Building a race bike

motoddrob said:
That's a light frame Piet. Is it the same basic configuration as a standard SFC frame? Put the Motodd frame on the scales yesterday after receiving it back from repairs, 15.7kg.
The engineer who did the repairs reckon I'd save another kg if I put less paint on it!!! Probably did go overboard with the paint when last repainted.
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You saw it in Sydney, Rob!

Yes, basically same dimensions and lay-out as the stocker, but it seems to me the entire bike sits a lot lower than standard.  If I find the time, I'll pull it out and stand it next to a '74 SFC that's in the shop at the moment.  The frame goes a long way to keeping the overall weight to 150kg.

piet
 
"Out of balance forces are either in line with the cylinder or at 90? to the cylinder and crank axis, depending on the balance factor. "
Unfortunately it is not so simple and is indeed a dark art. The balancing work can focus the resultant (minimised as far as possible) vibration to a rev range and in a specific plane. There was an old bloke in Melbourne who worked for VicRail and whose workbench was covered in bike crankshafts. He was one of these magicians like Piet`s Herr Staschel, and those lucky enough to get their crank balanced by him found it hard to believe the results. He had learnt his trade balancing steam train drivetrains (good pun) and did it all static on knife edges.
Were all SFC frames CroMo Piet?
 
Might be my imagination but I seem to remember some vintage race engine I was reading about with access externally to the crank via a case panel you could remove and experiments happening adding and removing weight to see what effect it had without a full engine strip. I was impressed seeing a mate access the sludge travel on this bevel Gt Ducati via an access bolt for easy cleanout, hope I wasn't imagining that was well.
 
I believe some of the old pommy bikes have sludge traps in the crank that are cleanable through a port in the crankcase. But I imagine such a trap would be a simple radial drilling with a threaded plug in the periphery of the crank flywheel. Such a trap wouldn't have a lot of volume and would probably need to be cleaned out regularly. 

Laverda sludge traps (on the triples at least - dunno about the 750s) are contained by pressed metal disks which go full circle and would have a massive volume in comparison to a radial drilling. My Jota had done about 100,000km when I split the cases to replace a gearbox bearing. I checked the sludge traps while I was in there and they were about half full.
 
I remember reading about a shipment of Triumphs to the US which shook very badly. Big D in Dallas I believe worked out what was needed and simply drilled the crank in place after removing the sump plate...The mind boggles as to how they'd have done it if material had to be added....

Balancing is a pretty subjective thing. The engine either feels right or it doesn't. 180 deg cranks in twins can be an absolute pig to get acceptable wheras 360 deg cranks in my experience are usually quite easy. The angled engines usually finish up with a compromise balance factor - neither the full amount you'd use on an upright engine, nor the reciprocal figure used if it was horizontal. I can believe 55-60% for an SF. If the same engine had vertical cylinders it would probably be around 70%
We run 25% balance factor in the horizontal Aermacchis.
 
Dellortoman said:
Out of balance forces are either in line with the cylinder or at 90? to the cylinder and crank axis, depending on the balance factor. Assuming for the moment that the cylinder is vertical, 0% balance factor and all forces are in the direction of the cylinder - up and down. 100% balance factor and the forces are horizontal - fore and aft. Tilting the cylinder obviously tilts the out of balance forces.

You can do a lot of head scratching trying to analyse all this stuff on the drawing board, but achieving a good result usually comes down to trial and error.
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Kinda been answered already, but see Phil's comments about  BSA(?) frame. Play with balance factor and you'll definitely notice vibration focus shift. Might not add up in physics, but in practice it certainly does. Agree it is indeed trial and error!
 
my own Clegbiverdason, basically an Egli with an SF1 engine, vibrates the hell out my feet, the footrest cut their way into the boots I wore at the time, and left round trenches under the insteps., things were not known for breaking off though.
CLEM
 
Tippie said:
Were all SFC frames CroMo Piet?
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:D :D Fat chance.  If they had all the ancilleries of the road bikes, they'd be just as heavy as those!

My frame is a one-off, presumably built by Roberto Gallinas mechanic, or by Verlicchi, or... ::)  Nobody has been able to shed much light on it.

What I do know though, is that it works very well indeed!  Oz was its first outing, nothing was really tested.  Fine tuning the supension and gearing will release a lot of potential.

Currently running-in/testing a rebuilt '74 SFC engine, getting better by each km.  I only did about 15km before cramps set in, a friend is piling on the miles before it goes back to the owner, who wants it thoroughly tested.  Guess there are worse things in life... :D

Cam, sludge traps on the 750s and 500s are basically the same as the triples, only different diametres.

piet

 
Verlicchi made 3 ChroMo SFC frames, which were identical to the standard version.

Augusto Brettoni owns one of them.

Marnix
 
sfcpiet said:
You saw it in Sydney, Rob!

Yes, basically same dimensions and lay-out as the stocker, but it seems to me the entire bike sits a lot lower than standard.  If I find the time, I'll pull it out and stand it next to a '74 SFC that's in the shop at the moment.  The frame goes a long way to keeping the overall weight to 150kg.

piet
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Yes I did Piet, but didn't realize the frame was a special.` Can't understand then why the factory didn't make all the SFC frames out of chroMo. Surely the weight factor for racing would have been an issue back then. Don't know what my 74SFC weights but must be at least 60kgs heavier than yours. Almost equivalent to racing with a light pillion!!
 
It wasn't that odd to make frames out of Cr Mo back then either, all Husky frames were Cr Mo back then. What was odd was BSA made a Ti MX frame, that wasn't to smart as nobody could repair it as field welds for Ti didnt happen, some light reading from me.
 
A disc brake SFC frame weighs around 18 kilos, so to reach 150 kilos you need to remove or lighten a lot lot more. Starter and dynamo weigh 10 kilos, but when you remove them, the chain, freewheel, starter relay, dynamo cover etc etc can go too.

Do realize Rob that the US version SFC was really built as a road bike, with all the stateside requirements such as blinkers, mirror, huge SF2 style wiring loom, jota bars, double ND clocks on steel bracket, ND switches, speedo drives and what have you. It all adds up.

Marnix



motoddrob said:
Yes I did Piet, but didn't realize the frame was a special.` Can't understand then why the factory didn't make all the SFC frames out of chroMo. Surely the weight factor for racing would have been an issue back then. Don't know what my 74SFC weights but must be at least 60kgs heavier than yours. Almost equivalent to racing with a light pillion!!
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MarnixSFC said:
A disc brake SFC frame weighs around 18 kilos, so to reach 150 kilos you need to remove or lighten a lot lot more.
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My SFCr915 - based on a stock SF1 frame - was in the mid 160's kg.  Chris C reckoned it was 161kg but my measurement (still far from scientific) was more like 164 I think.  I saved almost 2kg changing from the maggy to an ignitech, in spite of having to then carry a battery.  In reducing weight the first gains come quite easy, then every extra step involves an exponential amount of effort.  It would be an achievement to reach 150kg with an SF/SFC based frame (and have it reliable).
 
sfcpiet said:
:D :D Fat chance.  If they had all the ancilleries of the road bikes, they'd be just as heavy as those!

My frame is a one-off, presumably built by Roberto Gallinas mechanic, or by Verlicchi, or... ::)  Nobody has been able to shed much light on it.

What I do know though, is that it works very well indeed!  Oz was its first outing, nothing was really tested.  Fine tuning the supension and gearing will release a lot of potential.
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In the meantime, Giovanni Laverda has confirmed the frame was built by Massimo Tamburini in his garage, possibly before any "production" Bimotas appeared.  Could make it the only Laverda Bimota, possibly one of the first Bimotas of all!  I've since found a pair of Ceriani GP rear shocks to replace the out-of-place Wilbers currently fitted.  Crankcase repair is scheduled for this winter.

Julian,

I'll throw a set of cases on the scales tomorrow.

piet
 
julian said:
Anyone know what the std engine cases weigh on an SF?
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Hi Julian,
SF crankcases are ~15,5 kg +/-500gr
(without studs but with oil splatter plates though).

I hope Piet will not blame me.
I've just weighted them a few days ago.

Cheers,
St?phane
 
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