Home made Butt-steady

I think the isolastic system, if well adjusted, gives a reasonably ridged frame. The head steady is definitely the weak link and deserves attention first. After that, the rear isolastic "butt-steady" is the most critical for maintaining alignment since a given side force on the rear suspension has about twice the force on the rear Iso as the front Iso.

With that in mind, after the head steady, my next suspension project was a rod-link "Butt-steady". I wanted it as close as possible to the rear Iso and dead parallel to it. I also didn't want it to be visible. The right side is anchored to the frame through existing bolt holes and the left side to the engine cradle through drilled holes in the engine mount plate.



The link is not a turnbuckle. Both ends are right hand threads, so the length does not change if the barrel is turned. The length is adjusted before installation and fixed once the rod ends are installed on the mounts. The mount on the left side is threaded for the 2 bolts that mount it on the engine/gearbox mounting plate.




Mounted, view from left rear


Mounted, view from right rear


View from drive sprocket side. There is very little clearance between the mounting bracket and the O-ring chain, but this maximises the length of the control rod to provide the best geometry.

As expected, the Butt-steady had no effect on vibration. She is very smooth at any riding speed, But my local roads limit me to 90mph.

As a barn bike, she was a hinge-in-the-middle Flexiflyer. Replacing the tired isolastics and fitting new TT100's made a huge improvement. Adding the rigid headsteady and the Hyde fork brace was a smaller improvement. Then the Butt-steady gave the last 5% in improvement. She is now rock-steady in bumpy corners and I have lost incentive for the final project: a rod steady for the front Iso. With stock rear shocks and rebuilt forks (progressive springs) I have no complaints about the handling or dampening. Does anyone have suggestions for further improvements?

nice!

One of the poorest elements of early commando frame design was the single bolt that secures the cradle's swingarm pivot shaft. The shaft and tube are not well secured by only a single bolt. The later cradles had 2 nuts on either end of the cradle tube to lock the shaft solidly in place. There's a simple modification that can be made to the single bolt tube to eliminate any play. It's called the kegler modification and it looks like this:



not-another-spindle-thread-t5978.html

I did this modification to my cradle and it helped cure that "hinge" feeling in the bike's handling... The parts can be bought at mcmaster-carr.... I did the modification by removing the rear wheel, unbolting the rear shocks, and the swingarm dropped out of the way. I used the bolted up collars, some guys weld a pair of nuts to the tube to do the same thing

Jim's spring mod and Ludwig's engine cradle pucks...

well done manxman, I like the location that you chose, instead of fouling the center stand, thanks for posting the thread and pics.

o0norton0o said:

nice!

There's a simple modification that can be made to the single bolt tube to eliminate any play. It's called the kegler modification and it looks like this:

not-another-spindle-thread-t5978.html

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Great idea. The link you provided has excellent photos and drawings. It's on the workshop list for next winter.

Manxman

When Bryan Tryee and Bob Paton pioneered rod links they worried rod would transmit vibes so went to some lenghts to get the radius length long as possible and I did too on range of ~5+ inches but none of the others using an inch or more shorter seem to notice a vibe issue so simplies DIY versions. Tryee breast support was the 1st known link to solve his Calif. grooved freeway commute wondering/hunting and did. There are two levels to tame Commando, one just taking the rubbery rebounding out and then the frame tubes/swingarm. Paton calc the rear link could see up to 350 lb leverage if pressing to tire traction break free and when he told me he could toss his over in shar pMt. bends and relax grip on bars and just use stable body english to keep angle of lean and radius of turn going - it sold me to try a rear one first. Concepts vary on wether the links work better close to isos or far away but can fully attest far away allows frame twisting loads being able to hold as must tension as ya desire, like a sling shot bands, to ease off w/o firing or to let go of bars and throttle an instant to release the frame energy fast for litteral sling shot change of hooked up direction in spots where every other cycle is in worse traction condition to accelerate or slow or change dirrection, so instead of an optimal apex point racers aim for each time, they are about anywhere in turns and more than one per turn too. The difference that has sent me loopy is all other cycles are slowing down to turn harshly sharper as in decrease radii but Peel which invited throttle snap downs into turn and sideways wheelie through and out of them and no human speed nor power can move forks that fast and hard only pure engine power and cycle frame whiplash directed crashing just right. This is WAY beyond sane operation though and only experienced in crisis rescue or statifying death wish for the thrill of it. The front link is the easiest to do and will be noticed nicely, if ya can even imagine better so be restless til ya do. I order Peel link priority as 70% low rear rump rod, 20% breast support and 10% head link. Trouble for me is it made raw off road handling so improved and road race so boring relaxed easy I decided on knobbies as best bang for the bux and good enough for the pavement flings in public hazrds, Two big cruiser ridders died on our more open clear hwys this week just behaving normal, one hur a PU that pulled out and 2nd hit a tractor just over a crest... If ya do not see cycles as a blood sport then ya just ain't experienced enough yet. If/when the swivle joint type ends wear sloppy might consider the Lords Elastometric versions as more often enjoyed than severe load handling was the uncanny disappearing act of Peels deal. Play with your iso gaps as might be able to open some for sooner deeper isolation w/o loss of confident handling. Need time in rear iso add a couple more big cushions too. Paton stuffed 6 in his and loved it and stayed centered longer.

Snorton74 said:

Jim's spring mod ...

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I assume the rational for the spring is to take "engine weight" off the isolastics so they don't sag with chronic compression. If your bike is usually parked on the centerstand (as mine is), the load on the Iso mounts is in the opposite direction, and much much lower load since virtually all the drive train weight is going directly through the cradle and centerstand.

Of course, if you use a rear axle stand, the side stand or a frame-mounted centerstand, the Isos are still compressed when the bike is parked.

Manxman

Snorton74 said:

Ludwig's engine cradle pucks...

Click to expand...

very clean design. Wish I'd though of it.

The puck is about 10" away from the rear Iso and and even farther from the front. If it's job is to prevent movement from a sloppy Iso ( a perfect Iso would have no slop), then which one is it supposed to be backstopping for? Ideally, an accessory steady (rod or puck) should be as close as possible to the Iso it is backing up, one for each Iso. If it is half way between 2 Isos, it is subjected to 2X the loading and allowing 4X the displacement. It is also potentially transferring additional load to the remaining Isos and wearing them faster.

The Iso system has 3 fixation points in a 18" isolateral triangle. Good engineering behind that. (I wonder if the "ISOL" in "ISOLastic" comes from "ISOLation" or "ISOLateral" ?) If we are gong to replace the locating function of the Isolastic design, the new locators (rods, pucks, whatever) should either maintain the same geometry or duplicate it completely in another orientation.

Manxman

There already is a front steady from Windy (bill on this forum). I have one on my bike and it does help some.





I almost prefer hobot's "rump rod" name to butt-steady though.

Manxman expand your geometry concept of linking frame/cradle *beyond-outside* of the 3 point mount triangle rather than withing/between isos and thus also making the triangle distorting resisting leverage legs longer-wider. Road loads are patch to patch pivoting in cradle area so think of where to grab a 5ft long teeter totter for best damping. One of the most educational experiences for me was Wes and my 1st Cdo with loose-worn everything was grabbing rear patch side side to see it show up most in side/side motion at front iso gap. That when it hit me that the weave/wobble onset (w/o frame twisting loads) was the tail end slapping the front gap then forks silly a mm or so, which at some speed is way too much play on direction oscillation changes that can build up fast. if swing arm and tranny bushes worn enough even the triplex chain bouncing tugging rear back into front gap can onset hinging going straight steady 50-60 - which I could not reproduce on purpose but worse if hands off. Everything matters in something as complexity simple as a isolastic Commando.

Good way to go by tying the frame tubes together and not bad idea to tie rear frame and cradle cheeks together too. Comnoz passes his front link through the front mount plate so out of sight but close inline with isolastic which does not tie the over lap of cradle and frame as well as links out beyond isos but may not matter unless getting into crisis.

batrider said:

I almost prefer hobot's "rump rod" name to butt-steady though.

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I must agree on "Rump" over "Butt". "Butt" is too reminiscent of Rap lyrics. "Tush" and "Fanny" are too trollup-like. "Arse" isn't even a contender for a gentleman's Roadster..

Now the fun part: picking a name for the front steady. The floor is open for suggestions. Gentlemen, start your engines.

Manxman

Ms Peel called front link her breast support though chest would be more polite in mixed company. Rump term has more whole rounded muscle area of a horse while butt seems a bit too targeted to me and no one I know feels comfortable on rod term being used back there so open to semi crude non sexual term. Control as 2nd term following any location name would be politely understood but just not Rocker rough & ready enough for me.

Btw I rode Peel with only one link hooked up at a time to access and also left the lock nut or lock wire off for intervals to see if radius rod would vibrate to a better or worse condition than set neutral so a dash of slack state to find either expanding on contracting tension would buzz bomb me. Seem tricky tedious to set ends neutral slack off the bike so keep in mind if sensing buzz in some loadings. Ya do not need curves to test isolastic stablity just zig zag in you lane tighter and tighter with a bit of throttle jab at instants of switch backs till snese of hinge onsets or not, with and w/o the link. Especially stressful skill if tire air is on low deforming side. Its stupid as shit and scary and almost crashes me on un-tamed Trixie about 35 mph but freaking Peel would start lifting a tire front or rear about 45 before too crazy for me. More than anything else is the extra security tamed isolastics offers.

I have had to actually jerk around like this a number of times, once closed in behind an entering 2 ton dual tire flat bed slowly accelerating up a steep about 10 bike lengths back so no thought of brake in time or worry about stuff falling out of bed when a soft ball size stone slung out from tires about 45 mph so had to jerk half a lane over to dodge. If normal cycler close Id been hit hard. Small animals darting back and forth confused for last instant missing, pitching into a blind turns pretty hot to see wash out ruts, mud streak, pot hole, vehicies, limbs, plywood, chicken guts, diesel, school bus, elk, ATVs, or corner cripple sports squad to zip around. I think I finally figured out why so so many small animals, bird included dart out so close so routinely, they know cars stay on the road & not too hard to judge a dart past but safer as car scares away the predators in that interval so worth the risk exposing in open road. Some times surprise vultures to bald eagles of huge turkeys that launch along road as trees blocking the side escape so end up almost right under them to jerk fast as I can off ~4 ft out of line as surprised birds use JATO assist of hot poopoo jets to lighten load and fluster anything following that close. Now ya know the real reason birds do not fly in single file but a V... Trail braking may be the best for racing and everyone gets away with it but I will never develop that habit after above so always full up right more than enough ahead of time.

Hello manxman, nice Butt-steady you made. After installing it, do you still use the vernier caps for the side clearence or can man simply take them out and leave the side forces to the new steady only ? Thanks for your answer.

manxman - can you supply a part number and source for the heim joints? I tried a couple from McMaster, but they very quickly (like <100 miles) developed slop in a headsteady arrangement. The old girl pounded them to death - maybe its a form of organ rejection....

You're solution looks great! I like it doesn't foul the center stand.

Thanks!

nortontvr said:

Hello manxman, nice Butt-steady you made. After installing it, do you still use the vernier caps for the side clearence or can man simply take them out and leave the side forces to the new steady only ? Thanks for your answer.

Click to expand...

The bike has non-adjustable isolastics. I have just ignored them. The arc-shaped geometry of a radius rod is wrong for the linear sliding of the Isolastic system. There is no way they could be set up for zero clearance on both. I assume they will both wear down until they give each other a bit of slack. Kind of like a marriage.

Manxman

napanorton said:

manxman - can you supply a part number and source for the heim joints? I tried a couple from McMaster, but they very quickly (like <100 miles) developed slop in a headsteady arrangement. The old girl pounded them to death - maybe its a form of organ rejection....

Thanks!

Click to expand...

These were sourced at considerable di$count from an un-named engineering company's "Skunk Works". When they need to be replaced I'll likely look to an aviation supplier.

The Commando is not my daily ride, so I haven't worn out the joints yet.

Manxman

Peels helm joints did not get used long enough to wear for me to notice so ask what is noticed by those whose have worn? Missing center stand is definitely an advantage of your higher mounting. I am totally taken aback by how secure Peel became with the links but did miss the center stand so maybe swash plates would solve everything back there for what I think is going on risking life/limb for kix. I had a pretty good sex hound era but its Peel road organism I linger on the most.

hobot said:

I had a pretty good sex hound era but its Peel road organism I linger on the most.

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Thanks for sharing :wink:

I was told that Peels set up should be limited to being described as a Watts like cradle linkaga via helm joint radius rods. Peel rump link is made over robust so no give at all but the breast and top control both have a few inches of long bolt extension so gives sides ways at high side loads but for the life of me I could not on set any upseting springing oscillations. All other cycles loose it on my jerky style but Peel freaking ate it up. I never found a limit but enough loved to turn regular bends into decreasing radii for the breath taking feeling of cheating death and cycle physics. Maybe someday we can get slo-mo video of Commando motions in various places with and w/o links.
Grab a Z plate and tug on it observing why it moves some even by hand, ugh. Oh yeah, I was able to induce some Peel weave/wobble with only front and head link attached, no rump rod, still better than untamed but not transforming for the toe curling mufti-orgasms. I forgot the names of one night stands but not those worth a second and 3rd flings.