Greg Brillus Racer

[Nulli Secundus]

Thanks Phil,

The Rudge has a rigid frame, but only in terms of suspension !! The front suspension is only friction damped as hydraulic suspension is currently illegal in the BHR Girder Fork class.

I will tentatively try hanging off the Rudge, but like you think it will not suit it.

Cheers

Dave

 

[Canning]

Greg has had the racer completely stripped down again in an effort to make it faster.

In short, we are chasing more power, better braking and much more grip for higher cornering speed, and getting ready for the National Historic Titles where we hope to be very competitive.

Big changes to the engine with the Horner Brothers from Irving Vincent helping with the crankshaft balance factor, and new much higher lift cams with the engine going twin spark with ignition timing coming back from 36 degrees to 30. We anticipate softer bottom end power, but more acceleration and therefore better opportunities for overtaking between 5 -6500rpm.

The brakes have also come in for extra special attention with a Kevlar based high temperature lining and air scoops being made right now. This is because the racing Ceriani experiences fade in very hard high speed braking. We are really hoping this will be corrected as it’s been a weakness.

Last is a substantial change in wheel / tyre combination with 18” rubber on WM3 racing rims in place of 19” on WM2. This doesn’t sound much until you see the massive increase in contact patch that should result in significantly improved cornering speed. To do this, Greg has needed to change the ride height and other mods to accommodate the increase in tyre width. Have included a pic of the old rear tyre next to the new one mounted in the rfm just to get a sense for the change.

Greg really has been working hard to pull this together in time for the national titles in early November and I can’t thank him enough. As always, the quality of his work is exquisite.

 

[greg brillus]

So those flywheels are from the RTV days back in the 90's which had inner and outer counterweights to compensate for the Carillo rods and heavier pistons that those early 600 top end kits had. At the time when the crank was assembled I sent all the parts to Laurie Binns in Victoria who put it all together, and I remember he was a bit nervous about removing any of the counterweight in case it changed the balance factor too much. After I set it up and did my own calculations it turned out to have a balance factor of 89% Apart from a vibration at low engine speed the vibes would disappear as the rev's came up. It just shows how forgiving the engine is that the factor was out so much..........Ken Horner has now re-balanced it back to about 50% and this should make the engine much smoother. The only real defect within the engine was all the main bearing had to be replaced on account of corrosion/pitting on the outer races, and the two cam spindles showing signs of wear. The use of methanol and castor based oils is a magnet for moisture..........My only guess is that after I had my accident back in 2015 perhaps it was too long before I was up to servicing the bike, I am not really sure. The venting of the cases after a race event seems the most obvious remedy, changing the oil and rotating the engine periodically would definitely help too. It will be great to see how it all performs, as Phil has mentioned there are several changes we have made, and they all seem to be in the right direction. It should be back up and running within a week or so.........Cheers...........Greg.

 

[Chris Launders]

Hi Greg, Balance is indeed a strange thing. When I first built my Brough replica I had a bad vibration at tickover but after that it was smooth as silk at speeds up to 90mph (never had it faster than that) so I sent the crank off to be balanced, they told me it was at 86% and how come it hadn't shook itself to pieces as they're normally balanced at 42%. I can only assume they were flywheels for cast iron pistons, now it's balanced at 42% it's not as smooth but at least the forks want to stay in place at tickover !!.
Chris.

 

[BigEd]

Hi Greg, Balance is indeed a strange thing. When I first built my Brough replica I had a bad vibration at tickover but after that it was smooth as silk at speeds up to 90mph (never had it faster than that) so I sent the crank off to be balanced, they told me it was at 86% and how come it hadn't shook itself to pieces as they're normally balanced at 42%. I can only assume they were flywheels for cast iron pistons, now it's balanced at 42% it's not as smooth but at least the forks want to stay in place at tickover !!.
Chris.

Interesting. depending on engine/chassis setup there is usually a "sweet spot" at a certain RPM and finding the right balance factor for the RPM range you use most would be the key. I tried a few different balance factors on my Rapide but staying in the high 30% to 50% range. I didn't notice too much difference. The engine was always was pretty smooth. and bits don't break or fall off due to vibration. Balance factor, like life, is sometimes a compromise.

 

[Bill Thomas]

Anybody know why there should be a "Sweet spot",I would have thought balance is balance.
I have a Twin which is smooth at 70 mph, At 85 your teeth fall out, 90 + smooth again, But you have to come back through that 85 spot, When you slow down, And you wish you never went that fast.
I had the main bearing bored many years ago, God knows what he did, There is now a bit of end float on the Crank, That's not right !, I fear if I take it apart, It won't get put back again.
It starts well, Don't smoke, Goes like a Rocket, Just hope it don't go Bang !.
Cheers Bill.

 

[greg brillus]

Bill, There are a lot of things that cause harmonics within the engine, more often than not it can be several factors contributing to it. From what i can figure, a light piston can cause vibration at low engine speed and disappear as the rev's come up. I have ridden bikes that use to run very smooth, but after the crank was realigned upon an inspection of the internals for other reasons, now the engine vibrates very badly at low speed. If you are finding some end float, it sounds like the bearings on the drive side are moving. Are both circlips either side of the outer ball bearing.........?.........The only other time the crank moves is if the shock absorber nut is not tight, or is being held up by something or other.

 

[Albervin]

My Rapide is as smooth as silk up tp to 72 mph with a 48T rear sprocket. It then becomes a bit rough. The previous owner said it smoothes out again at 80 all the way to 120. I have to say that beyond 80 it does smooth both out but I will believe him without proving it. After all, it is 70 years old this month and it doesn't have the brakes from 70 let alone 120!!! I will leave that to my BMW and Aprilia.

 

[Bill Thomas]

Hello Greg, It's not the Shocker, It's been like it too long.
It was never smooth when it was on 12 to 1 pistons, But I was younger and did not Worry as much as I do now.
I worry that the Main Bearing repair was not good, And not something I could fix easy.
Only way is to strip it out , But I don't want to loose ride time, Plus the cost !.
I guess at my age, 70 ish MPH will have to be good enough.
Never seen it explained why it should be OK at one revs and not another.
Good Luck with yours, Is it not what we all want !, More speed, Better handling, Better brakes !!, Good laugh.
Cheers Bill.

 

[greg brillus]

The twin spark ignition we are going to run is quite clever...........Basically the mag is a Joe Hunt (Fairbanks Morse) twin outlet wasted spark magneto......Pretty common on older race bikes, especially on Pre-unit Triumph's, Bsa's and so on. There is an accessory that is produced by "Morris magneto's" in the USA that is a HT lead that splits from one into two with a junction box similar to a standard one into two throttle on a Vincent twin. This junction box houses two very high rating diodes set up in reverse polarity to one another. Some may not know, but a magneto is an AC device, that is, that as the armature rotates, the polarity reverses every 180 degrees. Because the magneto has twin outlets that fires both at every crank revolution, this polarity leaving each HT lead is opposite and alternating. As the spark travels to the junction box, the polarity of the spark is sent down only one of the output leads due to the diode that allows the direction of voltage to flow though it. Because there are two of these used, there are twin sparks available at the alternating output leads. Obviously the magneto needs to be timed correctly and the pairs of leads need to be checked and "Paired" before an engine run to prevent cross firing or failure to start. I have tested it by hooking up the HT leads to the four plugs in both heads whilst they were sitting on the bench, and you can clearly see both plugs spark at the same time as you rotate the magneto shaft back and fourth. For me it is a better alternative to running electronic ignition, with twin outlet coils, battery, and so on. Far less complication and weight saving as well.