Extra Isloastics

swooshdave · Feb 9, 2010

If the sphere is big enough, the sides appear flat if you are close enough. Look at the horizon if you don't believe me. :mrgreen:

Tintin · Feb 9, 2010

swooshdave said:
If the sphere is big enough, the sides appear flat if you are close enough. Look at the horizon if you don't believe me. :mrgreen:

Well, the sphere is not very big which is exactly the problem. The rods are a few inches long and that's it. If that is your horizon you're living in a pretty small world.... :mrgreen: Just kidding!

But you're right that compared to the amplitude of the vibes the sphere is not that small - however four rods are better than three Isos are better than whatever Isos mixed with rods, that's the way it is IMHO.

Tim

swooshdave · Feb 9, 2010

Tintin said:
swooshdave said:

If the sphere is big enough, the sides appear flat if you are close enough. Look at the horizon if you don't believe me. :mrgreen:

Click to expand...

Well, the sphere is not very big which is exactly the problem. The rods are a few inches long and that's it. If that is your horizon you're living in a pretty small world.... :mrgreen: Just kidding!

But you're right that compared to the amplitude of the vibes the sphere is not that small - however four rods are better than three Isos are better than whatever Isos mixed with rods, that's the way it is IMHO.

Tim

The rods don't move that much, so if I was better at math I could tell you what the deflection was. I've seen it noted before in previous discussions, at it was less that the side defection of the iso, IIRC. Am I right?

bpatton · Feb 9, 2010

Tim, I agree with you, but almost all serious consideration about the isolastics, links or otherwise, goes out the window when you look closely at the Commando frame. I've had a frame on a frame table. It's locked on its side anchored by the headstock. When you bolt down the rear iso mounts you can bend the fronts at least 1/8" up and down with your bare hands without really trying. The same goes for the rear. This aint a Featherbed. The front downtubes are good at supporting the weight of the engine but are nearly useless at trying to locate the iso laterally. Tubes have great strength in tension and compression but not much strength by themselves to resist bending. That goes double for long skinny ones with no bracing. It is a loose relationship between the various iso's an any dimension.
I like the idea of adding a link or iso under the swingarm because it helps lock the cradle vertically and helps take the twisting forces out of the picture. All it has to do is deal with bending. It also helps take some of the loads off of the other iso's. It's all about spreading the loading. I wouldn't loose too much sleep about the lateral displacement caused by the arc of the sphere defined by its radius given by the length of the rod which is determined by the amplitude of the motion in the x axis. Been there 15 years ago. After many thousands of miles I've come to the conclusion that it doesn't factor into it.

And, I cheated. This rated at 0.020" deflection at 250lbs

bill · Feb 9, 2010

here is what I have made and run on my bike .

the bottom one is the way I make it now with a counter sunk bolt supplied.

grandpaul · Feb 9, 2010

I'm going with a taylor top steady that i had on the shelf, plus one of Windy's front steadies, plus a bottom link as shown a bunch of posts up; that should do it.

Doug MacRae · Feb 14, 2010

I suppose I should comment on this-- if my Norton isn't the best handling Commando in existence, it's very, very close. I don't want to divulge everything my builder Herb Becker has solved through 15 years of race development on the Commando in making it handle but here was his solution to the high speed 'wallowing' issue caused by the inherent design of the isolastics- the 'rod end' thing looks interesting but his solution was much more mechanically simple. We do have a plate welded at the back of the cradle which strengthens it from twisting (although it was not put there for strength- we have our four height adjustable swingarm pivot point clamped to it- the handling works better when the swing arm pivot point is higher- but that that is another story) - and the 'wallowing' was cured by welding a cross member to the frame from one side to the other at the back of the transmission - to this an aluminum block was attached which extends upward into the centre of the tranny cradle from below- to this, two teflon headed bolts are threaded which screw out and push out wards on both sides, pushing out from the inside to each side of the cradle. All side to side movement is eliminated but the cradle is free to move front-to-back all it wishes. I don't think it transmits an excessive amount of vibes either compared to stock but it has been a long time since my bike was stock.... I can lay this bike on its side through 90 mph sweepers with no problem, it's rock solid- and it took me to wins at Mid-Ohio and Daytona so it must work.
I don't have a lot of videos but my on board at Roebling 2009 shows the bike's handling well -twisty and with a 90 mph sweeper coming on to the front straight- http://www.youtube.com/watch?v=EuYrHKk9STA
If you look at the profile picture of my bike below, you can just see the aluminum block poking up into the cradle below the gearshift. You can see from the scuffing on my belly pan which is mounted flush to the frame that I started to drag it in the corners a bit.

On my way to winning at Mid-Ohio '08-

Hortons Norton · Feb 14, 2010

Doug, I would like to know a little about the motor. That bike just blows by the other bikes and has a great sound also, Could we start a new thread about the motor in this bike? Wow!!!!!!!!!! I gotta know what it has. Thanks, Chuck. :mrgreen:

mcns · Feb 14, 2010

Doug thanks for input I met Herb Becker last year and was impressed by his knowledge of these machines. I am going to be close to Kitchener Ont. next year to ask if this is only something he does for race purposes only.

When I walked into his garage it blew my mind to have a man of his age so devouted is a inspiration.
This is a man that makes his own norton crankshafts, and the beauty of it is I dont think he owns a computer( I may be wrong)

cheers.

grandpaul · Feb 15, 2010

I was wondering along the lines of something to keep the cradle in line with the frame, that's what the rod links do...

What an awesome bike and rider!

lcrken · Feb 15, 2010

Doug MacRae said:
I suppose I should comment on this-- if my Norton isn't the best handling Commando in existence, it's very, very close. I don't want to divulge everything my builder Herb Becker has solved through 15 years of race development on the Commando in making it handle but here was his solution to the high speed 'wallowing' issue caused by the inherent design of the isolastics- the 'rod end' thing looks interesting but his solution was much more mechanically simple. We do have a plate welded at the back of the cradle which strengthens it from twisting (although it was not put there for strength- we have our four height adjustable swingarm pivot point clamped to it- the handling works better when the swing arm pivot point is higher- but that that is another story) - and the 'wallowing' was cured by welding a cross member to the frame from one side to the other at the back of the transmission - to this an aluminum block was attached which extends upward into the centre of the tranny cradle from below- to this, two teflon headed bolts are threaded which screw out and push out wards on both sides, pushing out from the inside to each side of the cradle. All side to side movement is eliminated but the cradle is free to move front-to-back all it wishes. I don't think it transmits an excessive amount of vibes either compared to stock but it has been a long time since my bike was stock.... I can lay this bike on its side through 90 mph sweepers with no problem, it's rock solid- and it took me to wins at Mid-Ohio and Daytona so it must work.
I don't have a lot of videos but my on board at Roebling 2009 shows the bike's handling well -twisty and with a 90 mph sweeper coming on to the front straight- http://www.youtube.com/watch?v=EuYrHKk9STA
If you look at the profile picture of my bike below, you can just see the aluminum block poking up into the cradle below the gearshift. You can see from the scuffing on my belly pan which is mounted flush to the frame that I started to drag it in the corners a bit.

Thanks for the details, Doug, and the pics. Lots of interesting stuff to see on the bike. I've seen a couple Commando racers way back when, where pieces of steel plate had been welded on the lower frame tubes that kept the cradle centered in the frame. They were a lot cruder than Herb's approach, just rubbing against the side of the cradle, and eventually wearing away metal. They also were less positive in locating it, since the lower frame tubes do flex a bit. Herb's location more to the rear is also more effective in limiting swing arm sideways. A very elegant, and simple solution.

When I was racing my PR, I never had any handling issues, just using the original PR isolastics, even in its final form with the 920 engine and period 18" slicks. That's probably because I never pushed it anywhere near as hard as you do on the track!

Ken

Doug MacRae · Feb 16, 2010

If anyone is bored, I do have a couple other videos- I am not sure if I posted them here-
Oct. 11 '09- Herb fires up the Norton in Sportsman 750 trim in Alabama at Barber using the crank triggered starter he made- http://www.youtube.com/watch?v=HhDCqhkx2xg ( Sorry, in the half lap of practice seen here I got the sound off sync somehow when editing it )
Firing it up at Daytona- '09 http://www.youtube.com/watch?v=s71KQdn3Yh4
My win at Daytona '09- check out this start- http://www.youtube.com/watch?v=funNlm0XIFE -Ignore the 'Seeley' title my friend Kenny posted the video and he was on a Seeley. He posted it because I was in the hospital with pieces broken off my T3 to T6 vertebrae after my massive 130 mph crash an hour after winning when I had a rod bolt shear and the motor violently seize in the Formula 750 race - ( I think posted elsewhere on this forum about this ) - this was a very strange failure by a part that rarely ever fails as the motor has proven to be a reliable balance of performance to reliability. Anyway here is the crash - you can even see the ambulance crew come to get me as I was 'asleep' on the banking- http://www.youtube.com/watch?v=IwmXS_Q1rnw
The (now all new but the head since last year's Daytona) motor is a stock bore and stroke - Maney cases and barrels, Herb lightened crank, Herb rods, Tim Speigelberg ported big valve head, some extra compression, 7S cam, twin 38mm Mikuni carbs and big bore pipes. Believe it or not it runs on a points ignition via an old school 60's vintage Joe Hunt magneto. You sacrifice 1 1/2 - 2 HP running points but I love running without a battery. The motor has put out some respectable HP numbers on the dyno.

RennieK · Feb 16, 2010

Great videos, thanks for posting! man that crash was something else. It's interesting to see how the 1st. responders tend to your poor Norton 1st. Is that the standard procedure as dictated by you racers and owners? It is a beautiful bike.

You'll have to pardon my sense of humor Doug, as I know what it's like to arrive at an accident scene before the paramedics (not fun). I'm glad you pulled out of it like you did! Thanks for sharing the pics and info about your bike too. Yourself and Ken and others who are racing Nortons have made this and other threads very exhilarating for us! Makes me wish I lived closer to a track where I could watch this action in real life!

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