classic motorcycle forum
Motorcycle Discussions => British Bikes => Topic started by: Simon Ratcliff on October 04, 2016, 12:05:05 PM
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Hi, looking for advice/experience on a project I'm about to start.
The project is grafting on the front end suspension off a BMW K1200R Sport on to a 1970's Norton Commando frame. The reason is to take advantage of the superior design of front suspension and obviously ditch the telescopic Roadholders - I think telies should have been binned decades ago. The suspension is based on the Norman Hossacks design featuring two wishbones (lower and upper). The fork legs are basically a inverted solid U-tube shape, suspension is via a single shock mounted on the lower wishbone and a point on the frame.
Any advice appreciated.
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The Commando frame was designed to use conventional teles, and even Norton got it wrong with the early ones which suffered frame breakage near the steering head. I would have thought that the frame would need a complete redesign to use the telelever layout as you need a point to anchor the lower wishbone fulcrum that it obviously non-existent on the Norton.
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Ian, thanks for the comments.
Totally agree with your points regarding redesign of the frame, but only in the steering head area to support the lower and upper wishbone - it's the duo-lever design not the paralever. http://ridermagazine.com/wp-content/uploads/2005/09/2006_BMW_K1200R_front_wheel_Frame1.jpg
At the moment the idea is to remove the steering head entirely. Before cutting I'll check the swinging-arm axis is perpendicular to the frame centre-line and correct if necessary. The swinging-arm axis will then be the datum to work from to establish the new mounting points for the wishbones are parallel to that.
I'm aware that tele's were originally fitted to Commando's but as long as the front wheel trail and wheel base is fairly close to the original I don't for see any problems, unless anybody knows better - I'd be grateful for any more input.
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Anything's possible given enough time and engineering nous, but it seems like one quick step in making a beautiful bike into a right ugly mongrel.
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Beauty is subjective, personally I think the BMW design is a nice looking bit of kit. That it will out perform any telescopic is the main reason for the swap and performance takes priority over looks as the bike regularly does annual mileages of 5 - 6,000 miles. It dosen't do shows and I like mongrels!
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More on the reasoning of the duo-lever suspension choice over telescopics. I'm of the opinion that nature is the greatest engineer. Millions, if not billions of years in research and development which continues to this day. The Norman Hossack design uses natures designs. The human leg, for example, consists of load bearing members (bones) articulated joints (ankles, knees) and spring/damper units (muscles).
I cant think of any example in nature where a telescopic design has been used to provide load bearing with sprung damping.
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You do whatever you want, but if you want a seriously well-engineered motorcycle, why not just buy the whole BMW and have done with it?
The tele forks are of their time, the Commando engine stretches back to the 1940s, and the Isolastics back to the 1960s. You think the bike is going to be somehow transformed into something it's not by grafting the BM front end on?
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Call me rude and cynical, which I am, but if you have the skill to safely carry out these massive modifications, why are you asking other people instead of doing it and then showing it off?
Do you think this is some modification that's done a lot?
I am sorry if it offends you but I don't really care, bike forums are full of theoretical mechanics dreaming up these schemes trying to make a silk purse out of a sows ear, or a GPwinning bike out of a 1956 Pride and Clarke reject.
Do it, ride it,then show it off if you don't die on it.
By the way have you read your insurance quote where its asks "has this machine been modified in any way?"
Good luck, bring it back later.
telescopic design has been used to provide load bearing with sprung damping.
It's a machine not an animal, and 5000k mile a year [or 95 a week] is nothing, I used to do well over a 1000 a week as a long distance despatch rider in the 1980s, on a RT BMW, and a Honda CX, funnily enough both had the despised tele forks.
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I'm not stupid enough to think I cant learn things from somebody with more experience or knowledge than myself, hence the request for advice. I like my Commando. I've owned it since 1987 and have always improved things that I was not happy with, hence the BMW front end.
The topic has obviously annoyed both of you so why not stop reading any further postings. If you don't really care why the f#ck are you posting?
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Another smart arse tetchy one.
If you don't really care why the f#ck are you posting?
why are you showing off with your wet dreams?
you had good advice, viz why bother?
try one of the blobber custardizing sites,they are good at building junk out of good bikes.
Or better still the Norton Commando site they'll love you.
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'Why bother'? was a question, not advice. I'm bothering because the Hossack fork design gets rid of all the problems associated with telescopics. It'll make it a better bike to ride, faster into and through corners, smoother all round. First thing to go when I bought the bike was the appalling front brake (Why bother?) I've now got switch gear and handlebar controls inc. master cylinder off a Honda CBR600 - far better than the standard junk and cheaper.
Tetchy? Your the one who chimed in whingeing about people modifying their bikes. There's too many people like yourself on forums harping on about what they used to do - probably because now they do sweet F.A, apart from droning on about when they were droning up and down motorways doing a 1000 miles a week. I bought my bike to ride, and if, in my opinion things need changing then they get changed. Couldn't care less about the sanctimonious arses towing bikes to rallies and then criticising somebody who's ridden their bike there because they've got Japanese spark plugs or non-standard light bulb.
Get the picture?
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Get the picture?
Oh yes. The picture of you I had already is spot on.
I'm, nor is anyone else whinging about what you do to your bike I couldn't care less.
Couldn't care less about the sanctimonious arses towing bikes to rallies and then criticising somebody who's ridden their bike there because they've got Japanese spark plugs or non-standard light bulb.
yep, that about confirms what I thought, you belong on a blobber site. You are just one of those who want to show off their mechanical wet dreams and do not have the skill to do it.
Do come back soon and show me how wrong and misguided I am when you have finally carried out all these modifications in order to do your 95 ::)miles a week.
I will then grovel accordingly, but don't be too long son, 52 years of riding experience under my belt this year, I shan't be around for ever.
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Whatever you say. Hopefully some one will post something relevant to my original question.
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Hold your breath while waiting.
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Simon, not being nasty, but when I first read your post I thought you was joking. It's sort of like coming here and saying ... Hey I've got a featherbed manx norton that I'm going to put a cantilever rear end on. The reaction you received was justified when you want to perform an abortion on a classic motorcycle. I only hope you're not planning to slice the cylinders down the middle, and stick them out each side of the motor.
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he's only got a frame,probably not got the forks yet or the rest of the bike.
It's a shame to ridicule a fellow rider but I have met a lot like this over half a century on bikes, which is why I get very cynical.
There was a bloke on another well known site who was constantly asking daft questions about how to build bikes from the most bizarre parts, he was a fat burger chef who did not even have a bike license, or abike, even when he was offred one for free he came up with excuses.
I lost patience with him much quicker then the others, then again I was in the bike trade and had met many like him.
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Oh yeah, I remember that now.
On the same site they're currently discussing to the nth degree how to remove a head race. Dremels, multiple pullers, strange contraptions and turning up a threaded bar.
How did anyone get on before the days of t'Interwebby, and advice from random school teachers and retired opticians?
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It's only a Commando, there are thousands about.
If he's serious about it, why not? Other than that it's probably a waste of his time.
Better than turning it into a "bobber".
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I left off contributing to that site years ago, but to look in to watch the various spats going on .
Its a sign of its standards how a post about constipation drags on.
The head race saga is amusing in the ineptness or complication of the advice given. a foot long 1/2 steel bar, with a good square edge down the head stock should find enough of a lip to get a purchase on and knock it out.
although why he is replacing genuine triumph parts with new pattern ones I can't imagine.
Another source of amusement for me is swinging arm bushes on pre 70 Triumphs, There is a split in the thinwall bush, I used to find that and had an LE Velo clutch pushrod, ground to a chisel edge which would fit into it at the top and loosen it enough to pull out.
I have other Triumph short cuts with ignition timing, CB points oil seal relacement, clutch alignment, oil tightness, gearbox selector indexing and so on, but I gave up passing those tip on for free because so many cannot accept a solution that does not involve a lot of BS and hype.
I have come to the cynical conclusion that lots do not want to fix their bikes but to show off what they think they know.[but don't]
So it's not that the commando guy is a dreamer, just that if he was up to such major modifications he would not be asking the Internet surely? Welding course, oh yes. as long as I don't have to ride on it.
My heroes are guys like the late great Malcom Saggers an engineer of the old school for whom there were no problems only solutions, he could make anything; same as the older guys, retired toolmakers and the like that can turn out working radial aero engine models with a model engineers lathe and a file.