Extra Isloastics

Hi Guy's,
New member, long time rider, commando owner 13 yrs, Aussie

I like would to try something I have only heard about!

I wish to place an iso on the gearbox cradle underside of my 1974 850.

Any advice or pictures of a successful attempt would be appreciated.
I have a spare gearbox cradle, I thought I might butcher and weld to existing cradle and tabs on framework.

Reason; Better high speed handling on rough Aussie roads

Thanks Shane

unaproachable said:

Hi Guy's,
New member, long time rider, commando owner 13 yrs, Aussie

I like would to try something I have only heard about!
I wish to place an iso on the gearbox cradle underside of my 1974 850.

Any advice or pictures of a successful attempt would be appreciated.
I have a spare gearbox cradle, I thought I might butcher and weld to existing cradle and tabs on framework.

Reason; Better high speed handling on rough Aussie roads

Thanks Shane

Click to expand...

Hmm, I'd probably recommend adding rod ends to the set up before adding another iso.

engine-plate-t5527-30.html#p52581

unaproachable said:

Hi Guy's,
New member, long time rider, commando owner 13 yrs, Aussie

I like would to try something I have only heard about!
I wish to place an iso on the gearbox cradle underside of my 1974 850.

Any advice or pictures of a successful attempt would be appreciated.
I have a spare gearbox cradle, I thought I might butcher and weld to existing cradle and tabs on framework.

Reason; Better high speed handling on rough Aussie roads

Thanks Shane

Click to expand...

Hi Shane and Welcome.

If your goal is to improve handling then you might want to consider an aftermarket headstedy first. If you run a search on John Tayor, CNW, and Norvil headsteadies you can get a feel for what's out there. Kenny Dreer's 880 bikes had a third iso under the trans and eliminated the headsteady altogether. I hear that the reason was that he was using alloy cylinders and was having trouble with ring sealing due to the loads on the motor by the headsteady. Castiron cylinders don't seem to be affected by using aftermarket headstedies.
There are limits to using an under the trans iso or rod linkage for that matter. The frame just isn't up to it. The tubes are thin walled and there isn't any good way to spread the loads. Iso's really aren't the best way to control the drivetrain. Rod linkages may have some advantages. I think the best bet would be to try an aftermarket headsteady. If you're still not happy with the handling you can add something under the trans and get a four 'iso' setup. I think spreading the load is the way to go with a frame like a Commando's. It goes without saying that there are about a dozen things in the setup of a stock Commando that can be causing handling problems and Commandos have no creds in the Adventure Cycling world.

Yes, Kenny put one on the cradle.
This is also caused an interference with the side stand to properly return and tuck in.
Consequently, I ran without a side stand.

Thanks Guy's,
Some good advice there.
At the moment I am in the proccess of a top end rebuild with some goodies from Steve Maney, including alloy barrels, and CNW cylinder head.
I have tried a dave taylor head steady and the Norvil, at the moment I am using a CNW which is doing a great jub.
The problem is coming from road undulations and cross winds at high speed.
Please explain rod ends, or rod linkages
Thankyou Shane

unaproachable said:

Please explain rod ends, or rod linkages
Thankyou Shane

Click to expand...

You may want to try search, there is a bunch of info here.

G'day Shane,

Rod ends are othewise known as Rose Joints (UK) or Heim Joints (USA). Its a round bar threaded in the middle with round bearing eyes at each end. The eyes fit over a fixed peg. The rod is fitted cross wise across the top of the head (Dave Taylor design) one end attached to the frame tube, the other to the top of the cylinder head. The Commando motor shakes fore n aft. The tie rod swivel allows the head to move fore n aft but not in tension or compression cross wise. This keeps the motor in line along the frame.

The handling gets disturbed by the swing arm pushing over under corner stress, which distorts the Iso's and the furthest extent is the top of the head which leans over. The whole Iso sprung cradle therefore is at an angle to the front wheel track line. By restraining the top of the motor from side to side movement the whole Iso assembly remains relatively true to the wheel track line.

But that's not the whole story. You need to think about upgrading the front fork suspension / dampening, securing the swing arm pivot pin with 2 bolts to prevent pin shift and uprating the rear shockies. Then the tyres, always stick with matched pairs, i.e. Dunlop K81 or Avon AM26.

Mick

Thanks Mick,
Over time I have at some stage or another addressed most of these issues.
Complete new front forks with progressive springs, valve body and springs slightly modified by Pro Mecha in Melbourne, great job, felt like a new bike.
I put disc brakes on the rear, Norvil, with an 18" rim and 110 Avon, 100 Avon Front
MK111 swing arm with the cotter pins, and CNW head steady, With "rod ends" (thanks)
Although the rear tyre is 110 and close to chain guard I can still achieve a perfect wheel alignment.
New isolastics
Frame checked for straight
Wheel bearings replaced
Tyre pressures 32 rear 30 front
Triple trees from CNW
Wheels relaced and straight
New steering head bearings
Rear shocks from Icon
I have made many mistakes over the years in set up, but have learnt a lot, I think I am getting better at it.
The reason to try this 4th iso system occured to me because at the moment the engine is being rebuilt and thought I may as well strip the bike and powdercoat all the black, maybe a few mods along the way.
Cheers
Shane

Hallo over there in aussie-land I got a fourth iso built on my bike I will pm you




ps side stand has since been moved These pics were taken before the last rebuild

unaproachable said:

The problem is coming from road undulations and cross winds at high speed.

Click to expand...

Shane, It sounds like you've got all the right stuff. You might want to give these guys a call.
"Smart-Arse" Technologies
Greg - 011-61-2-9743-8466
gmd123@bigpond.net.au

They are in Syndey. Computrac can help you to make sure you have all your ducks in a row.

This is the site from the Boston franchise, it has some good info on the process. In the end, you are dealing with a very flexible frame.
http://www.computrackboston.com/

lynxnsu said:

Hallo over there in aussie-land I got a fourth iso built on my bike I will pm you

ps side stand has since been moved These pics were taken before the last rebuild

Click to expand...

After seeing another picture and this one (I wouldn't want to put another Iso on the frame) I wonder how much benefit it would be to box the cradle as much as possible? It doesn't seem like it would take much work as opposed to engineering another Iso or even installing heim joints.

swooshdave said:

After seeing another picture and this one (I wouldn't want to put another Iso on the frame) I wonder how much benefit it would be to box the cradle as much as possible? It doesn't seem like it would take much work as opposed to engineering another Iso or even installing heim joints.

Click to expand...

Dave, is this based on anything in particular? The cradle and the frame are distinctly different issues. Add how they are connected and you have three plates in the air at the same time. :mrgreen:

bpatton said:

swooshdave said:

After seeing another picture and this one (I wouldn't want to put another Iso on the frame) I wonder how much benefit it would be to box the cradle as much as possible? It doesn't seem like it would take much work as opposed to engineering another Iso or even installing heim joints.

Click to expand...

Dave, is this based on anything in particular? The cradle and the frame are distinctly different issues. Add how they are connected and you have three plates in the air at the same time. :mrgreen:

Click to expand...

There is no such thing as distinctly different issues when it comes to solving a problem with a connected system. In my example, you are trying to limit flexing in a flexible system. When the swingarm moves to the side we assume that the side play in the Iso are taken up first, and then if that isn't sufficient either the swingarm flexes or the cradle does (pointing out the the cradle is secured at several points by mounting through aluminum of the gearbox and engine). With some simple boxing (again looking at cost/possible benefit) you may eliminate one of the possible points of flexing.

Just internet hypothesizing, don't spin on it too much. :mrgreen:

swooshdave said:

There is no such thing as distinctly different issues when it comes to solving a problem with a connected system. In my example, you are trying to limit flexing in a flexible system. When the swingarm moves to the side we assume that the side play in the Iso are taken up first, and then if that isn't sufficient either the swingarm flexes or the cradle does (pointing out the the cradle is secured at several points by mounting through aluminum of the gearbox and engine). With some simple boxing (again looking at cost/possible benefit) you may eliminate one of the possible points of flexing.

Just internet hypothesizing, don't spin on it too much. :mrgreen:

Click to expand...

Who would have thought it's as simple as that. :mrgreen:

unaprouchable pm send

Hey Ho Nortoneer's,

Maybe I can leave food for thought on Isolastics and handling
as its my main interest in a Commando as best cornering instrument.
Does pilot and chassis have to endure vibration for premo handling?

Reviewing the extra iso's history - they have appeared at top
and below and reports say they help but do transmit vibration
into higher frequencies than just two standard ones. Alignment
brings up swear words to read the fine fittings required.

When 1st tried dampening occurred at 6000, so they cut
rubber width in half to lower the threshold, then in half again
till 2300 threshold of smoothness attained.
Adding extra isolastic rubbers tends to move isolation threshold up into buzz.
If they don't then they aren't really taking up their share
of chassis twist or engine bounce, so why bother.

Another common report is the more iso clearance is tightened
the better the road control but more buzz till frame cracks.

The two conditions that I feared most with unsupported
standard isolastics was high powered decreasing radius
sweepers and flat tire compensation type fork action.

I find the Rosie jointed Helm's links to be the cat's meow.
Smooth and sure footed.
Top link takes out some wind buffet on cruise and raises
isolastic fish flop threshold a few more mph in loads, but also
lets fish flop onset at higher speed and scarier higher
freq. wobbles to deal with suddenly. I made the first
of these to find it workable w/o vibration transmission.

I find the front link of Bryan Tyree to be even more helpful taking
out the fork and chassis oscillations and hunting on road texture
and wind gusts in cruise and adds even more speed and loads
before fish flop onsets at an even higher frequency
and more suddenly to limit fun and deal with in time.

I am flabbergasted by Bob Paton's low rear linkage.
It alone seems to have solved any hint of or ability
to onset isolatic or other Commando innate upset faults.
Rear by itself, one still feels the road texture hunting of
forks bothering and the jiggle wigges of wind eddies -
But rear link allows as hard of riding as you dare w/o upset
by wobbles, tank slappers or uncontrolled traction loss.
Scary delight not having to worry about speed and power just
blind hazards.

Put all three together at once and a Commando feels
like huge inertial mass of a Goldwing at criuse yet stickable
flickable as a supermotard trails bike. My experiments
imply links as far away from iso mounts the better. Trick
with rear link location is to keep center stand or not.

Then the forks must be modified to take advantage or they twist
untwist like rubber rods both delaying and magnifying inputs.
But the rear link seems to allow enough chassis twist and untwist
to take up tire vector conflicts plus plants rear enough that
extra power in fork straining turns can unload or even lift front
out of trouble before rear loses grip. Back link Invites farthest leans
in G glee.

I have my own measurements of what a Commando
motor and chassis are doing under high loads and it differs
from the obvious common sense.

Safe Journeys
hobot

Hugh :?: must be too late for me, can you translate that :?: Are you saying all heim (rose) joints are better than what came from the factory :?:

Jean

Jean, I believe the answer to your question is:

YES. (without the additional translation)

Glad to see Hobot talking about this. He has put thoughts on this for many years. It was he who first showed me the way on the front end kits I build. He has conferred with people all over the world. He has tried and failed all kinds of modifications. He lives in a motorcycle paradise except for the deer. He has broken all the parts on a Commando many twice and is worth reading twice. I have checked out some off his crack pot ideas and some of them work. At one National rally he had three major failures that keep us all working many hours good thing about the moon shine. Don’t let him near a drill though.

ludwig said:

We have a poet amongst us !

Click to expand...

Hobot's posts on the NOC list are legendary, I'd say.... :wink:

but his plea for tierods makes sense .

Click to expand...

Not in the mix IMHO: The tierod moves on a sphere whereas the ISO should move on a plane - mixing them only works because of the inherent flexibility of any structure.

To me it's far better to have EITHER three Isos (front, rear, head steady as in the original concept) OR four rods. Why four? Very simple: If the engine cradle is not linked to the frame at all it can move in six direction aka DoF. Every rod takes away exactly one DoF so four rods at the right places (similar length, parallel and evenly spaced etc.) will allow the engine cradle to move in a way which is almost a X-Z-plane as the ISOs are allowing (Actually it is not a plane but a deformed sphere with four rods - if you think about it a few seconds you'll see).

The only problem is where to mount them. The head steady is already solved so there would be one at each STD iso location. The fourth could be below the cradle, ist just needs to be installed in a way the frame can cope with regarding the forces.



Tim