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Twin engined straight 8 Riley

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#1 r1leysp

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Posted 26 November 2013 - 15:37

Hi -In the process of building a Riley spesh. Mating 2 Riley nine engines to make a 2.2 litre bolide-thinking about the connection of the 2  .A pal recommends a duplex gear and chain (he saw a dragster with the front engine reversed and connected this way 2000 hp!) I will be keeping both engines in conventional setup and have thought about a viscouse coupling  ?. Another pal (stress engineer) reckons there could be trouble ahead under deceleration and at low revs. Someone else reckons rear engine -rear end of crank could be under too much grunt ?Me thinks thet by tuning engines in sync would overcome any negativity. Any input?


#2 fuzzi

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Posted 27 November 2013 - 14:35

You might like to look up the experiences of those who have gone before. Off hand I can think of:


Anderson Special (there's a 9min film on the Scottish Archives site) Mr Anderson built a couple of straight eights from a pair of fours. The first version used Austin Seven engines and the second motor used a couple of Humber Nines.


The Appenine Straight 8; built by an English enthusiast a few years using a pair of Alfa Romeo twin cams in a channel section chassis, clothed in a body based upon the Alfa Romeo 2900S. It was slated for production, but I don't think any more were built


The Harker Special used a pair of fours (first Austin Seven then MG) side by side on a common crankcase mounted first in an Austin chassis and later a Lombard.


Plus you have the Maserati V4 (4,000cc) and V5 (5,000cc) with pairs of straight eights and the Alfa Tipo A with a pair of straight sixes, both on common crankcases (the chassis and drive arrangements was used for the immortal Tipo B).


The first three still exist, and there are examples of the V4 including a superb recreation, built in England.


All of these geared the engines together.


Best of luck :wave:

Edited by fuzzi, 27 November 2013 - 14:38.

#3 gruntguru

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Posted 27 November 2013 - 22:46

I assume these are inline fours. Regardless - if they are even firing there will be considerable inertia torque and the only way to cancel this at the coupling is to synchronise the two engines.


An alternative would be new, cross plane crankshafts with cams to suit, like the Yamaha R1 "Big Bang". Haven't done the sums but this would probably permit a phasing that cancelled inertia torque through the coupling while allowing even firing for all eight cylinders.

#4 r1leysp

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Posted 29 November 2013 - 09:32

Yes I see where your coming to-there have been 2 other Riley strt 8 engines made the truble is that they have had a one peice block cast and a single crankshaft -probably also cams -my idea is to keep everything original as poss. Dont want to get too complicated as I want to get it on the track as soon as I can-also don't want to chop the chassis or do anything too radical-but do enjoy the challenge of getting it running right and having a long bonnet also the sound of a straight 8 (have a listen to the Farrelac-although a different firing order to everything). Maybe setting the cranks 30 degrees to start with-the firing order may be tricky as the strt8s gone before mine probably have different crank throws and cant  do the same .Anyroad this is theory at mo as the running gear brakes etc are being fettled -but enjoying all the possibilities which is more than food for thought.The  torque tube and prop shaft will have to shortened -this has been done many times before on VSCC specials but may be a problem  on an unshortened chass? My idea (please interject if disagreeing) is the car shud look good as well as go good-like the pre war Mercedes-the footage of them at Donnington  under power -the long bonnet forging ahead is out of sight literally. Think it will be trial and error hopefully not putting a leg owda bed. cant find the Anderson spesh-will keep on keeping on . :stoned:

#5 Lee Nicolle

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Posted 29 November 2013 - 09:47

From what I have seen with twin engines devices. Don't. Supercharge it maybe or just develop ONE engine and keep the other as a spare
The only one I have ever seen that was remotely succesfull was a twin rotary engined Mazda 929 Sports Sedan. A LOT less balance problems with a rotary, though it had some early. Though later it was replaced with a nice simple and far lighter all iron Chev and went a good bit faster.

#6 r1leysp

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Posted 29 November 2013 - 11:52

To compete in the VSCC races, sprints etc we godda go with them rules which is to keep the car period  heretidge cetra. Makes it a snadge hard to hide a small block Chev in a Riley chass . Wouldn't mind racing a coke bottle Camaro tho :cat:.

#7 mariner

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Posted 30 November 2013 - 17:48

Your VSCC rules may stop this but I have often wondered whether modern electonics can synchronize twin engines through very fast procsseing oft the spark signal.

Modern ECU's can detect a mis fie by noting the timing delay of flywheel acceleration per firing stoke so it might be possible to compare the signals from two ECu's and modify teh spark signal to drive synchronisation

#8 Allan Lupton

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Posted 01 December 2013 - 15:23

In your first post you report a valid point against: if you couple two engines in tandem the rear crankshaft, and in particular the rearmost crank web, has to transmit twice the power it was designed for. That's bad enough but you'll probably tune the engine for more power. Also, as the Riley nine crank is only a two-bearing job, the dynamic results can get complicated - e.g. when cylinder 6 or 7 fires and loads its already twisted crankshaft.

As for the overall dynamics some real straight-8s had crankshafts that were in effect two fours in line offset by 90 deg. but more thoughtfully arranged engines had one straight four in the middle and the other split two and two around it.

#9 Greg Locock

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Posted 01 December 2013 - 21:45

One way around the crankshaft torsional and torque problem is to mount the engines flywheel to flywheel and thake the drive off there. The mercedes I8s did that. It would be nice to decouple the two engines somehat, either by using a jurid coupling or cush drive in the system somewhere, or a fluid coupling as suggested earlier.

#10 r1leysp

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Posted 02 December 2013 - 10:46

Lots of great imput thanks-methinks I will try cush coupling 1st-then work from there-basically as long as the car looks period and there are no alternatives- later deviants can be used-all food for thought-will takem on board as project developes. After Riley- will be looking for trials project -the idea is to is to get up slippery slopes as far as poss-will be putting grey matter to  test with that -gyroscope ?-but now getting on with hubs and brakes for Riley-will keep up to date in this column with I am sure progress. :)

#11 r1leysp

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Posted 18 January 2014 - 12:16

Lo- have decided to put one engine only in special-after weighing up pro,s and cons -have decided that the rear engine is not up to job and would not be viable to modify ie rear main bearing - now looking for straight 8 engine or even big 6 -but in meantime will continue with one engine only-poss supercharge ?-thanks for imput which was great help in development of strategy.Will continue on with continueing on. :cool: