one piece axle for mk3 commando

Status
Not open for further replies.

bobnorsaki

Joined
Jan 7, 2022
Messages
8
Country flag
the mk3 two piece axle is 17mm. If you cut the stud off the stud shaft and open it up to 17mm you can insert a one piece axle. I have used the axle from a 1983 kawasaki gpz 750. one must redeuce the length of the shaft and put threads on it for it to fit the swingarm.
 
bobnorsaki said:
the mk3 two piece axle is 17mm. If you cut the stud off the stud shaft and open it up to 17mm you can insert a one piece axle. I have used the axle from a 1983 kawasaki gpz 750. one must redeuce the length of the shaft and put threads on it for it to fit the swingarm.
Click to expand...
Hi,
im obviously missing something
What is the reason of changing to a one piece axle. Is there a significant problem with the two piece axle.
alan
 
Alan L said:
Hi,
im obviously missing something
What is the reason of changing to a one piece axle. Is there a significant problem with the two piece axle.
alan
Click to expand...

The main axle can snap in the area of the thread that screws into the dummy axle.
I can not say I have had a close look but that might be to under or over tightening or the axle (non threaded) shank not entering the dummy axle as support so the exposed thread fractures over time. (maybe)
In other words if the shank is down a bore it is supported a low stress riser (unlike a thread radially)

Edit.
Wire wheel Ducati's (750 GT's) of the same time period have a short carrier at the cush drive hub and a nut at the outer side of the swing arm which means the cush and drive chain stay fixed in place and the wheel can be removed as an option.
The difference is what would be the dummy axle on a Commando has a central bore so the one piece axle passes through it with another nut for the axle end.
 
Last edited:
I run a one-piece rear wheel spindle in a Commando race bike, been doing it since 1990. You do need to machine/file flats to fit the LH swinging arm eye (or open the eye up). I did it for stiffness in conjunction with some other mods for changing sprockets.
I've never seen or heard of the two-piece spindles failing so can't see why you'd do it on an otherwise standard road bike (unless you've lost the original parts).
 
I thought there were some documented breaks of rear axle , not positive , but when I ordered new wheels from Madass I also ordered the set of SS axles with the rear being one piece , I liked it as gave me new confidence
 
stanthomas said:
I've never seen or heard of the two-piece spindles failing so can't see why you'd do it on an otherwise standard road bike (unless you've lost the orioginal parts).
Click to expand...

It is a known problem and not just the 850 Mk3.

Another MK III broken axle (2018)

Pulled into my shop just as rear tire went flat. Thought what good fortune to have it happen right there. Repaired tube and, just snugging up rear axle, it snapped! Nothing new, classic fatigue crack - fine grain crack 2/3rds through until the final third broke. I remembered Hobot was counting...
www.accessnorton.com www.accessnorton.com
 
Craig said:
I thought there were some documented breaks of rear axle , not positive , but when I ordered new wheels from Madass I also ordered the set of SS axles with the rear being one piece , I liked it as gave me new confidence
Click to expand...
Were a couple posts deleted ? Thought I answered someone saying nothing wrong with rear axle ,…. or am I just old and mistaken …..
 
Craig said:
Were a couple posts deleted ? Thought I answered someone saying nothing wrong with rear axle ,…. or am I just old and mistaken …..
Click to expand...
I run a 75 and a 76 model MK 111 . Both axles/ spindles seem fine. Mind you I've always used plenty of grease on everything involved and only use snug up pressure on this topic , by feel. Feel is a learned thing after many years of mechanical stuff. 80 ft. Lbs. here is way too high. And that is why Chaz and I and others are re-writing the manual .
 
Time Warp said:
Wire wheel Ducati's (750 GT's) of the same time period have a short carrier at the cush drive hub and a nut at the outer side of the swing arm which means the cush and drive chain stay fixed in place and the wheel can be removed as an option.
The difference is what would be the dummy axle on a Commando has a central bore so the one piece axle passes through it with another nut for the axle end.
Click to expand...

Obviously this is sound engineering by Ducati. The solution chosen by Norton leaves a comparatively small cross-section in the threaded part of about 10 mm. Interestingly, the rear axle failure potential is not acknowledged by A-N.
Increasing the dummy axle from 17 to say 25 mm will require a larger dummy shaft bearing (double row ball bearing 4203 ATN9 -> 63005, OD = 47 mm) which will probably require a special rear wheel sprocket / carrier. In addition, the left side eye of the swinging arm needs to be machined for the larger dummy shaft (see #5). Yes, it looks doable.

- Knut
 
Last edited:
mdt-son said:
Obviously this is sound engineering by Ducati. The solution chosen by Norton leaves a comparatively small cross-section in the threaded part of about 10 mm. Interestingly, the rear axle failure potential is not acknowledged by A-N.
Increasing the dummy axle from 17 to say 25 mm will require a larger dummy shaft bearing (ball bearing 62203 -> 63005, OD = 47 mm) which will probably require a special rear wheel sprocket / carrier. In addition, the left side eye of the swinging arm needs to be machined for the larger dummy shaft (see #5). Yes, it looks doable.

- Knut
Click to expand...

This thread reminds to measure the outside width of the assembly in the bike so an idea (disassembled) of how that thread sits engaged in the dummy axle.
The sprocket carrier staying in the bike is handy at wheel removal.
Not the same but I did machine my DR650's sprocket cush drive carrier to take dual bearings (like a Ducati) instead of the stock one of.
The engine drives the fully supported carrier, the carrier drive the wheel but are then two fully independently supported parts.
Of course more bearings make for more possible failure parts in service.
(But I am no mechanical engineer)

Off topic on a slant.

one piece axle for mk3 commando one piece axle for mk3 commando
 
I find this interesting. I first became acquainted with this problem on Labor Day weekend (Autumn Bank Holiday equivalent) in 1971 when I was riding my 1970 Roadster. I began to be quite aware of this issue at the downhill right hander at the end of the back straight at Virginia International Raceway. I don't count the number of people who say "it's never been a problem for me"; I can assure you that I believe them because if it's happened to them, they would NOT have forgotten it.
 
I understand the designed-in weakness of the two piece rear axle - and maybe I'll change mine.
There is, however, a benefit (especially with cush-hubs) with the two-piece for road bikes. That is the rear wheel can be removed, to repair or replace a tyre, without disassembling the LH side - which can be a PIA to reassemble and squeeze back into place - especially pre-MkIII.
Are any one-piece owners willing to comment on the comparative ease/difficulty the one-piece axle presents in this scenario?
Cheers
 
mdt-son said:
Obviously this is sound engineering by Ducati. The solution chosen by Norton leaves a comparatively small cross-section in the threaded part of about 10 mm. Interestingly, the rear axle failure potential is not acknowledged by A-N.
Increasing the dummy axle from 17 to say 25 mm will require a larger dummy shaft bearing (ball bearing 62203 -> 63005, OD = 47 mm) which will probably require a special rear wheel sprocket / carrier. In addition, the left side eye of the swinging arm needs to be machined for the larger dummy shaft (see #5). Yes, it looks doable.

- Knut
Click to expand...
I think ZFD did.

Another MK III broken axle (2018)

Chaztuna and others (myself included) are updating the MK 111 workshop manual concerning helpful revisions and cleaning up a few omissions. I believe the 80 lbs./ft. in Section A causes potential problems. This might very well be changed to 50-60 and the word Axle placed after the word Spindle...
www.accessnorton.com www.accessnorton.com
 
robs ss said:
I understand the designed-in weakness of the two piece rear axle - and maybe I'll change mine.
There is, however, a benefit (especially with cush-hubs) with the two-piece for road bikes. That is the rear wheel can be removed, to repair or replace a tyre, without disassembling the LH side - which can be a PIA to reassemble and squeeze back into place - especially pre-MkIII.
Are any one-piece owners willing to comment on the comparative ease/difficulty the one-piece axle presents in this scenario?
Cheers
Click to expand...
You are spot-on. I have the 1 pc. axle
and wheel removal is more pain in the arse.
I bought the 1 pc. when I was going to include my then SO as pillion in a 150 mile group ride, based on failures discussed here.
 
Dunno about Mk3 but on earlier bikes you can turn the one piece axle around and pull it only partially out, so you still get the quick change feature. The chainguard holds the brake drum in place. Not difficult.
 
Status
Not open for further replies.
Back
Top