Featherbed frame design went against all engineering princip
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Re: Featherbed frame design went against all engineering pri
http://en.wikipedia.org/wiki/Sunbeam_S7_and_S8
The early versions were somewhat sedate in performance,
and in addition had a slightly weak shaft final drive unit.
Not that the BMs (an obvious competitor) of the same period were ripsnorting sports bikes either.
(nor many immediate postwar bikes, really).
Many being quite small single cylinder bikes.
But we diverge, muchly, from featherbeds and isolastics....
84ok said:
http://en.wikipedia.org/wiki/Sunbeam_S7_and_S8
The early versions were somewhat sedate in performance,
and in addition had a slightly weak shaft final drive unit.
Not that the BMs (an obvious competitor) of the same period were ripsnorting sports bikes either.
(nor many immediate postwar bikes, really).
Many being quite small single cylinder bikes.
But we diverge, muchly, from featherbeds and isolastics....
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Re: Featherbed frame design went against all engineering pri
i was thinking more class? money? taste? in terms of 'gentlemen's tourers'?
kinda like a 'gentlemen's club'
it's interesting it took that long for rubber mounts to be tried out on bikes and apparently norton was the only other attempt up to that time,
i guess you could say harley took off with it
i was thinking more class? money? taste? in terms of 'gentlemen's tourers'?
kinda like a 'gentlemen's club'
it's interesting it took that long for rubber mounts to be tried out on bikes and apparently norton was the only other attempt up to that time,
i guess you could say harley took off with it
Rohan said:
Re: Featherbed frame design went against all engineering pri
They were quite expensive at the time.
Also very quiet and refined.
Designed as a brit challenger to the BMWs.
Shaft drive was also promoted as clean and maintenance free - supposedly !
Rubber mounts were a lateral thinking exercise to quelling vibes,
when most makers went for more mechanical solutions.
Commandos would have needed something entirely different in design,
if they hadn't adopted ruber doughnuts.
And they didn't have any spare such designs in the cupboard....
84ok said:
They were quite expensive at the time.
Also very quiet and refined.
Designed as a brit challenger to the BMWs.
Shaft drive was also promoted as clean and maintenance free - supposedly !
Rubber mounts were a lateral thinking exercise to quelling vibes,
when most makers went for more mechanical solutions.
Commandos would have needed something entirely different in design,
if they hadn't adopted ruber doughnuts.
And they didn't have any spare such designs in the cupboard....
Re: Featherbed frame design went against all engineering pri
Somebody asked the question so (as best as I can respond):
Commando – Some sort of 750, I think. No ID
Bare Frame: 28.5lbs
Frame and Swingarm: 36.5lbs
Frame, Swingarm and Isolastic Plates: 49.0lbs
Featherbed – 1955
Bare Frame: 32.5lbs
Frame and Swingarm: 40.0lbs
Frame, Swingarm and Engine Plates: 43.0lbs
The featherbed is missing the rear frame loop and it could be argued that I haven’t included all the commando isolastic rubbers, etc but enough for a simple comparison, I believe. You could close the gap with lightening, but the featherbed is 13% lighter to start with.
I do have photos of the two frames, but it's all too much to upload. The GT40 forum will let me upload from my PC. I don't understand why the same can't apply here.
Cheers,
Lance
Somebody asked the question so (as best as I can respond):
Commando – Some sort of 750, I think. No ID
Bare Frame: 28.5lbs
Frame and Swingarm: 36.5lbs
Frame, Swingarm and Isolastic Plates: 49.0lbs
Featherbed – 1955
Bare Frame: 32.5lbs
Frame and Swingarm: 40.0lbs
Frame, Swingarm and Engine Plates: 43.0lbs
The featherbed is missing the rear frame loop and it could be argued that I haven’t included all the commando isolastic rubbers, etc but enough for a simple comparison, I believe. You could close the gap with lightening, but the featherbed is 13% lighter to start with.
I do have photos of the two frames, but it's all too much to upload. The GT40 forum will let me upload from my PC. I don't understand why the same can't apply here.
Cheers,
Lance
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Re: Featherbed frame design went against all engineering pri
The Pre war models did not need rubber mounting.
The S 500cc twin models from 1946 were rubber mounted because they were a failure, almost un ridable due to vibration.
Those first (S7) models were returned to the factory and a remedy had to be found, it came in the form of rubber donuts, one at the front of the cylinder head, one under the rear of the gear box, a snubber each side of the engine mounted low (0.020" clearance) and a head steady of sorts at the rear of the cylinder head.
This solved the vibration and they went back in to production until 1956 so some 22 years before isolastics.
One of the small (two stroke) Ariel's may have has rubber mounting ?
wakeup said:
The Pre war models did not need rubber mounting.
The S 500cc twin models from 1946 were rubber mounted because they were a failure, almost un ridable due to vibration.
Those first (S7) models were returned to the factory and a remedy had to be found, it came in the form of rubber donuts, one at the front of the cylinder head, one under the rear of the gear box, a snubber each side of the engine mounted low (0.020" clearance) and a head steady of sorts at the rear of the cylinder head.
This solved the vibration and they went back in to production until 1956 so some 22 years before isolastics.
One of the small (two stroke) Ariel's may have has rubber mounting ?
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Re: Featherbed frame design went against all engineering pri
maybe the admin/mods will respond, usually comes down to money and how a site is run,
the main issues are, usually it is harder for folks to post pix but way worse is great pix/info that are not hosted on this site can and often disappear
LanceH said:
maybe the admin/mods will respond, usually comes down to money and how a site is run,
the main issues are, usually it is harder for folks to post pix but way worse is great pix/info that are not hosted on this site can and often disappear
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Re: Featherbed frame design went against all engineering pri
prob a bunch out there just not generally known, pretty sure the yamy rd350 from the early 70s was rubber mounted
then there is the 69 cb750 and all the first disc brake hoopalah and just ran across this recently for the first time
http://en.wikipedia.org/wiki/Douglas_%28motorcycles%29
Time Warp said:
prob a bunch out there just not generally known, pretty sure the yamy rd350 from the early 70s was rubber mounted
then there is the 69 cb750 and all the first disc brake hoopalah and just ran across this recently for the first time
http://en.wikipedia.org/wiki/Douglas_%28motorcycles%29
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Re: Featherbed frame design went against all engineering pri
I don't remember with the Yamaha RD350 but the Suzuki 750GT of that period had silent bloc type bushes (steel tube with a rubber damper molded around the inner sleeve) but they were mounted in the engine case for the mounting bolts to pass through (You could bore the 1974/ 1975 Kawasaki H2 engine cases to fit them)
Disc brakes are a whole other thing, some designs were to advanced thinking for materials available at the time.
Upload pictures to any one of the FREE websites and post them, its not 1949.
I don't remember with the Yamaha RD350 but the Suzuki 750GT of that period had silent bloc type bushes (steel tube with a rubber damper molded around the inner sleeve) but they were mounted in the engine case for the mounting bolts to pass through (You could bore the 1974/ 1975 Kawasaki H2 engine cases to fit them)
Disc brakes are a whole other thing, some designs were to advanced thinking for materials available at the time.
Upload pictures to any one of the FREE websites and post them, its not 1949.
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Re: Featherbed frame design went against all engineering pri
I can upload pictures to this site but still use Photobucket to post them here so someone else might be able to answer that.
I'm stilling trying to find in this thread what the engineering principles the Featherbed frame design went against.
Was it not having a top tube, having twin down tubes or a swinging rear arm perhaps, having curved cradle tubes seems like a stretch.
Was the Featherbed frame the first to have a swinging arm with twin (vertical-ish) coil over shock absorbers rising to mount on the rear sub frame ? (As we know today)
I can upload pictures to this site but still use Photobucket to post them here so someone else might be able to answer that.
I'm stilling trying to find in this thread what the engineering principles the Featherbed frame design went against.
Was it not having a top tube, having twin down tubes or a swinging rear arm perhaps, having curved cradle tubes seems like a stretch.
Was the Featherbed frame the first to have a swinging arm with twin (vertical-ish) coil over shock absorbers rising to mount on the rear sub frame ? (As we know today)
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Re: Featherbed frame design went against all engineering pri
pretty sure you must be a vp(?) member to upload pix here,
my opinion is that pix hosted on other sites, that show up here can for variety of reasons disappear (big time) anytime from this site,
it's a big loss anyway you look at it and ruins threads
i think that big bazooka backbone tube on the commando vs the small curved tubes used on the fb is the main argument,Time Warp said:
pretty sure you must be a vp(?) member to upload pix here,
my opinion is that pix hosted on other sites, that show up here can for variety of reasons disappear (big time) anytime from this site,
it's a big loss anyway you look at it and ruins threads
Re: Featherbed frame design went against all engineering pri
I think the comment arises from the view that the swingarm is unlikely to be held in alignment by twin cradle frame tubes, especially with a headstock sticking up in the breeze subject to sideways forces from a lever down to the front wheel. I don’t believe the usual featherbed engine headsteadys will resolve this. The solution was considered to be the backbone frame. I’m looking to modify my frame as Andreas Georgeades did to his featherbed (and BMW did to their knockoff) but still keeping the lower cradle tubes. To me, this modification stiffens up the headstock and frame and would probably stop the cracking that I read happens in the swingarm mounting plates? In my own case, because I plan to go Featherlastic, the swingarm forces bypass this area and are spread around the frame.
As far as curved tubes go, I think this issue is a red herring. In looking at curved tubes purely from a structural performance point of view, they can be made to match a straight tube by varying the diameter and wall thickness. Somebody mentioned this earlier. The solution may weigh more though, depending on the actual situation. A curved tube may be enough to clear an obstacle, where several straight tubes and joints (!) may be required to keep the tubes straight and then weigh more. Apparently Norton wasn’t too worried about curved tubes judging by the 1954 works Norton featherbed frame lower tube modification on yorkshireferret blog.
Cheers,
Lance
I think the comment arises from the view that the swingarm is unlikely to be held in alignment by twin cradle frame tubes, especially with a headstock sticking up in the breeze subject to sideways forces from a lever down to the front wheel. I don’t believe the usual featherbed engine headsteadys will resolve this. The solution was considered to be the backbone frame. I’m looking to modify my frame as Andreas Georgeades did to his featherbed (and BMW did to their knockoff) but still keeping the lower cradle tubes. To me, this modification stiffens up the headstock and frame and would probably stop the cracking that I read happens in the swingarm mounting plates? In my own case, because I plan to go Featherlastic, the swingarm forces bypass this area and are spread around the frame.
As far as curved tubes go, I think this issue is a red herring. In looking at curved tubes purely from a structural performance point of view, they can be made to match a straight tube by varying the diameter and wall thickness. Somebody mentioned this earlier. The solution may weigh more though, depending on the actual situation. A curved tube may be enough to clear an obstacle, where several straight tubes and joints (!) may be required to keep the tubes straight and then weigh more. Apparently Norton wasn’t too worried about curved tubes judging by the 1954 works Norton featherbed frame lower tube modification on yorkshireferret blog.
Cheers,
Lance
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Re: Featherbed frame design went against all engineering pri
I agree ,posting pictures here is a pain, i can send pictures [attachments] in seconds via emai..so why the hassel here?
I agree ,posting pictures here is a pain, i can send pictures [attachments] in seconds via emai..so why the hassel here?
84ok said:
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Re: Featherbed frame design went against all engineering pri
The Douglas's RA brake was different from modern brakes: the part that looked like a caliper had a female V cross-section and was forced onto the male V section of the rotor.
It was more like a compact dummy rim brake than a disc brake.
84ok said:
The Douglas's RA brake was different from modern brakes: the part that looked like a caliper had a female V cross-section and was forced onto the male V section of the rotor.
It was more like a compact dummy rim brake than a disc brake.
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