tweeking the steering head

I have finally gotten back to straightening the frame on my '70 Commando. The idea is the get the wheels closer to operating in the same plane. I'm not looking for the WSC. At 4' a rod through the steering head was 7/16" off center ( ~1/2 a degree ).

I pulled the steering head over ala olChris. It worked great and really did not take that much force ( less than one ton). Now I'm looking for ideas on how to fine tune the position of the steering head in relation to the isolastic centerline . Please note that the webs on the angle iron that I used to establish the centerline varies in thickness by 0.002-0.003" and I do not have vast slabs of flat granite or much in the way of machine tools.

My goal is to keep the bike from wobbling after passing a semi or some such thing. It has always been fine going around corners.

Thanks

Greg

Sounds like "7/16" off center and ~1/2 a degree" are not even in the same measurement league ?
I'd doubt they were even built to 1/2 degree accuracy ??
And you say you have straightened it since then - how close to you want to get, given you say you can't measure it that fine...

Jist thought we'd ask before doing anything irreversible.... ?

"wobbling after passing a semi " has more to do with the aerodynamics, or front forks rear shocks ?
Thought of trying a different jacket or helmet ....

I just worked out the tangent for 7/16" at 48" and came out with 1/2 a degree (0.522212696 to be more precise). It has been a while since I had geometry but I think that is how it is done. I'm sure that I can get it better than that, but don't really want to spend a lifetime making a silk purse out of a sow's ear. Besides, like you said, I can't measure it that close anyway.

It would be nice to get it within the tolerances that I can measure, maybe 1/16" at 48" from the steering head. As far as what tolerances they used when building them, I can't say, but I'd hope they kept the front wheel in line with the rest of the bike.

I can be well in front of the truck and rolling off the gas will make the bike wobble. Getting back on the gas will usually help. Or weaving around a little settles things down too. A new rear tire always does the trick... As I had mentioned before, it has always been fine going around corners. Oh and I'm usually touring so I have saddle bags and a load of camping gear. Nothing has worse aerodynamics than a motorcycle.

Merry Christmas you you and yours. I have to get going and open some presents before the Missus thinks I have been on here too long.

Any ideas would be appreciated.

Greg

Its the whole C'do sackness showing up. As stated just straightening will not help wind buffet wobbles, only fitting decent tires and getting slack out of gearbox/clutch and swing arm spindle via collars and some attention to position - posture on bike during wind buffet. To get rid of the wind buffet is similar to what it takes to stifle wobble-weave-hinge on powered fast lumpy sweepers and when done right drafting semis and flinging around em while another semi passes near by the other way is calmly thrilling.

gjr said:

I just worked out the tangent for 7/16" at 48" and came out with 1/2 a degree (0.522212696 to be more precise).

Click to expand...

That degree is correct.
That is a reasonable amount,around 1.5 over the length of the steering head tube and some 6.5mm at the axle.
The only way to accurately check a frame (short of a machinists level) is with a machined frame jig. (The reason I built one around 1993,all machining done on a Bridgeport with DRO )
I run my DR650 with large payloads including over 40 litres (30+ in the fuel tank) of fuel on occasion,loaded and unloaded makes for different handling for sure.

You followed all this thread, yes? strange-frame-t18084.html

I have followed the strange frame thread, but the whole thing got strange.

I'm not interested of why I can or can't do this, should or shouldn't attempt it, etc. I'm interested in 1) practical improvements for my measurement accuracy and 2) a more convenient way to get a hold of this awkward frame and bend it in a somewhat controlled manner.


Greg

gjr said:

I have followed the strange frame thread, but the whole thing got strange.

I'm not interested of why I can or can't do this, should or shouldn't attempt it, etc. I'm interested in 1) practical improvements for my measurement accuracy and 2) a more convenient way to get a hold of this awkward frame and bend it in a somewhat controlled manner.


Greg

Click to expand...

Please tell us about your skillset... about the shop/tools you have available

If my stem was twisted some, I'd nail frame down via rods through the iso tabs and block/lock together the front down tubes and put a pipe though stem and bend trial error till good enough to eyeball or crudely measure. Thank goodness motorcycles are not that sensitive to perfect alignments. My Trixie Combat was really mangled by a deer knocking headlight and rest of bike out from under me to bend stanchions sideways and stem some then landed R engine on me so hard it bent under tube to L about 3/8" and a bow in spine and left R knee dangling by skin and some remaining muscle attachments, so just did brutal things w/o any measuring to lessen the amount of extra head steady assymetric shims and spacing of front iso tabs with some machining of front mount width so two of us could with some pounding and levering could force it all back together and works just fine for smooth isolastion and handy handling even hands off [with good tires]. Your call to try for perfect almost impossible anal corrections [like sending to GT Enterprises] or down & dirty horrific hobot sytle to get back riding sooner than later. To me the smoothness and low effort to steer stable predictably is main feature I love in C'do's and Trixie delivers that again with the Combat punch to boot and have done 1000 mile days and didn't want to get off to end the trace state so smooth and easy to live on crooked as can be to assemble or measure.

Hi Steve,

I am heartened by your success with getting things more or less in line and having the bike ride well. I'm going for somewhere between anal perfection and the hobot mash it into submission.

concours,

I am fairly handy at fixing things. I put the motor in this bike together about 50,000 miles ago and have just put in 0.020" oversize pistons a few years ago. Our local bike shop handled the machine work. I have several Volvos ('67, '87, '04) that I maintain. The '04 is demanding better diagnostic tools to sort out the ABS light ( Volvo went their own way on DTC codes). I have been all through a '40 Farmall H (motor, transmission, hydraulics, etc.), various other tractors, combines, and assorted vegetable equipment. I can measure, cut, and fit to a few thousandths. I have a lathe, but have been using carbide tools since my tool grinding skills are still not 100%. My welding skills are so-so, but two neighbors are very good. I have calipers, mics, dial indicators, straightedges, a 12 T press, a decent set of hand tools, a 9000# lift in my garage...

Greg

gjr said:

Hi Steve,

I am heartened by your success with getting things more or less in line and having the bike ride well. I'm going for somewhere between anal perfection and the hobot mash it into submission.

concours,

I am fairly handy at fixing things. I put the motor in this bike together about 50,000 miles ago and have just put in 0.020" oversize pistons a few years ago. Our local bike shop handled the machine work. I have several Volvos ('67, '87, '04) that I maintain. The '04 is demanding better diagnostic tools to sort out the ABS light ( Volvo went their own way on DTC codes). I have been all through a '40 Farmall H (motor, transmission, hydraulics, etc.), various other tractors, combines, and assorted vegetable equipment. I can measure, cut, and fit to a few thousandths. I have a lathe, but have been using carbide tools since my tool grinding skills are still not 100%. My welding skills are so-so, but two neighbors are very good. I have calipers, mics, dial indicators, straightedges, a 12 T press, a decent set of hand tools, a 9000# lift in my garage...

Greg

Click to expand...

Ok, cool. A simple fixture can be whipped up to hold the bike. A base plate, perhaps 3/8" (minimum) to connect to, tacked to a BIG workbench, or lagged into the floor, will afford holding power. Picking up the iso holes, also grab the bottom horizontal tubes, using an angle iron or larger tube to be sure you don't mar/kink the tube. To grab the steering neck, a couple discs about the size of the bearings, minus .005" to allow a slip fit, with a stout bar ( 1" or 1-1/4") through. A big pipe for leverage will afford you the beans to yield the position of the headstock. Be patient, increase force gradually until some change is observed.

gjr said:

Hi Steve,

I am heartened by your success with getting things more or less in line and having the bike ride well. I'm going for somewhere between anal perfection and the hobot mash it into submission.

concours,

I am fairly handy at fixing things. I put the motor in this bike together about 50,000 miles ago and have just put in 0.020" oversize pistons a few years ago. Our local bike shop handled the machine work. I have several Volvos ('67, '87, '04) that I maintain. The '04 is demanding better diagnostic tools to sort out the ABS light ( Volvo went their own way on DTC codes). I have been all through a '40 Farmall H (motor, transmission, hydraulics, etc.), various other tractors, combines, and assorted vegetable equipment. I can measure, cut, and fit to a few thousandths. I have a lathe, but have been using carbide tools since my tool grinding skills are still not 100%. My welding skills are so-so, but two neighbors are very good. I have calipers, mics, dial indicators, straightedges, a 12 T press, a decent set of hand tools, a 9000# lift in my garage...

Greg

Click to expand...

No all totally inadequate, when you log in your name needs to come up in blue like all the other knowledgable Norton experts, most of there bikes run like a dream, because that's all they are

concours said:

A big pipe for leverage will afford you the beans to yield the position of the headstock. Be patient, increase force gradually until some change is observed.

Click to expand...

So far so good. It takes about 500 pounds of force on the end of a 4' long bar through the headstock to move it. The problem is that everything moves and then relaxes back. Moving the end of the bar 7/16" does nothing. Moving it 3" does virtually nothing. Moving it 3 1/2" is about 5/16" too far. I get that it is going to be trial and error, but it is nothing close to linear.

The next problem is how to know when it is lined up. I can turn down the end of the 1/2" rod through the headstock, but I don't have a good way to make the end of the angle iron into an accurate pointer. Ideas on reasonably repeatable and accurate measurements ?

Greg

Frame straightening is better done by some body with a jig plus experience. There is still only one guy in melbourne I would take a frame to, and you would not want to watch him straighten it. You could do itself if you can lock the frame down onto a piece of channel and use bars with machined cones to hold the steering head and the pivot securely in relation to one another and start measuring carefully. A magnetic base protractor is a help. Changing the rake by half a degree is about what is invloved in changing from 19 inch to 18 inch wheels without altering the handling, so I don't know how you will get the setup right with isolastics - . It is normal to put a long bar through the pivot mounts and measure to one through the steering head, on a normal frame it is not difficult. I think the isolastics will drive you mad, unless you fit them with solid bushes while you do the job. You need to set a datum.

Ideas on reasonably repeatable and accurate measurements ?

Turn a point on each end of the measuring bars, and be careful to centralise them in the frame.

gjr said:

concours said:

A big pipe for leverage will afford you the beans to yield the position of the headstock. Be patient, increase force gradually until some change is observed.

Click to expand...

So far so good. It takes about 500 pounds of force on the end of a 4' long bar through the headstock to move it. The problem is that everything moves and then relaxes back. Moving the end of the bar 7/16" does nothing. Moving it 3" does virtually nothing. Moving it 3 1/2" is about 5/16" too far. I get that it is going to be trial and error, but it is nothing close to linear.

The next problem is how to know when it is lined up. I can turn down the end of the 1/2" rod through the headstock, but I don't have a good way to make the end of the angle iron into an accurate pointer. Ideas on reasonably repeatable and accurate measurements ?

Greg

Click to expand...

Make some taper cones for the end of your rod pointer. Swap the pointer 180 degrees to verify /split error. Linear only after the yield point is reached, which is hard to discern, no doubt.

To rig up a way to visualize the out of vertical of stem to tire, drop string on bob weights in front and behind lined up on spinal center line, step back enough to view the string in relation to tube in stem, assuming the iso holes are all pretty level or square to the drop lines. How are you holding frame and applying the forces? At some point might make more sense to slice off and weld back for peace of mind. Do not expect much if any change in let off wobbles, if bike was not already a nuance running crabbed or leaned like resisting a side wind when there wasn't any. Remember that vintage video on wobble/weave onset showing every bike they tried would wobble at hwy speeds - especially if pilot was leaned forward and settled right down by his sitting up or shifting weight rearward or by adding some weight behind the pilot. I can tell my Trixies tire wear state by the speed of hands off wobble/weave onset when I let go bars to remove mad insects to jacket zipper opening from wind blast before its flapping. New tires ok down to about 30 mph, bad tires about 50. Cdo's wobbles/weaving has annoyed and scared serious uses for decades and best simple solution to my mind are the rod links, ESPECIALLY rear one. 1st link was a front one created by Bryan Tree d/t California freeway rain grooves front snatching on his commutes. It pretty easy to rig one up and likely all you need to stifle the let off wobbles. Head links also a dime a dozen DIY or off the shelf selection. But most stabilizing is the very very rare rear links and it will never be easier to rig one while raw frame in hand. What you are feeling is positive feed back build up of the whole system slackness/compliance of swing arm lightly slapping the front iso gap, to slightly twitch forks, which road follow back harder, *& on and on, Worn tires or wind eddies, pilot posture and position can aggravate. This is totally separate issue from aligned straightness nice as that is, crooked and tire out of line and non vertical tire bikes ride a bit crabbed or leaned but does not induce positive feed back upsets. Sticking stem bearings, restrictive fork travel will fight road following and pilot input opposite to expectations and can build up positively. so may end up fixing something seeming unrelated and not even know it. Oh yeah most pleasant surprise to me with the linkages was how huge sluggish massive inertial stable smooth megalithic like mine felt ignoring nullifying absorbing wind gusts, truck vacuum/buffet and road texture annoyance. This has a certain element of danger I found out too as takes so much ordinary speed sense away you better look at speedo to enter various turns or might end up testing/learning decreasing radii thrills to became insane like me wanting no cure but craving more. Btw Ms Peel would run steady hands off to a few mph with just a bit of natural fork weave to stay upright but did not escalate. I can't do that on my prefect straight solid SV650 on new tires, but does allow hands off to 20 mph before I better grab on again.

HI as this is my first post, I perhaps should say hello to all. My main bike is a guzzi but a couple of French friends have Commando's and I sometimes get roped in translating ...

There is an article floating about the interweb where the late Kenny Augustine sorted a Commando frame to the great benefit of its handling. Perhaps an adult could point us in the right direction?

According to rumour. the subcontractor who produced the guzzi Tonti frames, started on one side and just worked his way round, which would explain why all the guzzi frames I measured had a similar offset, and ping when cut. Are Commando frames the same?

Anyway, here's what I did.
I measured a guzzi frame and found a similar error to yours, about 3/8". L.S.S. - in the end I cut the head stock off and re welded it.
A "professional" had completely ruined a similar frame by heating and distorting it using brute force. None of the engine, gearbox or swing arm mountings aligned afterwards, and the headstock tubing was distorted, so I scrapped the frame. The next one I decided to do myself.
I had access to a tool room with surface table. I made up a stout pointer from a hydraulic ram with cones and used gauge blocks to determine centres. A calibrated bar through the swing arm pivots provided a horizontal datum. Once levelled, plumb bobs helped drop centres on to the surface table.
The guzzi frame is pretty easy to work on as it is made from low carbon steel of substantial thickness. So no heat treatment issues and not likely to buckle unexpected under small forces. Not a trivial job though without distortion. Although I carried a welding code then, I usually worked on much thicker material, so I was somewhat nervous on the thin stuff (stage one ignorance).
I would make sure you can measure with the required degree of repeatable accuracy.
Hope this helps.

Ugh, only Peterpan here had long pow wow's with Kennie and it was Tom Davenport of Phantom Oiler site that hosts The Worlds' Straightest Commando that put me onto the helm's joint tri-linkage kids stuff. The fella that commissioned the job was not a good customer and never really completed WSC to road worthy state to test while in Ken's possession and who ever ended up with it wasn't much a rider who could tell anyway, just a bargain from the poor original customer with many distractions that made Kennie both pissed off and could care less about it. What Ken did care about -for a while- were the isolastic C'do racers he built and had riders race successfully. He' didn't have that much respect for isolastics or even the Norton engine but said they'd out handle that era's cycles once he shortened wheelbase by taking up space between engine/gearbox. So I repeat take me as a buffoon or just pointing out sad factoids, fine fit and alignment are always best but in a mass produced isolastic forgiving Commando just getting things close enough to assemble well works same as perfection road handling wise. Which is like my number one motivator in fun life so not trying to mislead anyone but leave em grinning like me each ride fast or slow.

On my poor deer splatted Trixie I got some cyclic buzz on initial recovery rides to find head steady was shimmed enough extra sideways ok but front to back and vertically rubber cushions were straining till too taunt or too compressed to isolate hi freq. I put the ole hobot heave ho to er and been sweet as the as the easy gal next door ever since. To me fretting about the perfect Commando and getting it ...is like Lilly Tomlin quote, "When ya win the rat race, Ya Still a Rat!"

Master metal massage'r having at it - do not try this at home kids, but can have a laugh on me til I got those rubber cushions looking real relaxed. Oh yeah what is moving is the re-enforced-bridged plate type head steady fastened to head, for a sense of how stable a foundation we got to work with. Did it single handed. There's at least 3 other areas I found on frames moving a silly mm or two with surprising low force just where ya least like to see it, ugh. Move your forks a silly mm at speed for sense of the springing forces to tolerated or not.
[video]http://www.youtube.com/watch?v=4mm7tyrK350[/video]

concours said:

gjr said:

Hi Steve,

I am heartened by your success with getting things more or less in line and having the bike ride well. I'm going for somewhere between anal perfection and the hobot mash it into submission.

concours,

I am fairly handy at fixing things. I put the motor in this bike together about 50,000 miles ago and have just put in 0.020" oversize pistons a few years ago. Our local bike shop handled the machine work. I have several Volvos ('67, '87, '04) that I maintain. The '04 is demanding better diagnostic tools to sort out the ABS light ( Volvo went their own way on DTC codes). I have been all through a '40 Farmall H (motor, transmission, hydraulics, etc.), various other tractors, combines, and assorted vegetable equipment. I can measure, cut, and fit to a few thousandths. I have a lathe, but have been using carbide tools since my tool grinding skills are still not 100%. My welding skills are so-so, but two neighbors are very good. I have calipers, mics, dial indicators, straightedges, a 12 T press, a decent set of hand tools, a 9000# lift in my garage...

Greg

Click to expand...

Ok, cool. A simple fixture can be whipped up to hold the bike. A base plate, perhaps 3/8" (minimum) to connect to, tacked to a BIG workbench, or lagged into the floor, will afford holding power. Picking up the iso holes, also grab the bottom horizontal tubes, using an angle iron or larger tube to be sure you don't mar/kink the tube. To grab the steering neck, a couple discs about the size of the bearings, minus .005" to allow a slip fit, with a stout bar ( 1" or 1-1/4") through. A big pipe for leverage will afford you the beans to yield the position of the headstock. Be patient, increase force gradually until some change is observed.

Click to expand...

When i did mine i did this... that 16mm plate is clamping the frame to the floor with masonary anchors... I positioned the frame/anchors in an appropriate place to take advantage of colum of garage.. Whilst its PITA, i forced/pulled on several occasions and refitting with levels (laser) and string lines to recheck how much i had reduced the miss-alignment of head tube to isolastic centres that are all working in conjunction of my "datum point"... 3rd time lucky and its now within a mm..

One thing that you omitted in your "skillset" was initiative and understanding the reality between "that as good as i can do and its better that the factory supplied" and "perfection".....

splatt said:

gjr said:

Hi Steve,

I am heartened by your success with getting things more or less in line and having the bike ride well. I'm going for somewhere between anal perfection and the hobot mash it into submission.

concours,

I am fairly handy at fixing things. I put the motor in this bike together about 50,000 miles ago and have just put in 0.020" oversize pistons a few years ago. Our local bike shop handled the machine work. I have several Volvos ('67, '87, '04) that I maintain. The '04 is demanding better diagnostic tools to sort out the ABS light ( Volvo went their own way on DTC codes). I have been all through a '40 Farmall H (motor, transmission, hydraulics, etc.), various other tractors, combines, and assorted vegetable equipment. I can measure, cut, and fit to a few thousandths. I have a lathe, but have been using carbide tools since my tool grinding skills are still not 100%. My welding skills are so-so, but two neighbors are very good. I have calipers, mics, dial indicators, straightedges, a 12 T press, a decent set of hand tools, a 9000# lift in my garage...

Greg

Click to expand...

No all totally inadequate, when you log in your name needs to come up in blue like all the other knowledgable Norton experts, most of there bikes run like a dream, because that's all they are

Click to expand...

Very funny I was getting that impression myself.