and as I posted the other day there is a good section on firing orders which should help.
I will do this asap and have a good red through.Firstly get a copy of Karl Ludvigsens' book on the V12 engine, it will give you a few ideas as to the problems and pit falls involved and as I posted the other day there is a good section on firing orders which should help.
Tango13 said:
A couple of questions for the Op...
How bespoke were you planning on going and does it have to be 2litres? If you want to save a lot of time, money, R&D etc you could buy over the counter pistons & rings from a CRF150 dirtbike, it would mean either a shorter stoke or a slightly bigger engine though.
I was going FULL custom/bespoke pretty much EVERYTHING would be custom, pistons, nimonic exhaust valves with stellite seats, 214 inlet valves, custom rods, crank, pistons, cams, rockers - all to my specs/design. It doesn't HAVE to be 2 litre it was just what I settled on being the most viable stroke/bore/cost wise - in relative terms.How bespoke were you planning on going and does it have to be 2litres? If you want to save a lot of time, money, R&D etc you could buy over the counter pistons & rings from a CRF150 dirtbike, it would mean either a shorter stoke or a slightly bigger engine though.
Tango13 said:
With regards the cylinder heads have you given any thought to how you were going to make them? Casting is far too involved and expensive for a 2off, plus spares. It would be much easier to machine them from a solid billet and then weld the water jacket around the ports etc. Again a dirt bike head would give you some ideas as to port shape etc which could be laser scanned to provide the machine code for manufacture. Valves, guides and seats could possibly come from a dirtbike too.
as I put above, I was going to get the heads machined in 2 piece, machine everything around the ports for the water flow and then have the other section of the head that takes the cams, rockers and valve springs, etc bolted on top - as I understand it this is how some or maybe most of the NHRA monster engines are built.The heads were going to be billet, only the crankcase and block were going to be casted (rough) then final machined. in answer to a previous question I was considering casting these parts myself. The application of casting in itself is not difficult but getting the right scale to allow for shrinkage when the ally cools is where it can get tricky.
Tango13 said:
Cam shaft drive and where abouts on the crank also gears, chain or belt? I think it was BMW who built a prototype race V12 that had one bank driven from the front of the crank and the other from the rear, this allowed them to 'cheat' and use the same head for each bank. I'd go with gears for two reasons, first you can build up the gears in their own carrier so you can test them with out risking the engine and secondly they will sound >insert cliche here< at high revs!
If you take the cam drive from the center of the crank then you could bolt the cams onto a central gear allowing a shorter cam which would be easier/cheaper to make.
I was considering helical geared for the cams but the cost would be insane, I decided on a chain drive (duplex) and 1 going to each cam bank (2 x duplex chains) but run them from the crank via a helical drive to an idler with 2:1 ratio for the chains to run off. central chain is a good idea but it would increas machining and crankshaft costs significantly I think, plus the centre main is in the way lol If you take the cam drive from the center of the crank then you could bolt the cams onto a central gear allowing a shorter cam which would be easier/cheaper to make.
Tango13 said:
Crankshaft, Is there any reason it has to be one piece? A V12 crank is a big expensive lump of metal but if you were to build it up using Hirth couplings it would save an awful lot of aggravation. It would also allow the use of ball races for the crank bearings so you wouldn't have the same oil pressure problems Aston Martin had with their V12
For the crankcases again I'd take the top half from a solid billet but with the horizontal split below the centerline of the crank to help with keeping things rigid. I'd keep the barrels seperate from the head and cases for ease of manufacture and costs though and again I'd try to design it to allow for a welded water jacket.
For the crankcases again I'd take the top half from a solid billet but with the horizontal split below the centerline of the crank to help with keeping things rigid. I'd keep the barrels seperate from the head and cases for ease of manufacture and costs though and again I'd try to design it to allow for a welded water jacket.
The crankcase pictured above is not finished - obviously - there's no sump
but that was the general idea of it. The way you suggest, you mean have the split through the centre of the bores? so it's bolted through from top to bottom? I may have read it wrong though The images if nothing else will more than likely give people something to laugh at lol.
Anyway, further to my post of last night. I have decided to take a different approach to my first build. I'll start another thread to discuss it as I'd like to keep this unmolested for when I return to it. I'm not giving up on this, just re-evaluating my current position. I'll keep posting here regarding any questions, comments or advice and look forward to hearing all of them.
I have to say, i think it's a very good descision to start on something a bit simpler and "get your eye in" so to speak! I'd love to see a nice compact turbo'd motorcycle parts based V8 done well!
If you use "off the shelf" heads, it massively simplifies the process, and will give you a relatively robust starting point from which to develop your own structures and reciprocating system ;-)
If you use "off the shelf" heads, it massively simplifies the process, and will give you a relatively robust starting point from which to develop your own structures and reciprocating system ;-)
SuperchargedVR6 said:
Evoluzione said:
SuperchargedVR6 said:
Why a 2 litre V12 over a V6 or V8, or even a 4 pot?
I'm just thinking that's quite a lot of frictional and pumping losses for such a small capacity?
Just interested really
Presumably 'cos it'll rev to the moon! Read here and check out how long ago it was:I'm just thinking that's quite a lot of frictional and pumping losses for such a small capacity?
Just interested really
http://www.supercars.net/cars/26.html
I seem to remember even further back than that they had a 1.5 litre 12 cyl pushing out amazing power for its time.
Although it has to be said these days we have much more reliable engineering and lighter materials etc so don't have to go to such a degree of small cc with loads of cylinders, sounds like a fun project though!
167hp/litre in 1975, blimey!
http://world.honda.com/MotoGP/history/RC166/
jimbob82 said:
The idea is to use the engine in a circuit racing car similar to an atom/caterham - no road use, just track.
Rather than trying to build a motor then select a racing circuit, why don't you select a racing circuit then build a motor that will defeat the competition (that is how most successful race teams do it). Speaking of successful racing teams, many of them start with an existing engine design and modify it to fit their needs.jimbob82 said:
@dblack1: I suppose coolness is a factor yes, but who doesn't like the sound of 12 cylinders going over 9000rpm? 
and because I believe I can, if you believe you can do something I think you should do it to the best of your ability, if it doesn't work out you put it down to experience and re-evaluate
I thought you were building a race motor? Why does it matter what your race motor sounds like? I think it would be worth your time to find the specific use of the motor you are designing and design the motor around the purpose rather than the other way around. and because I believe I can, if you believe you can do something I think you should do it to the best of your ability, if it doesn't work out you put it down to experience and re-evaluate To me (im not an audiophile) everything sounds the same at 9k+ rpms, if your looking for something that revs high and is reliable, many companies make cool reliable motors that rev to the sky
I don't mean to attack your design or idea. I think original ideas and designs are cool (which you pretty much said you were going for), but I think you would be better off finding the specific purpose of the engine first, then setting your expectations for the engine, then designing the engine.
As for saying you can't do it, its a lie, you can do it... It's just a matter of how much cost and time you put into it. If it was so hard to make a running motor, few people would ever rebuild an old motor or build a new motor from parts because it would often fail on them, but we know that is not true. But I wouldn't expect your first to work as well as you originally thought (especially with such an extreme design). Many people have been told they can't only to succeed at the "impossible".
Maybe see if you can have a chat with this guy....
http://www.motorcyclistonline.com/features/v12_cus...
http://www.motorcyclistonline.com/features/v12_cus...
As somebody who works in the engine design business, I think the OP is probably biting off a lot more than he can chew.
As MaxTorque eluded to earlier, you really need to be able to do all the key calculations prior to putting pencil to paper, let alone machining anything. The problem is that every time you guess you either add a potential level of unreliability or making the part too heavy or power sapping (particularly bad if this is the lube system or cooling system).
A book such as Heywood's is a good start
http://www.amazon.com/Internal-Combustion-Engine-F...
Taylor's books are pretty good too.
Adding turbochargers brings in a whole extra set of complications - turbo sizing, control system & calibration.
I think if the OP bought the books, did the calculations and felt confident in his ability to understand the fundamentals, he would be more satisfied than if he were to go and build something that may or may not work optimally at best and destroy itself in seconds in the worst case - something that anybody who has worked with prototypes knows can happen to the most experienced people in the biggest name companies and consultancies, especially during the first build phases.
As MaxTorque eluded to earlier, you really need to be able to do all the key calculations prior to putting pencil to paper, let alone machining anything. The problem is that every time you guess you either add a potential level of unreliability or making the part too heavy or power sapping (particularly bad if this is the lube system or cooling system).
A book such as Heywood's is a good start
http://www.amazon.com/Internal-Combustion-Engine-F...
Taylor's books are pretty good too.
Adding turbochargers brings in a whole extra set of complications - turbo sizing, control system & calibration.
I think if the OP bought the books, did the calculations and felt confident in his ability to understand the fundamentals, he would be more satisfied than if he were to go and build something that may or may not work optimally at best and destroy itself in seconds in the worst case - something that anybody who has worked with prototypes knows can happen to the most experienced people in the biggest name companies and consultancies, especially during the first build phases.
jimbob82 said:
thank you for the info Sir. I have got a copy of Heywood's book, only half read so far but that sheet is DEEP. Very informative book. can you link the Taylor one's your referring to please?
TIA
Try this:TIA
http://www.amazon.com/Internal-Combustion-Engine-T...
Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff