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commando featherbed

I am new to this club so apologies if this has been discussed before, I am thinking of putting an 850 engine in a 1960 featherbed wideline frame, what sort of money would get me an engine, I will strip it and work as necessary, I have read various bits on doing this and 1 seems to be re balancing the engine, any help and advice on this would be great, what are your general thoughts on doing this.i am not trying to do a triton with clip on's etc. I prefer to be sat up a bit. I have some forks with twin disc callipers that may be able to be used from the early 90s, more homework on this. I did think about doing a Les Archer type design but the frame work is beyond me. Thanks Neil

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Hi Neil

Good project. You need to decide if you want a solid mounted engine or with isolastics. I imagine the front would be OK but the rear with the swingarm would need a bit of thought. When I got my Atlas on the road as a poor apprentice in the seventies, I ended up dreaming of a vibe free bike. Commandos were way too pricey so I stuck a Honda 750 motor in it. Instant nirvana. Never stopped dreaming of a Commando though and got one eventually.

Here are a couple of pics of a beautiful Featherlastic 750 which may inspire you. Not sat up as you like but yoga lessons or some quality gym time would sort that out

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Hi Neil,

I know a chap who did this, he also had the crank balanced for a rigidly mounted engine but it still vibrated too much so he sold it. He only got £5000 for it which would make the value of the rebuilt engine + gearbox and the tidy rolling chassis about £2500 each. Others have had more success using isolastics or rubber mounts. Any Norton twin engine over 650cc rigidly mounted in a featherbed frame is going to vibrate some what and as such are far more suited to isolastic mounting IE Commando. A 650cc featherbed is a fine machine anyway.

Regards, Al.

Wow thats some bike there Neil. But is it only semi-lastic? Looks to have the normal featherbed arrangement for swinging arm and gearbox fitment, but not the front engine mounting??

 

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To be honest, I dont really see the point of taking a perfectly good featherbed, putting a bigger Atlas engine in, then hold it together with rubber bands. If the vibration is an issue, just get a Commando in the first place, and stop ****ing about...Its like moving to the countryside, then complaining about the smell of the pigs**t....

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And another thing: mounting a Commando engine upright like I did, the Norton script on the timing cover slopes upward. So you mount the engine inclined as per Commando (I forget the angle- is it 15 degrees?). that solves the look of the timing cover, only now the barrels are not parallel to the downtubes, cos the Slimline has a different headstock angle to the Commandos...

Rant over.

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Very interesting Peter, looks like Michael was right with the semi-lastic, solid mounted swing arm if that,s the same bike as in my pics. I believe this setup was considered for the Commando at one stage but think chain alignment and tension problems killed it. Bet that 850/88 went pretty well Michael. The different engine and frame angles look acceptable in the Featherlastic pics

I,m quite happy with the Commando these days, smooth, grunty and good handling, in fact I reckon the Commando is the real Featherbed but a silver 650SS was the first bike that made me stop and stare as a lad

wow that's a beauty. I have thought about the isolastics, I have a P11 1967 and a 1976 Mk 111 commando, and vibe free is the way to go. I used to do a lot of gym and yoga but body is complaining a lot with my enduro riding, your bike doesn't look as bad as some out there for arse up head down riding. thanks again

 

Michael, you stay stop ****ing about, yet you have done it or had one, are you an ex smoker, in my mind its nice to challenge yourself and do something different, I have a bonnie 750 unit I could put in, never mind I listen and learn from all. thanks for your input.

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Interesting lash-up. I would cut and shut the Commando plates and use Silentblock car bushes from a car suspension. Landrover parts spring to mind. Done it once, use stiff bushes to stop the chain pulling too much. The pictures show a bad top mount which will shear those small bolts. You want to lift the plate up higher so that the mounting goes through it. The chain guide gives me the shudders. What is it for? When the chain breaks and wraps round it I reckon at seventy MPH you should get across the Grand Canyon. The first Norton in space, eat your heart out Elon!

what is the tank used on your bike (it is your bike isn't it) please, is it a standard Dommie. 

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For the anti vibration setup used in the dying days at Meriden they used slientblocs from the Triumph 2000 car engine at the bottom of the engine. 

 

A V Triumph

 

 

Neil

not my bike, looks like the Katz one in Peter Whites post from the USA with possibly a custom or modded tank. Very nice shape. My Atlas special uses the original '65 slimline tank but I,ll fit a new base to try and get a bit more fuel capacity.

I,d adapt an entire Mk3 type isolastic cradle assembly including the swingarm into the Featherbed rather than the solid rear. Swingarm may need mods to length and shock mounts position. I designed a solid, frame mounted pivot for the swingarm on my Mk3 but stayed with the standard setup for simplicity. Very glad I did, effective and works well

Use your own Mk3 dimensions from front iso to rear axle as a rough guide to see if it,s feasible. An inch or so longer swingarm not a problem and would help weight distribution, I,ve extended mine an inch already on the Atlas. Norvil iso head steady would be good.

Commando engine assembly is offset 5mm to the left of centre by the way, noticible when looking from the front of the bike or changing carb needles. Had me puzzled when making my own custom swingarm until I read about it in Steve Wilsons excellent Norton book

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Having had my knuckles soundly rapped by Neil H, in my roundabout way I was defending the featherbed design- admittedly from a point of ignorance of never having the opportunity to ride a Commando. I do accept that the Proddie Racers in the hands of Mick Hemmings and the like are excellent handling bikes when well set up, as is evident from TTs etc.

I cant recall seeing a challenging Dommie v Commando Head to Head, but I’m sure it would make "interesting" reading!

To come back to my point, to me it makes no sense for the structural dynamics of the featherbed frame, from the brilliant headstock configuration, back to the swingarm, with its excellent resistance to twist and flex, to be somehow compromised by rubber interfering with the swingarm mount (and yes I know the silentbloc bushes are part rubber)

I fully endorse the idea of isolating the engine, and I’m intrigued by John’s Meriden setup above. With a frame-mounted swingarm and gearbox - to ensure final drive chain alignment- and an isolated engine driving by belt to accommodate the relative flexing motion between it and the gearbox, I think that is an excellent concept for development. Just needs rubber chaincases too I guess!

PS My bikes may have smoked a bit, but I never did-although I fancy a John Player right now;-)

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I’m pretty sure primary belt drive as currently used on bikes would not survive just engine rubber mounting. The late Triumph had whole engine and partial swing arm rubber mounted from the drawing shown.

    Featherbed v. Commando: having owned and ridden both extensively, they are different, but not hugely so, so it comes down to personal opinions in any comparison. To me, the vibration isolation is the key winning advantage for actual riding experience.

 

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