Featherbed frame design went against all engineering princip

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Re: Featherbed frame design went against all engineering pri

I noticed that there are two common grades of SS - 18/8 and another similar except containing molybdenum. I wouldn't have thought that a motorcycle frame maker would be big on materials. What do you think they would be using ? I've never heard of stainless steel being used for a frame prior to this. By riding the frame to destruction, what I mean is - with stainless steel do you get brittle fracture ? I recently made an Egli replica out of mild steel, and ground off the front tank hold-down, which had been bronze welded. My worry is that if the frame fails, it might be instantaneous rather than gradual cracking and tearing - thus a big crash.
 
Re: Featherbed frame design went against all engineering pri

There have been a few stainless steel Eglis built in 304, the first many years and many thousands of miles ago. No reported problems.
Glen
 
Re: Featherbed frame design went against all engineering pri

hobot said:
Featherbed frame design went against all engineering princip
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Damn it !!

I wish you wouldnt keep publishing this photo. This woman caused me enough sleepless nights as a 14 year old. I dont need to be reminded at 61 !!!!!!!!!!! :shock:
 
Re: Featherbed frame design went against all engineering pri

Back in the b/w TV days my parents had control of TV so rarely got to watch Mrs Emma Peel [in UK M-asculine appeal] but only took a little of her character to spoil me the rest of my life too. Similar to the shocking performance my tammed isolastic Ms Peel delivered. I think the basic isolastic frame is one of the sleekest lookers ever and part of Ms Peel's appeal to me is how effective its old fashioned obsolete construction more than held it own against the best cycles and eager pilots familiar with the challenging roads here. Ms Peel was so good I'd rather ride her for multiple road orgasms one after another than a real date with Dianna Riggs in her prime, as I'd only be good for a couple of piston strokes ...

Reflect on how the isolastic frame uses engine as structural component w/o stressing the engine structure.
 
Re: Featherbed frame design went against all engineering pri

acotrel said:
worntorn said:
I thought that 18/8 stainless is austenitic and that physical properties after welding steel depends on the ratio of austenite to martensite. Is stainless steel OK for frames ? Has anyone ever ridden one to destruction ?
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As worntorn mentioned in his post, he used 304 grade stainless, which is very weldable, and quite good for formability.

18-8 is not a stainless specification like 304, 317, etc. It's a generic term for steels with 18% chromium and 8% nickel. All the 300 series alloys are therefore "18-8", but can have very different qualities depending on the other alloying elements.

The first monocoque Norton frame was fabricated in mild steel. Once they were happy with the design, the ones that were used on the race bikes were made in stainless. I have no idea why. In general, 304 can be formed into deeper shapes than mild steel before cracking problems arise, but I don't see that as being of significance in the monocoque designs. Maybe they just liked shiny things? Don't we all?

Ken
 
Re: Featherbed frame design went against all engineering pri

A while back I looked at a standard commando frame with a view to using my spare bits to build another bike. I did not go there. I would be more likely to use a featherbed frame, however I would much prefer another Seeley Mk3. Nothing about the commando frame looks right to me.
 
Re: Featherbed frame design went against all engineering pri

lcrken said:
acotrel said:
worntorn said:
I thought that 18/8 stainless is austenitic and that physical properties after welding steel depends on the ratio of austenite to martensite. Is stainless steel OK for frames ? Has anyone ever ridden one to destruction ?
Click to expand...
Click to expand...

As worntorn mentioned in his post, he used 304 grade stainless, which is very weldable, and quite good for formability.

18-8 is not a stainless specification like 304, 317, etc. It's a generic term for steels with 18% chromium and 8% nickel. All the 300 series alloys are therefore "18-8", but can have very different qualities depending on the other alloying elements.

The first monocoque Norton frames were fabricated in mild steel. Once they were happy with the design, the later ones were made in stainless. I have no idea why. In general, 304 can be formed into deeper shapes than mild steel before cracking problems arise, but I don't see that as being of significance in the monocoque designs. Maybe they just liked shiny things? Don't we all?

Ken
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I would have thought that having a nice shiny frame would be a minor consideration. I've never seen a stainless steel frame. How would you know if it was going to contribute to a catastrophic failure under duress ? It's OK if the frame cracks and slowly deteriorates more under control, however if the steering head snaps off in one quick incident - you are stuffed. With that Egli replica I have built, I still look at it very critically and am thinking on ways to slow the process down if it fails. The motor in that project should have a bit of go, so a crash from that source would probably be a biggie. If it happens slowly, you have a chance of getting off easily.
 
Re: Featherbed frame design went against all engineering pri

I'm confused, Alan. (Of course, I'm confused a lot anyhow :? ) Why do you think stainless frames are more likely to break catastrophically than ones made with other steel grades? 300 series stainless alloys are used worldwide for all sorts of welded fabrications in aerospace, automotive, marine, industrial, architectural, etc. uses. They are austenitic, but I don't understand why that's an issue.

Ken
 
Re: Featherbed frame design went against all engineering pri

Aside from the stiffness and strength of the 304 Stainless frame, I like the fact that a lug or tab can be added or subtracted here and there with just a polish to finish. No plating to redo or paint to repair.
But it is a lot of extra work to build a frame in stainless. It moves a lot during welding , so you must constantly check things, then weld on the side that needs pulling. Once finished it is very solid.

As far as concern's about cracking, I believe the original Manx frames were notorious for that, however this hasn't prevented riders from extracting full performance from those machines.
I have stood this bike on it's nose, rear wheel in the air from 110 MPH down to zero with the big GSXR twin disc on the front, no I'll effect on anything . So I will just ride and enjoy, not worry.


Glen
 
Re: Featherbed frame design went against all engineering pri

When a manx frame cracks, it doesn't usually totally collapse. If the material is susceptible to brittle fracture the failure could be catastrophic. It depends a lot on the design of the frame. The old BSA A10 frames had a loop of sheet steel welded around the front of the steering head, so that if the frame broke while the bike was being ridden the collapse would be slower. I've seen the fork yokes completely break off a bike during a road race. The rider simply joined everything else which was rolling forward down the road. The Maxton Yamaha frames of the 70s had a Schraeder tyre valve fitted which was used to test for cracks after a race. The frame was pressurised, and if the valve did not hiss after a race, it was time to search for a crack.
 
Re: Featherbed frame design went against all engineering pri

Allan, I too don't understand how you have gone from having almost no knowledge of the large group of metals known as Stainless Steels, to deciding that a frame built out of any one of these metals would break in a catastrophic way?

Glen
 
Re: Featherbed frame design went against all engineering pri

When Alan gets a bee in his bonnet, there is no stopping him. !
 
Re: Featherbed frame design went against all engineering pri

If anything I'd think Norton was more concerned of rusting out failure inside than differences in stamina. We do know that some SS grades in engine mount -cradle fasteners have sheared but not same size carbon steel bolts. At some thickness for the load in bolts or sheet, SS should work a treat. Racers often give up long term endurance in frames and tire to get ahead but don't know if applies to monocoup Norton. Anyone know the weigh of Featherbed or the mono boxer? See if any clarity SS vs carbon steel in this reference article.
http://www.bssa.org.uk/topics.php?article=125
 
Re: Featherbed frame design went against all engineering pri

Worth repeating that most common grades of stainless are only about the same properties as mild steel.
Stainless does tend to surface work harden though, which can mask this a bit....
 
Re: Featherbed frame design went against all engineering pri

At the risk of moving even further away from featherbeds, I remember reading somewhere that the JPN "space frame" had a tyre valve inserted somewhere so that the frame could be "pumped up" with an airline to a known pressure, then routinely checked for any drop in pressure, which would equal at best a crack somewhere.

Back to the monocoque, I vaguely remember that the stainless one was the first one to be made, the rest were mild steel because it was easier to work. But I could be wrong!
cheers
wakeup
 
Re: Featherbed frame design went against all engineering pri

I'm testing Peel's OIF with vaccum and pressure from out in sun heat which did open up pin holes to weep or drip so had to JBW some more in many cycles so far. I've wondered about pressurizing a box structurea to stiffen it but don't know if that also makes more prone to fracture. Peel's boxed Al swingarm has 100 PSI in it planned. Showed it to a few retired engineers and active machinist who say should be fine. They make gas tanks by welding two or more flat sheets together then inflate with water pressure till splits, weld more and repeat till ends up the desired shape.
 
Re: Featherbed frame design went against all engineering pri

wakeup said:
At the risk of moving even further away from featherbeds, I remember reading somewhere that the JPN "space frame" had a tyre valve inserted somewhere so that the frame could be "pumped up" with an airline to a known pressure, then routinely checked for any drop in pressure, which would equal at best a crack somewhere.

Back to the monocoque, I vaguely remember that the stainless one was the first one to be made, the rest were mild steel because it was easier to work. But I could be wrong!
cheers
wakeup
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Other way round, actually. The first one was a prototype in mild steel, and I don't think it was ever turned into a race bike. The rest (four, I think, or maybe three) were all in stainless.

Ken
 
Re: Featherbed frame design went against all engineering pri

lcrken said:
wakeup said:
Back to the monocoque, I vaguely remember that the stainless one was the first one to be made, the rest were mild steel because it was easier to work. But I could be wrong!
cheers
wakeup
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Other way round, actually. The first one was a prototype in mild steel, and I don't think it was ever turned into a race bike. The rest (four, I think, or maybe three) were all in stainless.

Ken
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I thought I could be wrong and I was!!

hobot said:
I'm testing Peel's OIF with vaccum and pressure from out in sun heat which did open up pin holes to weep or drip so had to JBW some more in many cycles so far. I've wondered about pressurizing a box structurea to stiffen it but don't know if that also makes more prone to fracture. Peel's boxed Al swingarm has 100 PSI in it planned. Showed it to a few retired engineers and active machinist who say should be fine. They make gas tanks by welding two or more flat sheets together then inflate with water pressure till splits, weld more and repeat till ends up the desired shape.
Click to expand...

Pumping up the JPN frames, was done to a low pressure, maybe the same as a tyre, purely to enable detect leaks to be detected

At one stage I saw a method of making two stroke exhausts, moto-x ones, out of two accurately developed sheets of steel, which were welded together to form a sandwich, then they were pumped up using water. If the development was correct, the shaping was done the exhaust just needed tiddlying up at the cylinder end and the outlet end. Job done! Did take a fair bit of water pressure though.
cheers
wakeup
 
Re: Featherbed frame design went against all engineering pri

I thought that forming expansion chambers using water pressure is done in a steel die ? The header pipe can be difficult to make - the rest is not so bad just by welding cones. It is a current stumbling block with my other project bike.
 
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