ISO-cradle-frame alignment

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Cheesy

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I am almost at the stage of mocking up my frame and setting up the ISOs etc
Now the ISOs I have are an adjustable type where the fixed end cap is approximately 5mm shorter than the adjustable end cap, both of the ISO tubes are centred in their respective plates (ie the tube sticks out the same on each end), there were also some very thick low friction washers to take up the required space (when the adjuster is done up tight there is approximately 5mm gap total.

So far from what I have dug up the motor should be offset anywhere from 1/8 to 3/16 to the left of centre and obviously in line with the frame/wheels and the adjustable ISOs caps should be on different sides of the bike.

Since I have to do a bit of fixing anyway I may as well try and get it right..... So with that in mind how much engine to frame offset should I be aiming for and secondly are there any particular reason(s) for the orientation (left or right side of frame) of the adjustable ISO end?

Now when I get some numbers I am going to turn some aluminum caps/spacers (to replace the steel part that would have previously held the shims in place) to correct the alignment and make some washers out of a sheet of UHMWPE (yes I know it has a high thermal expansion but it is thin to start with and I will also have three links to help the transverse location so it will be possible to run them at a bigger clearance)

cheers Dave
 
Hi Dave,

Just curious, but why exactly should the adjustable iso end caps be on opposite sides of the bike?

My own, and every other Commando I have seen has them both on the same side, always the left side, at least on
my bike that side seems more logical, easier to get to.
 
1up3down said:
Hi Dave,

Just curious, but why exactly should the adjustable iso end caps be on opposite sides of the bike?

My own, and every other Commando I have seen has them both on the same side, always the left side, at least on
my bike that side seems more logical, easier to get to.
Click to expand...

To be honest I have no idea and I am questioning it but Im sure that I picked it up on here somewhere, could also be completely wrong on that one
 
1up3down said:
My own, and every other Commando I have seen has them both on the same side, always the left side, at least on
my bike that side seems more logical, easier to get to.
Click to expand...

Original Mk3 has the front adjuster on the right.
http://www.nortonmotors.de/ANIL/Norton% ... &Plate=015

Same for the Norvil vernier kit.

http://www.norvilmotorcycle.co.uk/techtalk04.htm
REAR
Fully screw the long abutment on the right hand side of the isolastic and tighten 2BA grub screw.
Fully screw the long adjuster to the left hand side of isolastic.
When the adjuster has been fully tightened, loosen by approximately half a turn. The unit is now set.
Fit the gaiters.
Fit the unit to the motorcycle and fully tighten through stud/nuts to 25FT/LBS (3.45M/KG).

FRONT
Fully screw the short abutment on left hand side of the isolastic and tighten 2BA grub screw.
Fully screw the short adjuster to the right hand side of isolastic.
When the adjuster has been fully tightened, loosen by approximately half a turn. The unit is now set.
Fit the gaiters.
Fit the unit to the motorcycle and fully tighten through bolt/nut to 25FT/LBS (3.45M/KG).
Click to expand...

http://www.norvilmotorcycle.co.uk/techtalk03.htm
The adjusting screw on the front unit must be fitted on the right hand side of the machine and the rear adjuster on the left hand side.
Click to expand...
 
L.A.B. said:
1up3down said:
My own, and every other Commando I have seen has them both on the same side, always the left side, at least on
my bike that side seems more logical, easier to get to.
Click to expand...

Original Mk3 has the front adjuster on the right.
http://www.nortonmotors.de/ANIL/Norton% ... &Plate=015

Same for the Norvil vernier kit.

http://www.norvilmotorcycle.co.uk/techtalk04.htm
REAR
Fully screw the long abutment on the right hand side of the isolastic and tighten 2BA grub screw.
Fully screw the long adjuster to the left hand side of isolastic.
When the adjuster has been fully tightened, loosen by approximately half a turn. The unit is now set.
Fit the gaiters.
Fit the unit to the motorcycle and fully tighten through stud/nuts to 25FT/LBS (3.45M/KG).

FRONT
Fully screw the short abutment on left hand side of the isolastic and tighten 2BA grub screw.
Fully screw the short adjuster to the right hand side of isolastic.
When the adjuster has been fully tightened, loosen by approximately half a turn. The unit is now set.
Fit the gaiters.
Fit the unit to the motorcycle and fully tighten through bolt/nut to 25FT/LBS (3.45M/KG).
Click to expand...

http://www.norvilmotorcycle.co.uk/techtalk03.htm
The adjusting screw on the front unit must be fitted on the right hand side of the machine and the rear adjuster on the left hand side.
Click to expand...
Click to expand...

Do you know the reason behind this?
 
We dont know if this is a hypothetical iso on a hypothetical bike . But hypothetically , if the fronts not spaced in relation to the rear fit , its hypothetically Wrong .

Say you set the Aft Arrangement , wack it down to ZERO clearance . Now , the front should be looked at as CENTRAL . Easier to explain exaggerating .

Say we have 1 / 2 in clearance aft . 1/4 in Ea Side .
With the whoo haa at the front set ' open ' we have a glare - Throw the rear fully right , measure gaps at front , Throw fully left . Ditto .

NOW , we do a few sums , and can fix front clearances equal ea side also .

Exaggerating again , say the front was set 3/4 in to the right ( or left ) off the rear . The Tubes for the rubbers would bind up the shimming in two spots opposite
EVERYWHERE . :oops:

SO , this is why squareness of mounts ( parrallel Iso Pins ) are essential . Set one end , and establish centrality of the other , for EVEN Clearances .

Theres a thing . :D
 
Ya can't get a probe on the adjusters if rear is not on the LH and the front on RH side I've found, after, ugh, reversing my initial install. The whole power unit is shifted to LH of center for the tire/chain clearance and more like 3/8" if ya go by center of rear wheel to spine and front tire. No Norton tires do not line up on same line just parallel lines 3/8" apart unless the rear hub respoked to change factor set up. Set gaps on bench they see how well or not they slip in the mount w/o engine involved then alter tabs usually the front &or grind the adjusters so they will slip in mostly w/o major force. I like to mount iso's on crade and engine case then place that as a unit into frame so only two bolts to align and slip in. While front rubbers easy to access I'd recommend beveling the front two big'in's by !45' to leave 1/4" flat rim to bare in tube on for sweeter sooner smoother Commando w/o any noticed handling issues not already innate in all un-tammed Cdo held on power thru rough sweepers approaching go to jail speeds. Adj as needed trail error later.
 
ludwig said:
My grasp of the English language is insufficient to understand what M. Spencer or Hobot are saying ...
Click to expand...

You are not alone!
 
hobot said:
The whole power unit is shifted to LH of center for the tire/chain clearance and more like 3/8" if ya go by center of rear wheel to spine and front tire.
Click to expand...

How can shifting the power unit to the left improve tyre & chain clearance? If the cradle is moved over to the left, the chain/wheel also moves to the left. It would be a different matter if the swinging arm was fixed to the frame.


hobot said:
No Norton tires do not line up on same line just parallel lines 3/8" apart unless the rear hub respoked to change factor set up.
Click to expand...


Correcting any apparent rim offset would have been easy, and to suggest the factory either didn't know or didn't care seems misguided.

As the cradle is offset, then both swingarm axle end plates and lower shock mounts would also be offset relative to the upper shock mounts, if so, then it would force both shocks to lean over to the right by 3/16"-3/8" which doesn't appear to be the case, so either the frame isn't symmetrical, the swinging arm isn't symmetrical or the cradle is not parallel to the frame (the offset tapering down to zero at the rear wheel axle) all of which appear to disprove any theory of the rear wheel being out of frame alignment because of the cradle offset.
 
Well, this is copied from NOC list notes from the above link.

Am I correct that at the bottom paragraph the conclusion is that the adjusters should be on the SAME side?





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.

Vernon Fueston on NOC-L 22nd. Nov 1997

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grandpaul said:
Because the factory manual says so, that's why.
Click to expand...

I have MkIII adjusters on front and rear and they are both on the LH side. I wonder if this is the end of the world?
 
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.
Click to expand...

For that to even be a minor concern, one would have to assume that the majority (or all) of the wear ocurred at the non-adjuster end of each Iso. which seems unlikely.
 
Thanks for all of the replies, it will be a few days before I can mock my frame up but at the moment I can say with certainty that the 750 swing arm is symmetrical and if I had my ISO adjusters on opposite sides there is no way that the bike would go straight.... also if I had the fixed ends on the LHS the engine assembly would be 3/16 to the left as the fixed end of the ISO adjuster is that much thinner than the adjustable end. I am starting to think that I have adjusters for whatever model had the ISO tubes offset, either way I can make them work with new caps
 
Cheesy said:
also if I had the fixed ends on the LHS the engine assembly would be 3/16 to the left
Click to expand...

The cradle would normally sit 3/16" to the left (of the frame centre line)?
ISO-cradle-frame alignment


Cheesy said:
fixed end of the ISO adjuster is that much thinner than the adjustable end
Click to expand...

[Edit:]I thought the rear Iso. fixed and adjustable abutment caps were more or less identical in width?
ISO-cradle-frame alignment



With the standard Mk3 front Iso it wouldn't be possible to fit the adjuster on the left side for the same reason.
ISO-cradle-frame alignment
 
ludwig said:
My grasp of the English language is insufficient to understand what M. Spencer or Hobot are saying ................
Click to expand...

i think that for even us with English as first language (or only) this applies too
 
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