Gearbox Cradle

The cradle's two main plates that holds the gearbox/engine mounts in position via the iso mount............ are they to be symetrical to the center line of the front and rear axles ???????????????????? i ask this because the C/Line of the head is a few millimeters to the left taken up by the headsteady mount. The isolastic housing tube is "offset" to the cradle plates........... all these "offsets", eg front, rear iso's and head steady are becoming confusing to me.

I am trying to "predetermine" the PTFE washer/spacer requirements....

Keith1069 said:

As you've seen there is 3/16" appx more stickout of the tubes on RH than LH. So, the cradle and front mount are offset that much to the left of frame centreline. The confusion comes when getting the wheel back in line. Mine is built offset to the right to align with the front. You will also hear that the swingarm is built offset to the right and wheel centred in it. Of the (only) 3 I've ever worked on the swingarms were not offset but that didn't include MK3 which could be with its different hub set up etc.
Best thing is to measure swingarm front mounting pads to fork ends and see what you have. If it's not offset you can put a centreline on the swingarm pivot tube, mark for opposite offset and adjust rim to suit etc. That should align both wheels assuming the front is centred in forks of course. What you might find is that the cradle and front mount offsets differ. On mine the front was 060" out so the cradle was getting pulled/twisted to the left. So I let it find its natural position bolted up with zero iso clearance and with an empty crankcase fitted the front mount shimming it so it slipped into place with no force. That was after taking 060" off the right side and adding same to left side.

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Where's your frame centre line? Too many assumptions and you want to align the rear wheel with the frame centre line, when you've found it, after squaring swing arm pivot to steering head. Front gets aligned to steering head centre. See http://vintagenet.us/phantom/wsc.html. We've been here before - get your tape out olChris :lol:

Norton shifted the whole power unit, [engine to swing arm] off to the L to give tire chain clearance and the un molested 750's I've seen all had some rear tire offset to the L. The 750 swing arm is asymmetric with L leg straighter than the R leg which is spread out at an angle more before straightened up to be square to axle. The tire is centered at the front of swingarm spindle so can align tire-chain by just getting tire space equal there. Head steady also shifted to L by 3/16" or more to attach off set power unit to central spine line. You can relace rear rim to get tire in the middle so matches fender and tail light center placement. If ya didn't have funny handling prior its a cosmetic improvement more than anything else.

olChris said:

The cradle's two main plates that holds the gearbox/engine mounts in position via the iso mount............ are they to be symetrical to the center line of the front and rear axles ???????????????????? i ask this because the C/Line of the head is a few millimeters to the left taken up by the headsteady mount. The isolastic housing tube is "offset" to the cradle plates........... all these "offsets", eg front, rear iso's and head steady are becoming confusing to me.

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http://www.nortonownersclub.org/support ... el-offsets

Commando wheel offset - the definitive answer

I have the definitive answer as to what is offset, how much, and which way!

I set up a 1973 850 on the frame table and verified it was straight. I then put together a dummy engine and installed it with new isolastics, new washers, Hemmings adjusters, and a Norvil head steady. I put both adjusters on the left side, checked the swinging arm in my fixture and then installed it in the frame. I took all the play out of the adjusters and started measuring:-

The frame is symmetrical
The engine/gearbox cradle is offset 1/8" to the left.
The swinging arm is offset 1/8" to the right so the axle pads end up centred in the frame

I then installed the rear wheel:-

The spoke flanges are offset 1/8" to the left as mounted in the arm, so the rim is laced off 1/8" to the right to put the tyre in the centre
The centre of the rim is 3.3/8" from a straight edge laid across the brake drum (not the backing plate

With the stock Dunlop rim, if you sight across the rim on the brake drum side you will see about 1/16" of hub when it's in the right place. In my opinion, front and rear adjusters should be on the same side. Otherwise as things wear and you take up the slop you angle the engine and gearbox in the frame. Since the swinging arm mounts to the cradle, a little one way in the front and a bit the other way in the back and the rear wheel is out of line considerably. The chain will still line up but the wheels will not.

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olChris said:

I am trying to "predetermine" the PTFE washer/spacer requirements....

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Why not shim your isolastics the way that the factory service manual recommends? You can find this in Section F4 Paragraph 3:
"...(the shims should be divided equally between left and right)... "

L.A.B. said:

http://www.nortonownersclub.org/support/technical-support-commando/wheel-offsets

Commando wheel offset - the definitive answer

I have the definitive answer as to what is offset, how much, and which way!

I set up a 1973 850 on the frame table and verified it was straight. I then put together a dummy engine and installed it with new isolastics, new washers, Hemmings adjusters, and a Norvil head steady. I put both adjusters on the left side, checked the swinging arm in my fixture and then installed it in the frame. I took all the play out of the adjusters and started measuring:-

The frame is symmetrical
The engine/gearbox cradle is offset 1/8" to the left.
The swinging arm is offset 1/8" to the right so the axle pads end up centred in the frame

I then installed the rear wheel:-

The spoke flanges are offset 1/8" to the left as mounted in the arm, so the rim is laced off 1/8" to the right to put the tyre in the centre
The centre of the rim is 3.3/8" from a straight edge laid across the brake drum (not the backing plate

With the stock Dunlop rim, if you sight across the rim on the brake drum side you will see about 1/16" of hub when it's in the right place. In my opinion, front and rear adjusters should be on the same side. Otherwise as things wear and you take up the slop you angle the engine and gearbox in the frame. Since the swinging arm mounts to the cradle, a little one way in the front and a bit the other way in the back and the rear wheel is out of line considerably. The chain will still line up but the wheels will not.

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The definitive answer! No small claim. The author is not taking into consideration that every frame will be different due to variables in manufacture.

Al-otment said:

The definitive answer! No small claim. The author is not taking into consideration that every frame will be different due to variables in manufacture.

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Well, perhaps definitive enough to satisfy the majority of Commando owners who may not be overly concerned about manufacturing variables to such a fine degree.

.

"The frame is symmetrical
The engine/gearbox cradle is offset 1/8" to the left.
The swinging arm is offset 1/8" to the right so the axle pads end up centred in the frame "

Perfect, thanks LAB,

"
Why not shim your isolastics the way that the factory service manual recommends? You can find this in Section F4 Paragraph 3:
"...(the shims should be divided equally between left and right)... "

You are right PeterJoe, i am overthinking it, as i have adjustable iso's that came in my basket with no cups and PTFE washers to be found..

L.A.B. said:

Al-otment said:

The definitive answer! No small claim. The author is not taking into consideration that every frame will be different due to variables in manufacture.

Click to expand...

Well, perhaps definitive enough to satisfy the majority of Commando owners who may not be overly concerned about manufacturing variables to such a fine degree.

Click to expand...

Or handling.

olChris said:

.

"The frame is symmetrical
The engine/gearbox cradle is offset 1/8" to the left.
The swinging arm is offset 1/8" to the right so the axle pads end up centred in the frame "

Perfect, thanks LAB,

"
Why not shim your isolastics the way that the factory service manual recommends? You can find this in Section F4 Paragraph 3:
"...(the shims should be divided equally between left and right)... "

You are right PeterJoe, i am overthinking it, as i have adjustable iso's that came in my basket with no cups and PTFE washers to be found..

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Don't forget Keith1069 posted (and then removed it?) that the offset is 3/16" of an inch - that's 1/16" difference between "the definitive" offset. How do you know who is correct?

Don't forget Keith1069 posted (and then removed it?) that the offset is 3/16" of an inch - that's 1/16" difference between "the definitive" offset. How do you know who is correct?

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That's why I said 'appx'. and the front mount was different to the cradle. A quick way to determine what Norton originally intended is to measure the head steady. Both the pressed 750 and fabbed 850 styles come out at 3/16" (of the 3 or 4 I've measured. I removed the comment al-otment because I didn't spell out the full story. You were correct on that. Everything has to be measured of course but If its just about setting up shimming we've all gone off the thread and the original poster was confused anyway.........TMI :?

Keith, thanks for your reply.. With it and others i can/have determined that the two main plates of the cradle and the front iso are a "cuppla mm" to the left of front and rear wheel centerlines.. I have adjusted the iso shimming to suit but now awaiting for my wheels to arrive this week.....

Ok Chris no problem. Glad you got what you needed. Didn't realise you were trying to even up the shimming side to side...is that what you were aiming to do? Anyway hope it rides OK.

Al-otment said:

L.A.B. said:

Al-otment said:

The definitive answer! No small claim. The author is not taking into consideration that every frame will be different due to variables in manufacture.

Click to expand...

Well, perhaps definitive enough to satisfy the majority of Commando owners who may not be overly concerned about manufacturing variables to such a fine degree.

Click to expand...

Or handling.

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So, how far out of alignment can a Commando be, due to manufacturing variables, before it becomes noticeable or begins to affect handling?

Al-otment said:

Don't forget Keith1069 posted (and then removed it?) that the offset is 3/16" of an inch - that's 1/16" difference between "the definitive" offset. How do you know who is correct?

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The Commando head steady has 1/8" built-in offset, therefore, presumably, 1/8" is the definitive offset (although the cradle is probably nearer 3/16") and the head steady can be rotated, or the mounts shimmed to suit.

mk3-head-steady-offset-holes-t15446.html

L.A.B. said:

So, how far out of alignment can a Commando be, due to manufacturing variables, before it becomes noticeable or begins to affect handling?

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I don't know. What I do know is if the swing arm spindle axis is not square in two planes to the steering head axis then you will have problems due to the rear wheel centre line moving to and fro from the frame centre line plane as the swing arm moves when the rear suspension absorbs bumps. This is especially noticeable on Commando's because of the side clearance in the isolastic design. The iso's are not the problem though - it's the frame geometry.

When I aligned my frame I got the swing arm and steering head axes as close as I could to square i.e less than 0.001" away from parallel to the datum. Excuse the mixing of units (degrees and inches). The way I do it means there is no extra effort working to this tolerance. Without using a calibrated fixed datum I don't know how anybody can accurately (+/- 0.0005") establish where the frame centre line is and that it is perpendicular to the swing arm axis.

Yoose guys are guessing and speculating on what maters to C'do handling and it ain't got hardly ANYthing to do with the 1/8 to 3/8" LH offset variations I've ridden to test for just this effect. To help balance the CoG of L offset power unit it helps to have rear offset to L hand some so Norton wasn't completely stupid delivering them with un-centered rear tire. I would bet anyone here that they could not detect 1/2" rear off set and 2" lean of rear out of vertical - until they worked up balls to break free in public to feel which side a C'do falls over to faster-easier by a few 10'th a second difference. Don't let your limited experience and concepts slap your brain to your butts, by claiming I'm calming its not good to have tires in line, but its a rather minor issue beyond anything 99.99% of street riding would detect. Front mount and cradle spindle are offset to LH and front mount needs 1/4+" trimmed off for symmetrical adj iso units. The R leg of swing arm is bent outward some before angled back straight for axle. Its the isolastic gaps and rubber cushions compliance with swing arm pivot in cradle taking up slack till frame twists rebounds to slap forks silly that upsets C'do's not alignment. I do state that its a waste of time to shoot for anything but nice assembly alignments and mainly pay attention to the chain alignments that really matters most and leave ya to banntering on this and that mystery of what to waste time and money on for the most fun and smoothness. Top link only helps vertical plane tipping, front link only helps front gaps from slapping, its the rump link that's got the leverage to stifle THE Hinge onset. To get motorcycles not to climb road crown hands off move mass to the other side, either by removing LH items or shifting rear to L some more.

Al-otment said:

L.A.B. said:

So, how far out of alignment can a Commando be, due to manufacturing variables, before it becomes noticeable or begins to affect handling?

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I don't know. What I do know is if the swing arm spindle axis is not square in two planes to the steering head axis then you will have problems due to the rear wheel centre line moving to and fro from the frame centre line plane as the swing arm moves when the rear suspension absorbs bumps.

This is especially noticeable on Commando's because of the side clearance in the isolastic design. The iso's are not the problem though - it's the frame geometry.

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I think for you to say "you will have problems" is just speculation? I don't know if my Commando's swinging arm is exactly perpendicular to the frame or not, I somehow doubt that it is, but I haven't experienced any problems as such.

Al-otment said:

When I aligned my frame I got the swing arm and steering head axes as close as I could to square i.e less than 0.001" away from parallel to the datum. Excuse the mixing of units (degrees and inches). The way I do it means there is no extra effort working to this tolerance. Without using a calibrated fixed datum I don't know how anybody can accurately (+/- 0.0005") establish where the frame centre line is and that it is perpendicular to the swing arm axis.

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What was the actual outcome? Did you or, preferably, an impartial third party notice any improvement in the handling or ride afterwards?

ludwig said:

L.A.B. said:

So, how far out of alignment can a Commando be, due to manufacturing variables, before it becomes noticeable or begins to affect handling? ..

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I believe that depends on how you ride ( if at all ..) and what your expectations are .
So for the vast majority here it is of no significance at all if their bike is misaligned .

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+1

If you were to clamp a laser pointer to end side of the swing arm and a target plate each side of the front down tubes then went for a spirited ride (maybe even moderate) I am fairly sure on left to right transitions the results would be eye opening. (even sweeping corners at tip in)
It would make a mockery of a cradle and components set up to the imaginary 0.001"

Realistically, besides chain alignment wear and lack of ease to assemble the more out of spec a C'do is the sooner/faster it starts fork wobble onset *when**hands off** is main thing I have noticed, on top of state of tires inducting it more. This occurs on me [only un-tamed c'do] anywhere from slow idle pace to upper 50's mph. Next thing that shows up in out of line C'do is more vibration and later or no isolation as iso gaps bind unless opened up which shoots handling in the patches. Extra credit given by me if ya can describe or have experienced difference between head steady binding vs front or rear iso contacting. Some miss alignments cause continous vibration others only in cyclic intervals. If forced into THE Hinge onset by going too fast/powered/leaned in windy lumpy long sweeper conditions I find THE Hinge is easier/sooner/wilder when induced by LH turns than RH , yet on the other hand I can wind Peel's frame up about an inch out pegs to stem, so a bit better launching into R hander than L, yet its the opposite sense if *both* tires kept in *decent* traction, ie: a sosh easier to tip-aim into LH'rs than RH's. Best wishes surviving what it takes to develop this sense of how little offset CoG and tires in line matter. For any one that cares, like me, if ya can get crossed up a bit so tires patches spread a few inches wider the bike gets a lot more stable than balancing in same line, exactly like standing on one foot or putting another down a foot apart. Conflicting physics to over come, too stable is a drag while not stable enough, 1st is alright, 2nd gear hang on tight, 3rd gear out of sight, 4th gear
Dearly Beloved we are gathered here...

Time Warp said:

It would make a mockery of a cradle and components set up to the imaginary 0.001"

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I'll agree with that one. Splitting hairs?

Dave