Balance factor
- Thread starter KERMIT1200
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D
Davo
Guest
Great read thanks Paul.
Dave
Dave
XBCoupeJota
Full member
- Location
- Race Central - Sydney
Dellortoman said:Sounds like it's all guesswork and everyone has a different guess. May as well just stick the sucker in the engine and see if it works
Yeh Cam reckon if you don't have a go you won't know what everyone else doesn't know 
Julian,
Red built the crank in my engine, re-phasing it from a 120 to a 180, I just couldn't deal with the thought of racing a Gay bike. Red was more than happy to liberate the 120 and turn the little sucker into a brow beating 180 thunderstorm.
All that was done was to pull it apart fit Carillo rods and put it back together in 180 form. It wasn't until later when Piet pointed out that Web no.4 is actually heavier in the 120 with a different balance factor that we realised the crank was not to the factory 180 spec. Reality is I believe it is better and through chance we may have found something better suited to our racing needs. I was always led to believe, machines built by the factory were a compromise and certainly Laverda didn't build any production triples for all out racing, they were road touring machines designed to last in all conditions.
So I am all for trying something different, extending the envelope and as Keith says "fortune favours the brave"
sort of back to front Crispin
180's have according to Piet 38%/0%/38% (may have been 35/0/35, I'm confused)
middle 2 webs are -20% and +20%
the 120's appear to have 38%/38%/38% and the inner web 4 is lighter then the 180 web 4
so that is what the Spaceframe would have now being a re-phased 120 liberated crank
will find out this week anyway, I stripped a Series 2 crank I had spare and removed the rods
pressed back together and trued up, he is going to measure this one first and we will see what we get
measured a set of standard conrods and the old Mondial piston/rings, etc so can calculate the balance factor standard no problem
machined up a drive mechanism for the crank to suit his machine, save some money
all ready to go tomorrow morning
Paul, good article
if anyone finds anymore please feel free to post the links here
we are all trying to learn this white man magic shite
Red
180's have according to Piet 38%/0%/38% (may have been 35/0/35, I'm confused)
middle 2 webs are -20% and +20%
the 120's appear to have 38%/38%/38% and the inner web 4 is lighter then the 180 web 4
so that is what the Spaceframe would have now being a re-phased 120 liberated crank
will find out this week anyway, I stripped a Series 2 crank I had spare and removed the rods
pressed back together and trued up, he is going to measure this one first and we will see what we get
measured a set of standard conrods and the old Mondial piston/rings, etc so can calculate the balance factor standard no problem
machined up a drive mechanism for the crank to suit his machine, save some money
all ready to go tomorrow morning
Paul, good article
if anyone finds anymore please feel free to post the links here
we are all trying to learn this white man magic shite
Red
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XBCoupeJota said:
Crispin,
The different webs in the 180 crank help to counter the rocking couple caused by the uneven cylinder spacing, the 0% balancing counters the outer cylinders that actually work as a 360? twin.
The 120 engine produces a rocking couple across the entire engine due to the firing order. This is far greater than the couple in the 180. Also, the outer cylinders don't have the middle one countering them, completely different altogether.
My racer also has a re-phased 120 crank, I've done the same for 2 other engines and all run quite nicely. No smoother than other 180s, but not rougher either. The stronger 120 mains might be able to iron out some of the vibes, I have the impression the 120 crankcase is also a bit stronger than the 180 version.
The crank in my 3C is basically stock, with the exception of carefully selected/matched RGS rods to counter the greater weight of the forged Asso pistons. This crank is actually a bit smoother than the re-phased one in the racer, the parts of which are also in stock form, running the same pistons. The 3C has full charging/starting sundries attached, the racer only has the starter freewheel stuff on it. Greater weight can dampen vibes to a degree, as Julian has already noted.
XBCoupeJota said:
When your competitors eventually catch up and make life on the track difficult, just re-phase the sucker back to 120? and enjoy a free 5hp advantage!!
piet
with the surgery this crank in question has undergone I'll be happy just to have all three crank throws balanced the same %
and not worry too much about what the % is
depends on what we find when we spin it, it may be way out and all over the place
am going to balance all 3 to same figure though
and not worry too much about what the % is
depends on what we find when we spin it, it may be way out and all over the place
am going to balance all 3 to same figure though
XBCoupeJota
Full member
- Location
- Race Central - Sydney
sfcpiet said:When your competitors eventually catch up and make life on the track difficult, just re-phase the sucker back to 120? and enjoy a free 5hp advantage!!
piet
Happy with the extra torque Piet
and the riders are real glad they don't have to wear a tutu 8)Never seen a 180 out-torque a 120, Crispin!
Given they are in the same state of tune, the 120 will deliver more torque AND ponies, it's just that the torque and power is so linear that you don't really feel it. The 180 is more in the face, the 120 subtle and smooth, which can be a real asset in a long-distance event. Gijs v. Dijk doesn't use the 120 configuration because he likes it so much.....
Besides, the riders can wear bad-biker-black tutus! Add a couiple of skulls and everybody will run and hide.
piet
Given they are in the same state of tune, the 120 will deliver more torque AND ponies, it's just that the torque and power is so linear that you don't really feel it. The 180 is more in the face, the 120 subtle and smooth, which can be a real asset in a long-distance event. Gijs v. Dijk doesn't use the 120 configuration because he likes it so much.....
Besides, the riders can wear bad-biker-black tutus! Add a couiple of skulls and everybody will run and hide.
piet
XBCoupeJota
Full member
- Location
- Race Central - Sydney
sfcpiet said:When your competitors eventually catch up and make life on the track difficult, just re-phase the sucker back to 120? and enjoy a free 5hp advantage!!
piet
Hey Piet, i'ld like to think we where way ahead of our competitors but Period 5 Forgotten Era Unlimited is now the premier class in classic bike racing, so much so that WSBK are talking about running a 4 round Historic Superbike world championship in conjunction with WSBK races in 2012. Reality is there is a resurgence in this type of racing and many top engine and chasis builders are directing significant funds and effort towards this form of motorsport. This years winner at the Island Classic set yet another lap record 1:38.964 on a 175 rwhp Suzuki Katana, his lap was so fast he would qualify in the top 13 of the National Superbike grid ahead of 20+ modern day superbikes.
So an extra 5hp and a Tutu isn't going to cut it, tell me where we can get 50hp and I may turn
XBCoupeJota
Full member
- Location
- Race Central - Sydney
julian said:CH3-NO2 is your friend! Or not,
People trying to follow you will love the smell,
Julian
May well be but unfortunately it's banned
in our classification of racing as is straight methanol. Steve B can run Methanol in the SFC as he is in an earlier class, Period 4 where it is still legal.
B
bob
Guest
This has been a really interesting thread but I'm still a bit baffled by this 120 to 180 crank conversion. Crispin/Red what performance benefits do you get by rephasing the crank in this way?
XBCoupeJota
Full member
- Location
- Race Central - Sydney
Hey Bob,
reality is the decision to re-phase the 120 crank was not based on performance, it was based on availability of a donor for my Spaceframe (an RGS). It was easier to secure an RGS as a donor at a more reasonable price than a 180 and it also gave the added benefit of a much stronger gearbox and as Piet has identified perhaps stronger cases as well. I didn't want to run the high frequency vibes in the solid mounted Spaceframe, I knew all about the tingles from a rubber mounted 120 after riding around Europe on a 120 Jota (great bike by the way probably the most fun Jota I have had the pleasure to ride).
Another benefit of the RGS 120 configuration is the crankcase baffle which 180's don't have (too my knowledge), I believe this extra baffling takes much of the swimming pool drag away from the crank and takes it closer to a dry sump operation. Indeed speaking to a couple of engineers in the know who worked on Cosworth and Formula Brabham engines, dry sumps provided an immediate 20% increase in horsepower between similar engine configurations. I run the Spaceframe in races with oil only up to the lower dipstick mark, around 2.5 litres to reduce drag (it's all short sprint races so no worries re consumption during the race), I believe the difference on the way a 180 and 120 spin up has to do with this factor as well as the phasing.
My 180 Spaceframe rev's very freely indeed, a much different engine to any 180 I have ridden before. I used the same engine in 120 and 180 format and it's not empirical evidence but there is no comparison of the pull it has now in 180 guise.
Piet would claim this as bollocks and that in a similar speck the 120 will out run the 180, but the 180 phasing of the 120 crank in the RGS cases, gearbox and crankcase baffles is a very happy machine indeed. Hence our next race Engine that Red is building and balancing now is based once again on a re-phased RGS to 180 spec.
And as Red says it just sounds so god damn good like a Laverda should.
Cheers Crispin
reality is the decision to re-phase the 120 crank was not based on performance, it was based on availability of a donor for my Spaceframe (an RGS). It was easier to secure an RGS as a donor at a more reasonable price than a 180 and it also gave the added benefit of a much stronger gearbox and as Piet has identified perhaps stronger cases as well. I didn't want to run the high frequency vibes in the solid mounted Spaceframe, I knew all about the tingles from a rubber mounted 120 after riding around Europe on a 120 Jota (great bike by the way probably the most fun Jota I have had the pleasure to ride).
Another benefit of the RGS 120 configuration is the crankcase baffle which 180's don't have (too my knowledge), I believe this extra baffling takes much of the swimming pool drag away from the crank and takes it closer to a dry sump operation. Indeed speaking to a couple of engineers in the know who worked on Cosworth and Formula Brabham engines, dry sumps provided an immediate 20% increase in horsepower between similar engine configurations. I run the Spaceframe in races with oil only up to the lower dipstick mark, around 2.5 litres to reduce drag (it's all short sprint races so no worries re consumption during the race), I believe the difference on the way a 180 and 120 spin up has to do with this factor as well as the phasing.
My 180 Spaceframe rev's very freely indeed, a much different engine to any 180 I have ridden before. I used the same engine in 120 and 180 format and it's not empirical evidence but there is no comparison of the pull it has now in 180 guise.
Piet would claim this as bollocks and that in a similar speck the 120 will out run the 180, but the 180 phasing of the 120 crank in the RGS cases, gearbox and crankcase baffles is a very happy machine indeed. Hence our next race Engine that Red is building and balancing now is based once again on a re-phased RGS to 180 spec.
And as Red says it just sounds so god damn good like a Laverda should.
Cheers Crispin
B
bob
Guest
Hi Crispin,
Interesting stuff! I wasn't aware of the extra baffles in the 120 sump, have they got some form of windage tray fitted? If so there is quite a bit of discussion on this subject on various forums. On the 500s the baffles are solid and these can exacerbate the problem of drag because in some circumstances the oil in the sump can swill around and remain on top of the baffle . The answer is to fit some louvred baffles [this was a mod they did on the works bikes] In the pic you can see a standard baffle on the left and a modified one on the right. The louvres face backwards so the oil drains clear under acceleration and in theory only surges forward under heavy braking, at which point the drag on the crank isn't an issue.
Regarding the high frequency vibes on a 120 crank in a spaceframe , in my experience they don't create a problem. My old bike successfully completed the 4 hour at Spa with no problems and Piero's machine has completed a number of 4 hour events with no ill effect. There are also plenty of rigidly mounted 120 triples in Rob North Tridents and such like on the racing scene which don't suffer from frame cracking or component failures. To stay competitive against Jap multis you need every bit of power and drivability you can muster and if I was to build another spaceframe it would definitely have a 120 crank . I reckon Red's new dyno will be revealing some interesting secrets in the forthcoming season!
Interesting stuff! I wasn't aware of the extra baffles in the 120 sump, have they got some form of windage tray fitted? If so there is quite a bit of discussion on this subject on various forums. On the 500s the baffles are solid and these can exacerbate the problem of drag because in some circumstances the oil in the sump can swill around and remain on top of the baffle . The answer is to fit some louvred baffles [this was a mod they did on the works bikes] In the pic you can see a standard baffle on the left and a modified one on the right. The louvres face backwards so the oil drains clear under acceleration and in theory only surges forward under heavy braking, at which point the drag on the crank isn't an issue.
Regarding the high frequency vibes on a 120 crank in a spaceframe , in my experience they don't create a problem. My old bike successfully completed the 4 hour at Spa with no problems and Piero's machine has completed a number of 4 hour events with no ill effect. There are also plenty of rigidly mounted 120 triples in Rob North Tridents and such like on the racing scene which don't suffer from frame cracking or component failures. To stay competitive against Jap multis you need every bit of power and drivability you can muster and if I was to build another spaceframe it would definitely have a 120 crank . I reckon Red's new dyno will be revealing some interesting secrets in the forthcoming season!
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G
Grant
Guest
Dunno, baffles me too...
Funny thing with "Perceived" power etc and crank phase is that often it is also part of the whole package, The power could be the same (although in general it has been proved that equal phasing is the best for "Ultimate" power) but the way it is given is VERY important! Not only in the "Big bang" type theory but also you must ALWAYS consider the "whole package" and that has to include the RIDER!
Even in a car,
We had one of the best historic drivers in the world driving for us "Rod Jolley" and if he does not feel 100% happy with the vehicle then he is seconds off of the pace! When all is feeling good and he has absolute confidence in the machine then he is regularly the pole setter in a car that in theory "should not" be. I think 180 vs 120 is a lot to do with the way it delivers the power and also that is part of the noise as even the best rider / driver in the world would be a liar if he said he "Never" cares about the sound and feel as long as he is faster! The human body just does not work like that in testing!
Something to think about!
Julian.
Even in a car,
We had one of the best historic drivers in the world driving for us "Rod Jolley" and if he does not feel 100% happy with the vehicle then he is seconds off of the pace! When all is feeling good and he has absolute confidence in the machine then he is regularly the pole setter in a car that in theory "should not" be. I think 180 vs 120 is a lot to do with the way it delivers the power and also that is part of the noise as even the best rider / driver in the world would be a liar if he said he "Never" cares about the sound and feel as long as he is faster! The human body just does not work like that in testing!
Something to think about!
Julian.