improved gear box cradle design

Hello to all. I recently finished up a gear box overhaul on a 750 SS. Could not get the gearbox free and had to rebuild it in place. I now have a spare gear box cradle on my bench and am deciding if I should have one made with better cut outs, welds, lighter weight, Kegler clamps, etc. Would there be a market for such an improved cradle? A few folks in my area have said that most cradles have sufficient cut outs for gear box removal. I would like some of your learned opinions.
Thanks
Mike Gallagher
Norton Colorado

mikie3117 said:

Hello to all. I recently finished up a gear box overhaul on a 750 SS. Could not get the gearbox free and had to rebuild it in place. I now have a spare gear box cradle on my bench and am deciding if I should have one made with better cut outs, welds, lighter weight, Kegler clamps, etc. Would there be a market for such an improved cradle? A few folks in my area have said that most cradles have sufficient cut outs for gear box removal. I would like some of your learned opinions.
Thanks
Mike Gallagher
Norton Colorado

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Aluminum would be cool. See the stuff that ludwig and hobot have done. Very cool stuff.

Wonders never stop on variation of Commando mis fits. Besides your listed features consider the reports of 850's fractures at cradle holes so beefing them up not a bad idea. As so simple to open up steel cut outs and pretty darn rare to trap a tranny, can't see much market for em in that material. This is one way to do Al cradle. I'd guess this level would have to sell for around $5-600 without much mark up for what i'd take to produce. 6601 T6 5/16" plate.




I added the tang for rump rod mount and cross brace at rear to stiffen for link loads. The spindle lock bolts are vertical aligned, allen wrench access from top. The spindle is almost interference fit in the cradle path. Its toss-able catch-able by one hand and distinctly felt as less a Commando under there.

I've heard some modify the original so the GB will come out without moving the motor. That would be an improvement. Like to see the drawings. Probably only take timing side mod?

Dave
69S

I had initially borrowed an industrial grinder and started to remove enough metal to get the box out but gave up. Lots of smoke, vibration, noise and little progress!
We made some a pretty cool drivers for the bearings, borrowed an inside puller and heated the heck out the case for reassembly.
I was spoiled having done a few gearboxes on my bench with Fred Eaton's notes at the ready.
I have considered aluminum and like what Hobot did. There seems to be lots of room for improvement over a stock cradle.

Mike

I suggest you need to know if you have a NA box (Commando) or N Box (Atlas). The later NA box has a 1/8" narrower top bolt bolt boss to allow easier removal of the box in relation to the 15 degree tilt on the Commando motor. Also consider the factory had 7 years of experience with this assembly and knew what limitations could be imposed on the load bearing points. Any improvement would have been recommended by the NVT dealers who recommended many practical improvements subsequently shown in Service Bulletins. My opinion is that what we have on the NA box cradle is about as minimal as it can get, taking any more out of it is likely to shift stress paths somewhere with unhappy consequences.

Mick

Colorado Norton offers a carving out service for cradle for removal of gearbox without disturbing
engine. I have a TTI box that requires some relieving. Without machine tools it is no walk in the park!
I have not yet run the bike so unkown as to cracking problems but I admit I worry.
Asked Matt at CN about alloy cradle, said no they dont and wont offer as to be as strong it gets too
big and doesnt save much weight. Think that RGM offered one in the past maybe they run it up to
your order, likely in the off season.
As I rebuild my Norton Ive come to realilze that at some point there is precious little Norton
left if you go for all the mods. That is all fun and games for the cafe types but if you want to
know what a Commando is, or was, actually like it is going down the wrong road.
Where does one draw the line?

ML said:

I suggest you need to know if you have a NA box (Commando) or N Box (Atlas). The later NA box has a 1/8" narrower top bolt bolt boss to allow easier removal of the box in relation to the 15 degree tilt on the Commando motor. Also consider the factory had 7 years of experience with this assembly and knew what limitations could be imposed on the load bearing points. Any improvement would have been recommended by the NVT dealers who recommended many practical improvements subsequently shown in Service Bulletins. My opinion is that what we have on the NA box cradle is about as minimal as it can get, taking any more out of it is likely to shift stress paths somewhere with unhappy consequences.

Mick

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From my research over the last 20+ years ...An 'N' box is early atlas (like my 63) with the long kick start bush among other items, the "NA" is late atlas (like my 66&68) and I have NEVER seen one in an original/unbutcherd 68-75 commando. Both of these boxes are rather thin cases and though they will bolt into a commando are rather unsuitable IMO.

The cradle upgrade being proposed for gearbox removal is (IIRC) standard in the MKIII and would seem to be a worth while mod when you have the cradle out rather than wait for an emergency and then complain because you don't really want to jocky the engine to pull the whole box out.

NA makes the new cradles with taper pin style mounts I wouldn't be surprised if NA & ZFD now make the opening in the replacement cradles to remove the gearbox.

Onder said:

Think that RGM offered one in the past maybe they run it up to your order, likely in the off season.

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http://rgmmotors.co.uk/main.htm

066972A ALLOY GEARBOX CRADLES. CNC MILLED FROM TOOL ROOM GRADE ALLOY, STRENGRHENED COTTER PIN TYPE.
£ 390.00

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The tranny Commando or Atlas ain't the issue as the only fitting difference is the Cdo has the obnoxious notch and thick washer to fart with while the [later]Atlas don't thank goodness. Someone said the cable entry was different but I did not find any thing different in fitting Altas shell in my Combat but less hassle getting it in and out. It tips with same ease in cradle once the mount bolts freed. In Combats the low rear breather baffle prevent tipping shell forward to clear opening until engine tipped out the way 1st. One of the main benefits to me on the various aftermarket breathers is getting rid of the Combat fouling oil baffle down there. On my factory Trixie I was at first put off having to release engine but found it was more tedium than brute swearing and forcing straining.

I found out where the shells are the thinnest the hard way, knocking the mainshaft bearing right out through the end of the case, ugh.

To get my Qualfe box to stick out on DS enough I've had to grind both the Al cradle and some of the shell, so likely similar with the ITT box. Peel's alloy cradle has been though hell with drive chain jumping tract to run on very outside of teeth which jerked shafts bent and crushed bushes- then later with mysteriously powerful engine combo & lots of wild flings on & off road but held up fine and ready to go at it even harder someday.

The weak spots in cradles are the thin surround of the 3 engine bolts, especially the lowest one, not the over built side panels. I can't understand how the gear box got installed the first time if it can't be removed now, once anything fouling the shell shifting is dealt with. Its such a rare report, 1st I've ever read of, I can't imagine it worth while to gear up to make more than one in a row. Radical modifiers would shoot for alloy while traditionalist just stick with what they got. I got Peel's Al cradle from a racers left overs, not my design or creativity like ludwig or Brent Wolf and others.

Oh boy. Over joyed at hearing the lower forward engine mtg hole is
weak. I had to carve a bit out there.

I have built 2 sets of alloy front mount and trans cradles. here are some pictures of the second set. I incorporated the transmission opening relief to be able to remove it with engine in place, works well. I have also done this on my combat cradle with a die grinder and a carbide burr, went easily.






and the controversial swing arm of death.

DogT said:

I've heard some modify the original so the GB will come out without moving the motor. That would be an improvement. Like to see the drawings.

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Well this one was modified by the engine but the GB did not come out. Note the elongated upper rear engine mount - the metal pulled like taffy. This was the result of a race weary cast iron flywheel that fragged.

I like the novelty of an aluminum engine/trans cradle. There are plenty of alloy engine plates out there (Converta, etc) that never have a problem with supporting the engine and trans. The challenge for a Commando ISO application is getting the stiffness to properly support the swing arm spindle and the stiffness to transfer those forces from the spindle through to the frame.

Some really nice looking fabrication work there bwolfie.