Isolastic Links

We all have most likely seen the aftermarket top mount that uses a Heim-end link rather than the muffler rubbers, but has the same thing ever been applied to the iso mounts? As many threads as I've seen (proper shimming, which washers to use, running the MkIII vernier adjusters), hasn't anyone built a Heim-end link for the lower isos that would completely eliminate having to shim the mounts? With this, the centering load would get carried by the Heim joints alone, completely removing any side-load from the isos themselves. It seems like H-D uses something similar on their rubber-mounted engines. Thoughts/ideas/links? I'm getting ready to perform a major R&R to my '74, and would like to see the options out there.

Nathan

I'm sure one or two forum members have put rod-end links at the three iso mounting points, but the rod-end links are addressing the symptoms not the cause. Get your frame etc aligned properly and you'll know where the frame centre line is and the swingarm/steering head axes relationship will allow the swingarm/rear wheel to move parallel to the frame centre line plane. You wont have any handling problems and it's also less work.

Cue drivel from the usual suspects with references to hinge, imaginary 0.001", camber etc ad infinitum.

NP, in short your are wanting the make the driveline "rigid", left to right, and allowing movement up and down via heim joints... ??????.. Is that what your asking???

Rigid mounted is not out of the question. There are a few on here who have done it eg featherbed blue Norton in OZ, seely race bike in OZ and maybe more, And they dont suffer ill effect from ....................... " Get your frame etc aligned properly and you'll know where the frame centre line is and the swingarm/steering head axes relationship will allow the swingarm/rear wheel to move parallel to the frame centre line plane. You wont have any handling problems and it's also less work."..........

I cant quite picture want and how you intend to achieve this, but IMO heim joints as lower "engine mounts"....... nup ... but i could be wrong with out further info..

olChris said:

NP, in short your are wanting the make the driveline "rigid", left to right, and allowing movement up and down via heim joints... ??????.. Is that what your asking???

Rigid mounted is not out of the question. There are a few on here who have done it eg featherbed blue Norton in OZ, seely race bike in OZ and maybe more, And they dont suffer ill effect from ....................... " Get your frame etc aligned properly and you'll know where the frame centre line is and the swingarm/steering head axes relationship will allow the swingarm/rear wheel to move parallel to the frame centre line plane. You wont have any handling problems and it's also less work."..........

I cant quite picture want and how you intend to achieve this, but IMO heim joints as lower "engine mounts"....... nup ... but i could be wrong with out further info..

Click to expand...

olChris, that's exactly right. My intent is to allow the iso/engine to vibrate in the vertical plane as intended, but use heim joints (or equivalent) to restrict the side-to-side movement in lieu of the teflon washers taking the load. That way, there's no hassling with keeping the clearance just so, and (theoretically) no slop. My intent is not to side-step any frame alignment issues, but more to see what a zero sideways wiggle with unrestrained vertical would buy me. I don't want to go rigid, as the bike is regularly ridden semi-long distances, and the iso action sure helps take the edge off the vibration.
Nathan

Somewhere here in the last month-or-so somebody posted a few "racing" mods they did to there race bike... Included was a buffer/restrictor device that were adjustable to maintain the position of the cradle at the swing arm area, which would greatly reduce the "play/drift" allowed by the rear iso joint... Which in turn would reduce side to side pressure on the Iso's. therefore reducing wear on PTFE washers and maintainence.

It/they (one each side) was fixed to the frame and held tension onto the cradle via "teflon" ?? pads to restrict swingarm side-to-side play.........

Im sure someone will recall the title of the thread and hopefully post a pic for you...

GrandPaul shows a picture something like what I'm thinking of. There's a nice shot of it about half-way down the page at http://www.accessnorton.com/norton-880-long-term-project-t2779-135.html Still waiting to hear back if they make one for the rear.

olChris said:

NP, in short your are wanting the make the driveline "rigid", left to right, and allowing movement up and down via heim joints... ??????.. Is that what your asking???

Rigid mounted is not out of the question. There are a few on here who have done it eg featherbed blue Norton in OZ, seely race bike in OZ and maybe more, And they dont suffer ill effect from ....................... " Get your frame etc aligned properly and you'll know where the frame centre line is and the swingarm/steering head axes relationship will allow the swingarm/rear wheel to move parallel to the frame centre line plane. You wont have any handling problems and it's also less work."..........

I cant quite picture want and how you intend to achieve this, but IMO heim joints as lower "engine mounts"....... nup ... but i could be wrong with out further info..

Click to expand...

To put olChris's comments into context. Criticism requires analysis, in this case through riding a motorcycle preferably before and after modifications. By his own words, olChris has virtually zero mileage and technical experience when it comes to Commando's. Yet in his own mind he's apparently become an expert on the subject of handling over the last 4 months since joining the forum. Typical of quite a few who can talk a good rebuild without backing it up with mileage. I've personally covered 137,000 miles on my bike, over the last two years 16,000 miles post frame alignment.

There is a picture of a rear Heim joint setup on the forum, maybe in one of Ludwig posts, it used mounting points on the gearbox plate and the main frame using the x member as the attachment point. You could try running the iso's with no clearance but the frame breaks so restricting the movement to a strict plane is an improvement, a good headsteady along Lugwig's lines and the MK3 ISO suspension spring all help.

bill-from this forum has one on his front mount. Works well from what I've seen of it.

Found these on the PC, not the setup I remember and they will wear out quickly unless protected.

I strongly recommend that this example below not be followed.

In the example shown in the pictures below, the heim joints are placed in a bending moment; this is not what they are designed for. The heim joints should only be used in tension or compression along the axis of the treaded fitting. Generally, threaded fixtures are not meant to be placed in bending moments.

Furthermore, the brackets welded to the frame are placing the frame tubes in torsion.

kommando said:

Found these on the PC, not the setup I remember and they will wear out quickly unless protected.

Click to expand...

Al-otment said:

I'm sure one or two forum members have put rod-end links at the three iso mounting points, but the rod-end links are addressing the symptoms not the cause. Get your frame etc aligned properly and you'll know where the frame centre line is and the swingarm/steering head axes relationship will allow the swingarm/rear wheel to move parallel to the frame centre line plane. You wont have any handling problems and it's also less work.

Cue drivel from the usual suspects with references to hinge, imaginary 0.001", camber etc ad infinitum.

Click to expand...

I agree Al getting the ISO points wheels swinging arm pivot and other things to work as they should is most important part of getting your bike to handle as it should. If its all lined up as best you can then wear an need for adjusting should be minimized and with later type vernier adjusting mounts it is not such a big deal.
Riders weight position an riding style also can have an effect on handling see the weave an wobble thread.
The mate I ride with has a 2003 Honda fireblade we don't hang about an I know my Commando is no match for his bike but I has never misbehaved as I chase him at speed that would get be in big trouble with the law.

About the full range of linkage's has been tried already and the results are in. Comoz tried using link close in line with the isolastic and is now spending almost as much as me on a smaller displacement lighter piston engine to get back the smoothness. Ya can not use the links to help isolate the gaps only to prevent frame rebounding with normal set gaps. Peel gave bad vibes if I let the rod links find their own tightness or set them with no slack -ugh. Everyone else also trys to mimick a solid frame by making the top and front rods or swash plates robust w/o compliance, ugh. Much as the clunky big heavy rear triangulated rump link may offend some that's the main-most effective place and way to try to mimic a solid frame cycle's swing arm to frame stability. Only one example of tri-linked 2/3 rds wimpy forgiving links, all very far away from iso's for best resisting leverage, so only one knows how Flabergastingly Fabulously smooth and secure a C'do can be over the current buzz bomb jitter bug corner cripple. I no longer think of shooting up, snorting up or screwing with others' women after the flings on Ms Peel I could not feel under me but her orgasmic road moves. Best wishes getting as hi as I have on a rubber baby buggy.

Bob Patton has this offering:

pictures-rod-linkages-t17632.html?hilit=link#p219451

Doug MacCrae has this offering via Herb Becker (no heim joints):

race-commando-handling-secrets-revealed-t9553.html#p106032

And Ludwig has his own version sans joints:

300-lbs-commando-t18186.html

This has been my front mount for many years. Maybe I will get the rear done this winter. Jim

The elite cycle designers are struggling to build in some lean load tire conflicting compliance which my current hero Freddy Spencer stated in magazine interviews last year, the attempts have mostly failed d/t parts being too weak to control the loads or break under the loads. You could weld the engine and cradle and swing arm to frame at the isolastic mounts to end up vibe'd to death and wiggle wobble off path by wimpy thin frame tubes rebounding yet there is pure magic lurking in the ingenious isolastic set up if ya can tame its rebounds w/o restraining its surprising buttery smoothness like tensing and relaxing a rubber band instead of a bow string. Herb Becker and Ludwigs rub plates may be a improvement to add or replace the various rod links but notice they are not near the isolastics... Try as I might and paying big bucks to find out - no way can the solid-rigids even on balloon tires stick and take harsh corner loads I'm addicted to now w/o feeling presence of a cycle under, only seat pressure, wrist strain and blood pooling - erriely similar to my times in soar planes doing loops and spins with only wind buffet getting through the G' forces.

A few more factoids to consider in taming a Commando. When rode ordinary Trixie w/o head steady I got across THE Gravel and 15 miles down easy turns on highway 65-70 mph when came upon a nice level S section so let us drift across the double yellow - to remain more up right cutting corner just being lazy to instantly be fighting THE Hinge for many yds till testicles descended again and carried on way Way wiser about how vital head steady is to un-tamed isolastics and how little its noticed otherwise. On Peel with rump link below and behind rear iso and breast link above and forward of iso sort of Watt's like linkage I rode far and hard w/o head steady no surprises secure, once installed only thing that disappeared was the wind buffeting off forks that I too once thought like everyone else, was just road texture getting though, nope. About most exciting thing to occur in my life last decade was tri-links so hope others find similar satisfaction one way on another.

The less welding and elaborate fabrication, the better (in most cases).

The front steady referenced in the link to my post is a bolt-on, very simple appurtenance, and works exactly in the manner required to limit the front iso to it's most effective range of motion (as do the top heim/rose joint units in their respective position).

I don't recall seeing such a simple, bolt-on solution for the lower/rear.

I have always maintained that triangulating a set of lateral-limiting links (as close as possible to the isolastic points) should be the ultimate solution to taming the isolastics.

grandpaul said:

I have always maintained that triangulating a set of lateral-limiting links (as close as possible to the isolastic points) should be the ultimate solution to taming the isolastics.

Click to expand...

The iso's don't require taming. This is a misconception which has been perpetuated ever since it was realised that some Commando's didn't handle as well as the Featherbeds.

I've asked this question before - and still none of the isolastic critics have answered it - how come Peter Williams on the Monocoque averaged 105.47mph during the 1973 F750 TT win using iso's and averaged 96.53mph on the proddy racer Commando using iso's, finishing second to a Triumph but also ahead of a Triumph in third during the 1972 production TT?
The Isle of Man today is a bumpy road circuit at legal speeds, god knows what it was like 42 years ago at race speeds.

Its not the isolastics per say as much as the whole frame twisting from stem to stern with rebounding merely aggravated by the cushions' compliance and slack. The monocouqe obviously didn't suffer much or any rebound so could keep adding conflicting tire side loads till they let go to road ski-drift and hook back up w/o whiplash into hi side. My impression on Peel was the frame twisting allowed the tire conflicts of road texture to pass through in waves w/o resisting the tires while at same time could steer sharp enough to hold some twist in frame for better tire cooperation angles, so could keep in 'full' traction longer-harsher before a patch or two lets go to begin the skiing sensation - if ya into the sort a thing for fun. Peel sure falbergasted me when I'd try stuff i learned on SV650 and 900 Ninja but nothing happened except sharper turn on power with rather less pilot attention/effort, so gritted teeth to press harder and harder and still nothing bad happened at but hooked around even faster with distinctly out of square motion of hand grips to the foot pegs, which is where i felt/noticed the motion the most. When I'd try to put such loads on the moderns they'd resonate-hum-buzz to suddenly jerk a tire out, no easing into it possible. Same shit that catches real racer out by surprise. Only way to get past the surprise skip outs and jerk down or flings up was to go in like a flat tracker - unless in town sections of IOM or Mt. or Gravel sections here there is no room to ski out ward, so pretty much taboo to me and essentially impossible to slide-drift Peel on pavement unless i intend to on purpose for a slower wider lazier way around when room and mood to do so. On THE Gravel its second nature to let any cycle get slightly skewed or give a bit more throttle spin to drift outward some to ease lining up with the changing exit of turn or enter another the other way. Kan't ignore the tire profiles and traction compounds as concerns what the frame needs to handle. Looking into history shows the biggest game changer in mc racing was tire improvements that then required frame and suspension improvements, not the other way around. If ya got a tetter tooter diving board to tame ya don't grab it near its pivot point...