Gearbox crack

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Nice work but I didnt see the crack between the bores.
I guess you spun the bearing without cracking it.
As for a stronger shaft, Id be interested but aside
from some sort of high grade steel what can
you really do without a lot of changes?
 
I'll have to post generally in hopes of the source of the better main shaft.
I cryogenic tempered then tungsten dioxide dry friction coat guts
to help take wheel lifting loads i crave.
But only bullet proof solution is $3500-4500 TT super duty version.
http://www.ttindustries.com/comparison.html

hobot
 
hobot said:
to help take wheel lifting loads i crave.

hobot
Click to expand...

I feel for you. That's how I blew mine up.
My Superduke doesn't have that problem :twisted:

Will
 
The crack is there but barely visible. Crack in itself is not a problem, it's the loose bearing. Box kept jumping out of gear, checked the sprocket, moved axially, and you know enough. Tried it twice with loctite, second time also roughing up the bearing surface in a silly way, you will agree... The whole job was just an experiment, a just-give-it-a-go, or call it pre-pensioner training, and the casing was otherwise lost anyway. The only thing that counts for the bearing is that is stays fixed where it is, axially as well as radially. I figured the forces on the bearing are limited (leaving possible flexing aside of course). Had seen some examples on japanese bikes, nothing special really. Sometimes it are litle fixing plates, or even circlips, or if space is limited with the help of a circumferential groove in the bearing. Problem with the AMC box is that there is not much room or meat (wall thickness). I am an amateur, the only machining I ever did was briefly at school almost 40 years ago. Came across this Emco lathe with milling head. Is fun to do some catching up.
 
Keith1069 might have a point there because the early AMC type shells look like they're die cast and the later ones look like they're sandcast.
 
Slim, you nothing to lose experiments are not wasted on me.
It confirms that there has never been a success in Commandos
using loctite to stablize a bearing in its bore.
So will have to figure out a way to mechanically pin it down,
hopefully less complex than your display.

There are some special epoxies that might work to fill in
then bore out, will be investigating that as old fart experiment.

Will, Ducati's of any type are like bait fish or flashy lures to Ms Peel.
Ain't much strain on her gearbox to tackle them if there are corners
of any sort that requires some leaning under power. They are
great straight line sprinters though, so eventually expect I'll
need the $4000 TT Industries gear box to haul em in on the
freeway like opens. 3rd gear is the weak link to drag race
the big moderns I found out.
Personally detest the valve clatter
and piston hit vibes transmitted in non rubber baby buggies.

hobot
 
hobot said:
Willll, Ducati's of any type are like bait fish or flashy lures to Ms Peel.
Ain't much strain on her gearbox to tackle them if there are corners
of any sort that requires some leaning under power. They are
great straight line sprinters though, so eventually expect I'll
need the $4000 TT Industries gear box to haul em in on the
freeway like opens. 3rd gear is the weak link to drag race
the big moderns I found out.
Personally detest the valve clatter
and piston hit vibes transmitted in non rubber baby buggies.

hobot
Click to expand...

Sorry if I mislead you somehow, I was referring to my modified KTM 990 Superduke. This bike Loves corners and power wheelies. Standard style bike with nice thrust, wicked feedback, and control to fill all my hooligan needs.

I get you on the vibes thing though, we all have different tolerances, I personally dislike some single vibes, rigid H-D Sportster driven in anger has a real bad effect on my senses, inline four buzz does a number on my wrist - hands, but no problem with 90 degree twins and my present 75 degree is very tolerable.

The Norton tranny , while slick shifting, is a real weak link for enjoying the big Norton torque.

Will
 
Hi there , an "Bravo" to slimslowslider !!! you are in Ludwig league......that's clever, and surely will work.
 
The cracks that first form in engine to gear box cases are so fine
they are right at limit of unaided human vision to resolve.
They don't usually start at the visible surface either.
Got to see a welder exploring stress risers in my cases by
melting away and away ugh and away some more, to find and
fix the finest curly cobweb spider silk dark line against the bright Al melt
I could imagine. W/o it pointed out to me I would have missed it.

For about 30 min or so I can actually enjoy the clattering of
any sort of bike, but after that its annoying to damaging.
My modern bike is 'curry' '00 SV650, upgraded suspension.
Its seems pretty pleasant until 20-30 miles then it feels
what it is, a mere road appliance economy ride.

Under powered Supermotards that can barely hit 80-90 tops,
out here do beat the sports bikes in their groups into town by
a hand full of minutes over 20-30 mile stretches.

I'll try to preserve my over powered Ms Peel AMC gear box
by pilot control and never intend to press my factory
Combat in clutch dump sprints, but figure a $4000 TT
tranny installed before I can let Peel's hair out. Fortunately
it don't take much power to womp other bikes
on a rump rod Commando, don't have to hardly
slow for corners and can stay on nice power though
turns, so not too hard on transmission holding back that much.

hobot
 
That's quite a clever solution. As you pointed out, the problem is the loose bearing fit, not the crack. I'll keep your method in mind if I ever feel the urge to repair any of the stock shells I have, all of which have cracks and loose bearing bores. I had considered some that would take much more involved machining operations, but yours looks much more practical.

One of Kenny Dreer's solutions to gearbox problems was to fit a Baker HD Big Twin gearbox. I don't recall if he used the 5-speed or the 6-speed. Bulletproof, but a bit expensive, and not easily fitted to a Commando. Besides, wouldn't you have to call it something like a Hardley Nortonson?

Ken
 
Hmm, if I think this is tricky maching and Ken thinks its straightforward,
ugh, thinking out of the box hay seed style,
I'm thinking of soldering my worn bores by 'low' temp alloys.
Last I got was 158'F to fill small tubes for kinkless sharp bends.
But vendor has a range of fairly specific melt point alloys.
Some melt at the temp was use to remove-install bearings.

Place bearing then flow in the alloy like watery wax, careful
not to get in bearing. To remove heat and tap out as usual
but on paper to recover the alloy splatter. Texture bearing
race and bore for mechanical lock up, not mere adhesion.
So what down side or caution am I missing??

hobot
 
lcrken said:
That's quite a clever solution. As you pointed out, the problem is the loose bearing fit, not the crack. I'll keep your method in mind if I ever feel the urge to repair any of the stock shells I have, all of which have cracks and loose bearing bores. I had considered some that would take much more involved machining operations, but yours looks much more practical.

One of Kenny Dreer's solutions to gearbox problems was to fit a Baker HD Big Twin gearbox. I don't recall if he used the 5-speed or the 6-speed. Bulletproof, but a bit expensive, and not easily fitted to a Commando. Besides, wouldn't you have to call it something like a Hardley Nortonson?

Ken
Click to expand...

Why wouldn't you repair the gearbox bearing from moving like you did the crankcase bearing? Seems way simpler?

Gearbox crack


short-stroke-750-build-t5490.html
 
Yes simple pin in place was what I had in mind prior to alloy melt.
Its seems so straight forward there must be a reason its not
been mentioned here by seasoned Nortoneers.
So what not a set screw or two in AMC box?

hobot
 
hobot said:
Under powered Supermotards that can barely hit 80-90 tops,
out here do beat the sports bikes in their groups into town by
a hand full of minutes over 20-30 mile stretches.
Click to expand...

My 640 supermoto pushing 60hp ruled the local tight twistys and was capable of 110mph, but sadly any highway distance made the vibration extremely fatiguing. Kind of like my Commando with the Isos set near zero clearance.

I also thought about putting a RZ 350 gearbox,( because I have one), or H-D Sportster box into the Commando but my interest in that project has declined.

My P11 will be running D-S tires so less grip to be binding up the gears. I expect that the Commando box should be fine for the intended use,( dirt roads).

Will
 
Yeeehaw Will, 60 hp on light bike and handy pilot is tough act to follow.
I like a good factory Commando on loose stuff better than made for
it dirt bikes.

Weird thing I noticed in un-tamed-un-rump rod Commandos on
loose stuff-THE Gravel,
seems to skip tires side to side to pivot at pilot seat level rather
than planted tires and bike tipping on contact patch as pivot.
With rump rod, settled down to act like expected and then
beyond expectations.

Most critical thing on THE Grit, is lower air pressure, softest
compound and slick tire, and never ever brake with front
tire turned any at all or SPLAT before you know you goofed.
If you can dig tire into surface, like pavement or hard pack
with loose layer on top, tire grooves have no effect but
less contact and more tire squirm.

If you can ride loose and predicable on THE G, then pavement
is childs play, mainly because if you let off on tarmac you get
some results to inputs, but once rolling on stones, you are
on lubed rollers so only pure ballistics and tire spin mass ejection
jets havr any hope of controlling what part goes down first.
You can't load a tranny to break one on THE Gravel, so no worry mates.

hobot
 
swooshdave said:
Why wouldn't you repair the gearbox bearing from moving like you did the crankcase bearing? Seems way simpler?
Click to expand...

Actually, I probably would do it similar to the crankcase. I guess I could have been clearer. What I meant was that I had never thought of pinning the bearing, because I was focused on fixing the crack. I didn't mean that I would do it exactly the same way, just that I liked the approach of fixing the real problem, i.e. bearing rotation, instead of worrying about the crack. Given that I've been doing main bearings that way for years, it's a little embarassing that it never occured to me to do the same with the gearbox. New ideas for old problems is just one of the reasons I appreciate this forum.

In fact, I think I might look at pinning the bearing right from the start, as a preventative measure. Maybe it wouldn't wear the bore in the case so rapidly if it couldn't rotate.

Ken
 
Hello swooshdave, yes sure looks way simpler. Looks like bearing is not recessed, bearing is protruding just a few tenth of a milimeter from the casing so washer will clamp on it with some force, I guess, and this force should prevent outer ring from turning. So washer is sticking out from casing, no problem as there quite a bit of "air" between crank web and casing. This air is not there at the sleeve gear bearing in the gearbox however, anyting that goes in there should not protrude over the bearing or the sleeve gear will touch it. I had no means to properly mill the bearing to suit a round washer.
Actually, thanks for the tip, had not seen it before, I might use it on my A65 BSA, it has the conversion to needle/ball bearing and, you guessed it, it is sitting loose...
 
Hobit
You like a commando in the gravel try a P11
Click to expand...

This gearbox and drive train weakness in general has cost me a bunch.
Almost the equivalent of a TT Industries gear box. Do ya know if
you smack a bearing hard enough to try to get it to stay in an
over worn bore - can pop it right out thought the case. Very
satisfying definitive end to dealing with that particular case.

possm, You Have Touched TWO Raw Exposed Nerves of mine,
P!! and THE Gravel.

P!! P!! P!! P!! P!! P!! P!! P!! P!! P!! P!! P!! P!! P!! P!!!!!!!!>>>
My 1st bike was a dedicated dragster age 20, got cheap because
dropped at strip and running on one jug and 18 yr old kid
who inherited it knew nothing about it and had a Kiwi 750 two stroke.
A English 10 spd bicycle towered over it leaning on a wall.
I got it started in my nerd penny loafers and slide rule holster
on polyesther pants. Thumpered around tight residential turns
awed by the strong torque at less than half power, when
came upon short straight steep down hill street ending
in row of houses. About 3/4 throttle a sec or so I cried
UNCLE as the acceleration when coil dried out and BANG
straight vertical wheelie, feet flew off pegs, I hung off
bars which gave it All of Full Throttle as flimsy seat front
broke free to slap me in face - flailing like flag at insane
G pull. More to story but I died and was resurrected that
day and never been same since. Oh yeah It'd flat leave
those 750 2 smokes behind over 100 mph.

P!! main down fall was it had no lean clearance, only
rear spin steering in town and it vibed hands to tooth roots.
A P11 rider, Tom Davenport of Phantom Oiler reference site
sent me to Bob Patton and his isolastic rod solution, I've
never been the same since on same scale sideways as
that P11 leaping forward G's. Its gearbox took it all fine.

THE Grit THE G THE G THE G THE G THE G THE G THE Gravel
I have unique water ski path, miles best groomed crowned hard
base loose layered marbles and arrow heads roller coaster
Newtonian to Quantum physics Demonic teacher around.
I have learned to ride tarmac as loose as THE Gravel,
but its only fun on my rump rod'd wonder, deadly scary on
anything else.

My dream machine will be quicker-faster than P!! dragster
and handle better than supermotards and cruise more easy comfy
than a big ole Goldwing yet sound-look like a real motorcycle.

hobot - Norton twin imprinted to the marrow.
 
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