Doug MacRae
VIP MEMBER
- Joined
- Jan 28, 2010
- Messages
- 216
Not everyone wants to reveal their secrets especially in racing and I am not retiring from racing yet, although I fell off a few times in 2009 and lost to Kenny for the first time ( I should have retired right there ), I have slowed a bit.
It is possible that there is a better set up Commando chassis that turns in as quick, can be laid on it's side through an 90mph sweeper without a weave and is dead straight at 130mph. Anything is possible.
There is no credit for me, Herb Becker was the brainchild who built the bike, the ideas and fabrication were all his- I was amazed at the difference between this and my original flexi-flyer Commando racebike that weaved and bounced its way all over the track when you started to push hard.
I have raced against Seeley framed bikes, I don't think they have much if anything at all over this bike and mine doesn't buzz your hands to sleep like a solid mounted Seeley.
I am not going to get into shocks or steering dampers, just the chassis set up of the bike.
The modifications;
Looking at the side profile of the bike, you can see that the tank is a custom, shortened version of a Production racer- this allows you to get further forward and get your weight over the front wheel- the seat has been lengthened to compensate. Getting weight over the front is a good thing..
The bike has adjustable front fork rake- stock, 1 degree and 2 degree steeper. I always use the 2 degree steeper. The rake is changed using 2 eccentric machined aluminum inserts that go top and bottom where your normal head bearings would go. Then a smaller bearing is put in there. The maximum you can change the rake with inserts is 2 degrees, after that you are out of room. In the picture, you can see the insert- fat at the back and skinny at the front- the bottom insert will be the opposite.
To make the steeper rake work correctly, you need to use reduced offset triple trees to obtain good 'trail' numbers. Modern sport bikes have very reduced offset triple trees. The bike will now turn in very quickly to the corner.
A good headsteady is a good thing, Herb designed his own which works well but a good aftermarket one should do you fine.
A little frame bracing at the front is a good idea, to stop flexing.
The most important modification, in my opinion;
Early Commando frames have a cross tube under the transmission cradle- Herb used that tube at first to attach his cradle stabilizer block to, but on this frame the tube was added.
To this tube a machined aluminum block was clamped that extends up inside the cradle; a square of teflon extends slightly out from the block on both sides and this is cut to be tight to the cradle.
Now the cradle can only move front to back and not side to side at all. The buzz at the bars feels like a stock Norton to me.
The bike has 5 position adjustable rear shock height- quite simply there are 5 sets of 4 plates that bolt the shock bottom to the swingarm with a 1/4" height difference between each set. I use the the second lowest.
The most tricky bit of the bike is the adjustable swingarm pivot height. The swingarm pivot point behind the transmission can be adjusted to 4 different heights. You will see on modern bikes that the swingarm pivot point is very high- this is beneficial for bike squatting under acceleration and makes for better geometry for putting the power down. There is a plate welded to the back of the tranny cradle and there is an 'H' shaped piece that bolts the pivot point to the plate- this can be turned upside down giving another height and there is another 'H' shaped clamp that gives you 2 more heights. Optimum height is a bit higher than stock.
That is all necessary so you can then go out and do this-
Heat race at Mosport last year, going OK;
[video]http://www.youtube.com/watch?v=_Mg0cqNQeMg[/video]
I think the best video for handling is to watch my on board from tight, twisty Roebling Road where I was still hard on the gas- you can see how the bike transitions quickly from vertical to full lean and is solid coming through the 80 mph sweeper onto the front straight-
[video]http://www.youtube.com/watch?v=EuYrHKk9STA[/video]
That's it. It also helps to twist the rubber thing on the right handlebar toward you.
Thanks to Herb Becker and Walridge Motors.
It is possible that there is a better set up Commando chassis that turns in as quick, can be laid on it's side through an 90mph sweeper without a weave and is dead straight at 130mph. Anything is possible.
There is no credit for me, Herb Becker was the brainchild who built the bike, the ideas and fabrication were all his- I was amazed at the difference between this and my original flexi-flyer Commando racebike that weaved and bounced its way all over the track when you started to push hard.
I have raced against Seeley framed bikes, I don't think they have much if anything at all over this bike and mine doesn't buzz your hands to sleep like a solid mounted Seeley.
I am not going to get into shocks or steering dampers, just the chassis set up of the bike.
The modifications;
Looking at the side profile of the bike, you can see that the tank is a custom, shortened version of a Production racer- this allows you to get further forward and get your weight over the front wheel- the seat has been lengthened to compensate. Getting weight over the front is a good thing..
The bike has adjustable front fork rake- stock, 1 degree and 2 degree steeper. I always use the 2 degree steeper. The rake is changed using 2 eccentric machined aluminum inserts that go top and bottom where your normal head bearings would go. Then a smaller bearing is put in there. The maximum you can change the rake with inserts is 2 degrees, after that you are out of room. In the picture, you can see the insert- fat at the back and skinny at the front- the bottom insert will be the opposite.
To make the steeper rake work correctly, you need to use reduced offset triple trees to obtain good 'trail' numbers. Modern sport bikes have very reduced offset triple trees. The bike will now turn in very quickly to the corner.
A good headsteady is a good thing, Herb designed his own which works well but a good aftermarket one should do you fine.
A little frame bracing at the front is a good idea, to stop flexing.
The most important modification, in my opinion;
Early Commando frames have a cross tube under the transmission cradle- Herb used that tube at first to attach his cradle stabilizer block to, but on this frame the tube was added.
To this tube a machined aluminum block was clamped that extends up inside the cradle; a square of teflon extends slightly out from the block on both sides and this is cut to be tight to the cradle.
Now the cradle can only move front to back and not side to side at all. The buzz at the bars feels like a stock Norton to me.
The bike has 5 position adjustable rear shock height- quite simply there are 5 sets of 4 plates that bolt the shock bottom to the swingarm with a 1/4" height difference between each set. I use the the second lowest.
The most tricky bit of the bike is the adjustable swingarm pivot height. The swingarm pivot point behind the transmission can be adjusted to 4 different heights. You will see on modern bikes that the swingarm pivot point is very high- this is beneficial for bike squatting under acceleration and makes for better geometry for putting the power down. There is a plate welded to the back of the tranny cradle and there is an 'H' shaped piece that bolts the pivot point to the plate- this can be turned upside down giving another height and there is another 'H' shaped clamp that gives you 2 more heights. Optimum height is a bit higher than stock.
That is all necessary so you can then go out and do this-
Heat race at Mosport last year, going OK;
[video]http://www.youtube.com/watch?v=_Mg0cqNQeMg[/video]
I think the best video for handling is to watch my on board from tight, twisty Roebling Road where I was still hard on the gas- you can see how the bike transitions quickly from vertical to full lean and is solid coming through the 80 mph sweeper onto the front straight-
[video]http://www.youtube.com/watch?v=EuYrHKk9STA[/video]
That's it. It also helps to twist the rubber thing on the right handlebar toward you.
Thanks to Herb Becker and Walridge Motors.
