A brief explanation of part of the background to my preference for 270 degree parallel twins and 90 degree V twins. I'm probably not the best at delivering this explanation, but you can't argue with Physics :)
You can like what you like, but I prefer the 360 degree crankshaft. It reminds me of the BSA and Triumph motorcycles of the 50's and 60's. The GREAT sound and the GREAT performance that I remember so well. The 360 degree crank has a more even firing order and the performance of the Bonneville can never be disputed. In today's world I'd prefer the Kawasaki W 800 with the 360 degree crank and the wonderful chrome fenders. Man oh man I'm back in the 60's when motorcycling was fun.
60's Brit stuff is where it's at certainly and you're right that the Bonneville's performance is never in question, but it would be pretty dull if everything was the same eh. Cheers for watching :-)
Hi Dave, that just earned you a subscription - they both make sense . . . I've always had strange thoughts too (!) as to why 180 crank Laverdas seemed to pull harder than the 120's. In their case, eg. 1-2-3-gap as opposed to 1-2-3-1-2-3, I feel the gap is important in so far as it allows everything from the gear teeth to the molecules in the rear tyre rubber, to 'climb back down again' & regain their composure ready for the next three. Yes, you accelerate in a series of strong 'lunges' & it chews seven bells out of the drive chains, but watch a big horse pulling hard & they use the same technique to accelerate rather than a linear 1-2-3-4, even though they do have a 'four pot' transmission system. This is probably the reason horses aren't available in chain drive, just too much shaking going on as the power is laid down! : )
Ah, your explanation made me think of a possible reason my 3-cylinder Yamaha 850 had so much engine braking while my little 650 Honda 4 cylinder has so much less...the Yamaha's 3-cylinder has a nearly constant sum of piston speeds, therefore needing only a very light flywheel, while the flat-plane 4-cylinder needs a relatively heavier flywheel.
Well thank you very much. You've quite simply explained so very well why 270's work so well in terms of vibration, lighter flywheels notwithstanding. I'm the happy owner of the new Royal Enfield 650 twin and you've explained it very well.
Thankyou for this clear explanation of the advantages of the 270 degree engines. I was under the misunderstanding that 360 degree engines would be better because the power strokes are even spaced and you don't get two firing strokes closer together as well as the compression strokes clumped together. For me, all else aside the heartbeat like sound of 270 degree engines and 90 degree V twins have a far more pleasing sound. Really enjoyed your presentation. Cheers mate. Thumbs up :>)
+Bikes & Drones Cheers, it's taken me a while to get around to this one. It should really be about an hour long to fit it all in, but you get the gist of it in the time available. Thanks for watching, I appreciate the support
Just a small point, the most efficient point of piston travel is when the Conrod is at right angle to the crank which may or may not be mid stroke depending on Conrod length relative to stroke. See Phil Irving and 76 degree crank offset.
Phil Irving is undoubtedly an automotive engineering god. This vid is just the tip of the iceberg in what is an enormously complex subject, it was an answer to a direct question relating to it, but to answer your point: The most efficient point of energy transfer from piston to crank is when they are at 90 degrees provided the gas expansion within the cylinder at this point hasn't "tailed off", for example in a very "under square" set up. 90 degrees is never quite at mid stroke unless the crank is offset which presents other issues to be considered. Thanks for watching
The 270 crank has undoubted advantages in power delivery and smoothness, but parallel twins are emotive engines and steeped in tradition. This is where the 270 loses out. It does sound like a V-twin, and so if I like that sound a V-twin is what I would buy. The traditional (British) parallel twin has a 360 crank with even firing intervals and plenty of vibration. That is real twin character, for me. A lovely smooth sound. I also like the lumpy 180 crank used for smaller Japanese 4-stroke twins from the 1960s onwards. That's another sound altogether! Two stroke twins are usually 180 crank but fire evenly at every TDC - a totally different but equally wonderful sound.
Than you, I wondered where it would be advantageous for this kind of setup.I guess the vibration wold be greatly reduced as well. In 1962 I modified a Dominator 99 for racing, as well as the usual stuff for tuning I put the crank in a lathe and cut a of the flywheel material off, using Phil Irving's tuning for speed I used 66% as a balance figure weighing the con rods and pistons putting the right amount of material on the throws and drilling 1 inch holes in the bobweights. I reassembled the motor, the acceleration was mind blowing so was the declaration, I had to brace my arms otherwise I would slide up the tank!
+DukeDyson Thanks a lot Dave, that was well explained and I never thought of it that way. I too was under the impression that the 'symmetry' of 360 degree engines made them 'better' than the off-beat 270 degree ones, eventhough I love the sound and charracter of those far more. Really helpful, I learned a lot. Also didn't know the flywheels were lighter on the 270 degree engines and that too is a benefit I didnt know about. Thanks again! Han
+Han Mulders Cheers Han, I got around to it eventually. It could have done with being longer and more in depth (and probably more boring) but who'd watch that?
This is an A65 with an altered crank. It's cut in half and bolted at 90degrees to a new flywheel, it spigots neatly into this which ensures it's perfectly true. It uses a ring of bolts and two large bolts that screw into the sludge trap plug and crank, which are tapped to 12mm. These replace a sludge trap. This one is dynamically balanced around 50% and is very smooth. The dynamic load is reduced by around 40%. Great explanation. I doubt BSA understood what a great engine they had. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-lTMsn8P-Eyo.html
This is very similar except for using a long stroke Commando crank. Again bolted at 90degrees. This one is rubber mounted because the big engine defied being smooth enough. At 7780rpm the power curve is still not falling down but I didn't want to risk what might be the rpm limit for old bits. If it sounded like this coming past it would do it pretty quickly. 2nd is geared for over 100mph with this 5speed. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-x2SFZ7TEOMU.html
That's a fantastic piece of work for sure. I've seen something similar done to a Yamaha XS650 with great results. As you say, I wonder if BSA ever understood the potential of what they had? Cheers for sharing
Perfectly put buddy, and i got through two brews and one and a half eccles cakes while watching.... perhaps we should have a different system to just ordinary "Like or Dislike".... perhaps we could rate videos in "Number of brews"..E.G. "I seen Dave's latest video on crank configuration and intertia.....its a real Three Brewer!...... (same as an ugly bird on a Friday night would be a "four pinter".....!!!! pip pip..!
People talk of this as if its a new idea. Phil Irving designer of the Vincent engine in the 40's advised Edward Turner designer of the Triumph Twin engine in the late fifties or early sixties to adopt this format for the Triumph Twin as demand for increasingly bigger cc's was had issues of vibration and reliability. Edward Turner stated the ideal 360 deg parallel twin to be 500cc. Adopting the 270 deg crank would have given the engine the characteristics of a V Twin therefore allowing increased cc's without engine stresses and violent vibration. I often wondered why Edward Turner didn't adopt the 270 deg format.
You're absolutely right, it's not a new idea even though Yamaha try very hard to convince people that they invented it this century, but then they have a history of such things! Indeed there is very little new in the world, it was realised very early on the benefits of a V twin and thus an arrangement that mimicked it. My understanding of the history of it is that Edward Turner decided that to increase capacity would require more cylinders, he stated, as you know, that a single should be no greater than 350cc, a twin no greater than 500cc and so on but even he had to answer to the board and backers etc and so money for development was not always forethcoming. This is possibly partly behind his moves between Ariel, BSA and Triumph. Phil Irving was an engineering god, cheer was watching :)
@@DukeDyson Hello everyone. I think you're serious enough on this topic. I would have an issue with the exhaust. I have an old Honda CB 250 engine from 1975. This will soon be a race motorcycle. I would like to make a race exhaust system. The engine has a classic crankshaft. 180 degrees, as in the old two-cylinder Japanese engines. My main question would be: If the crankshaft is 180 degrees relative to each other, what kind of exhaust system should be made? Will the 2-in-1 system increase performance? Or would a separate exhaust pipe for each cylinder be the best solution?
Well explained Dave, was like watching Open University on BBC2 :) Simple really when you think about it. Was also good to see the phone interruption gave you a chance for some tea and cake ;)
+yankee doodle You noticed the tea and cake.....I thought I'd got away with it lol. Just off to buy some brown corduroys and elbow pads to make the next one more OUesq.
270 degree All The Way!! I have the Triumph America and love the torque and Engine Braking. Hardly ever have to use the brakes. And the sound with the right exhaust sounds AWESOME!!!
Cheers Richard, the picture in the background is my kids' school photo from some while ago. It is however the same school I went to. Cheers for watching
I was surprised when Norton chose this configuration for their 961 as the Norton purists would not have liked a vtwin sound. I would have thought they should have also offered a 360 degree crank version as per Triumph does
There are a number of advantages to this configuration, but you're right, the purists looking for a latter day classic will want the sound of a 360. Be interesting to see what the "new (again)" Norton do :-)
In the middle of each point you make, you side step to mention other forces. The impact of each point is then muddied and the flow of learning is slowed. Great points and good info, just clouded with side stepping.
Hi Robert, thank you for taking the time to comment. The imparting of knowledge is certainly not my forte, this was intended to answer a question about my reasoning during another vid as best I could. I accept your critique, hoping that you still found the opinion clear
I tried to explain this to my resident teenager and got tied up in knots. It just confirmed to him that I don't know what I'm talking about. Btw..I reckon you took the opportunity of having tea and cake when the phone rang. I'm sure I saw some sponge cake crumbs when you came back !!!
Good explanation.My own personal preference is two stroke! That's the only twins I have ridden. Never got round to riding a four stroke twin, a lot different I am guessing.I do like the sound of the Scrambler and TRX though.See you at Brightona :)
Cheers Matt, I was in two mind about publishing this as it's only one aspect of the physics that's going on, but someone asked so here it is. Cheers for your continued support Matt and thanks for watching
This is a very interesting subject, I wish I could sit down with you and discuss it further over a pint or two. In mechanics, everything is a compromise. The 270º crank has advantages and disadvantages. On a full 4 stroke cycle, 720º, work is only produced in 180º. On the remaining 540º the motor has a sort of negative power, it relies on the momentum generated during the power stroke accumulated as kinetic energy on the flywheel. On a two cylinder motor an uneven firing order robs the motor of some power due to the inevitable deceleration of the whole system created by the longer "wait" for the next power stroke. Remember, the Triumph Scrambler has 54 hp, the Bonneville has 62hp. When traction is an issue, like on the scrambler, the pros of the 270º outweigh the cons. Here's a nice video: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-oEXUrO5wYcE.htmlm11s I won't elaborate any more, maybe I'll chat on line soon. Um abraço, Alex
Hahaha ... I would ask the same questions (about the pints and about the 540º of "negative power") and would use the same bikes (Scrambler and Bonnie) as example when I decide to roll the page down to see if anybody had already comment about thins! Thank you Alex! Vamos tomar umas! hahaha Abraço Luca
Thing is though, if power is made though 180° of the 720° cycle, then the power delivery comes in a pulsing fashion doesnt it, therefore this pulsing rather than linear spread, is going to force the rear tyre into the road/track a little more giving more grip, and also the torque output of the engine is higher?? Im not stating btw, im asking, as im not too clued up on it tbh although i do find it fascinating👍
OK ... this is an odd question, but what would be the effect of a 90 deg crank? The power pulses would be delivered at the same points of rotation when comparing piston speeds (one at the point of direction change (TDC or BDC) while the other at its fastest) but closer together in time during the 720 degrees of rotation in the cycle. Would it make it feel more like an out-of-balance thumper? I assume they fire at 270 deg and then agan 450 deg later for smoothness. Do you know of any odd engine being designed that way?
I'm not aware of any twins that have such an arrangement, but my scope of knowledge is fairly limited beyond motorcycle engines. It does feature in some in line multis though. I imagine such an arrangement would require an enormous flywheel or some sort of balancing to prevent excessive vibration. I'll do a bit of research
+Tony Jeffery Cheers Tony, the standard Bonnys, the T100 and SEs etc and the Thruxton variant are all a 360 crank configuration, just like the original T120s & T140s of yesteryear
Great explanation Dave!!!!. Better throttle response, more internal efficiency, and better sounding. I'm sold...... 270 it is!!! LMAO. BTW, what crank does the Triumph Speedmaster have? Cheers! Mike
+Michael Rench Hi Mike, the Speedmaster, America and Scrambler have the 270. The Bonneville(s) and Thruxton have the 360, although there is some tuning differences between the models too, with the Thruxton apparently claiming the highest horsepower (for what that is worth). A Harley engine, on the other hand, goes like this: A piston fires. The next piston fires at 315 degrees. There is a 405-degree gap. A piston fires. The next piston fires at 315 degrees. There is a 405-degree gap. So Harley have halved the difference between to 360 and the 270 (315) on every other stroke and doubled it (405) on alternating strokes. So this is either the best of both worlds, or offers the worst of both. The Harley engine has only one pin and both connect to it, so they cannot fire at even intervals. In conclusion ... potato (waffle).
DukeDyson Oh you don't want to pay any attention to my waffle, Dave. Your explanation was excellent, I remember thinking back when I watched the Q&A that this was one conversation I hope to have with you in person one day. I've never forgotten that, and I hope next year when I can get some longer distance stuff under my belt on the new bike (secret squirrel, still deciding),, that this is something that might actuallly happen!
+pgod1960 I look forward to an opportunity to discuss stuff like this, but prepare yourself for a long visit. Hope to catch up with you when the decent weather returns. Ride safe buddy
Hi Duke. I found the video interesting (honestly). I couldn't help tuning in when you spoke about large crank and engine braking. I remember watching Trevor Nation and Steve Spray riding the Norton f1 in my youth. (Rotary wankle) The f1 engine had awesome acceleration but struggled with cornering partly due to zero engine breaking. please explain. RSMF.
Once sat on a bonnie T140 with a 270 crank and reved it up weird felt like it was gunna vibrate but never really did a kind of a hollow vibration without the hard edges but my favourite was the last of the old triumphs the TR65 a 360 that was smooth do know what they did but it worked
I do have just One question PLEASE sir. If for example there is a engine 'rated' at 50 Kw and 50 Nm, is it the SAME 'rating' regardless if it is a 180, 270 or 360 degree crank??? yes/no It is a simple question. I believe the answer is yes. - Regardless of the crank the engine will be 50Kw and 50 Nm. PLEASE confirm sir. THANK YOU. Regaeds.
Hi Terry, to answer your question it is necessary to have an understanding of torque an power. Torque can be thought of as the work an engine can do and as such 50Nm is 50Nm but it may be delivered at different revs for a different engine. Power can be thought of the speed at which the work can be done so a given torque at different engine speeds produces a different power so different engines at peak torque may produce different power outputs at that engine speed and equally two different engines at peak power may be at different torque for their engine speed. If two engines both quote 50Kw and 50Nm then that's what they'll deliver but they wont necessarily do it in a similar manner. Perhaps I should attempt an explanation video. Merry Christmas Terry
@@DukeDyson THANK YOU Duke. VERY MUCH APPRECIATED. - Perhaps maybe you misunderstood my 'question/example'. It is NOT ''2 engines''. Just 1 motor/engine. (a twin cylinder for example) And just supposing for example that the engine/motor was rated at say, 50 KW of power and had 50 Nm of torque, if the crank was 180 or 270 or 360 degrees, is the output/rating of the motor/engine still the SAME, namely 50Kw and 50Nm in this example? yes/no (all I want is, yes/no) 180 degree crank - 50Kw/50Nm 270 degree crank -50Kw/50Nm 360 degree crank - 50Kw/50Nm yes or no? Correct or incorrect? The motor/engine is 50Kw/50Nm REGARDLESS.of the crank????????? yes/no ( yes or no ) Thank You. (I hope this clarifies my point/question)
@@tpv59 It's impossible to give a straight yes or no answer to your question Terry, the "rating" you refer to is what the engine will deliver which may be different: If engines identical in every other respect have different crank configurations they will probably have different power outputs as things like pumping losses, for example, are less on a 180 degree crank and they tend to rev higher. The best comparison there is is probably the TDM850 which switched from 360 to 270 in about 1996 I think which gave it an approx 8% increase in torque but even that is not a completely fair judgement as it had an increase in compression ratio also. If a vehicle says 50Kw / 50Nm then that's what it delivers
@@DukeDyson THANK YOU Duke, You have answered my question. I do APPRECIATE the Time and Effort in your reply to me. You have answered my question. THANK YOU again sir. Hav a gd 1.
Arrr so that's why I like V twins so much...very well explained, got it....well I think I did...not quite sure actually ...could you go over it again....lol
I was so disappointed with the sound of my 270 degree Triumph America, to me it sounded like a sewing machine rather than a real Bonneville. I soon enquired about having the engine changed to a 360, but the cost was too high.
@@martindekker8203 I did, I had to, riding a sewing machine was so not cool! The new pipes just make more lots noise and change the resonant frequency, but I could always tell the difference and got terribly saddened with my bike when I heard an old T100 (with a 360-degree firing angle). I have sold it now. Considering getting an old T100.
@@PhilBusby I love my America 865 270 degree with TOR pipe sounds awesome. Prefer 270 degree over any other. But thats my taste. Certainly does not sound like a sewing machine more like Thunder!!!
@@martindekker8203 Isn't that what makes life so wonderful? Different people with different tastes! Enjoy your Bonnie America, It was by far my best looking bike (solo saddle and chrome luggage rack on back bumper!!!) Beeeuutiful!!!
I like all gas powered engines. Nothing like the sound & smell of exhaust & burning tires & the wind in your face. I think you can have a smooth whir of a Sport bike engine or a lumpidity thump thump of a Harley V-twin. Choose one or buy booth :) that's my simple explaination/decision LOL
