According to this http://www.engineeringtoolbox.com/thermal-expansion-metals-d_859.html SS is 70% of Al ?
Centre of flywheels and lateral centre of weight for a twin engine.
- Thread starter Monkeypants
- Start date
According to this http://www.engineeringtoolbox.com/thermal-expansion-metals-d_859.html SS is 70% of Al ?
ok, maybe approaching is the wrong word. How about 1/2 way between most ferrous steels and al?
I recall that some Vincent owners have switched the clutch pushrod to SS in order to come closer to the AL. cases for expansion. That way less slack shows up in the clutch when hot.
I recall that some Vincent owners have switched the clutch pushrod to SS in order to come closer to the AL. cases for expansion. That way less slack shows up in the clutch when hot.
Why use stainless steel, when they can be made of dural with hardend ends added?
that's one better alright.
I've been looking at the Egli frame vs Vincent UFM/RFM and can see why some egli builders would not have seen the need for the rear head bracket connection.
Done this way the engine is still hanging from the top spine by two cross bolts, same as a standard Vincent except the rear Egli hanger cross bolt is the swing arm bolt, which is one size up from the Vincent head bracket cross bolt.
Also, looking at the standard Vincent by comparison, there is not a great deal holding the wheels in line with each other against forces of torsion. It all comes down to the 2 head mounts, which the rear wheel has great leverage against thru the height of the engine. There may be a little added torsional rigidity found in the Vincent springbox/shock absorber to RFM connection, but I think not much.
When you look at it, it is really amazing that a standard Vincent works as well as it does, and yet they do work quite well. In a way they are the very opposite of a Featherbed frame, which is all about holding the wheels firmly in (almost) the same plane when cornering.
So on the Egli, those two little struts that angle down from the top spine to intersect the rear member of the triangle very near the swingarm bolt must give the bike a lot of Torsional rigidity. When the front wheel it tipped over on it's side for cornering, the spine is rolled with it thru the headstock connection. The spine takes the swingarm and rear wheel firmly with it by the connection of these two strong braces, one of which will be in compression, the other in tension.
I've been looking at the Egli frame vs Vincent UFM/RFM and can see why some egli builders would not have seen the need for the rear head bracket connection.
Done this way the engine is still hanging from the top spine by two cross bolts, same as a standard Vincent except the rear Egli hanger cross bolt is the swing arm bolt, which is one size up from the Vincent head bracket cross bolt.
Also, looking at the standard Vincent by comparison, there is not a great deal holding the wheels in line with each other against forces of torsion. It all comes down to the 2 head mounts, which the rear wheel has great leverage against thru the height of the engine. There may be a little added torsional rigidity found in the Vincent springbox/shock absorber to RFM connection, but I think not much.
When you look at it, it is really amazing that a standard Vincent works as well as it does, and yet they do work quite well. In a way they are the very opposite of a Featherbed frame, which is all about holding the wheels firmly in (almost) the same plane when cornering.
So on the Egli, those two little struts that angle down from the top spine to intersect the rear member of the triangle very near the swingarm bolt must give the bike a lot of Torsional rigidity. When the front wheel it tipped over on it's side for cornering, the spine is rolled with it thru the headstock connection. The spine takes the swingarm and rear wheel firmly with it by the connection of these two strong braces, one of which will be in compression, the other in tension.
Yes, I think the engine does provide some rigidity here or the bike wouldn't work at all. I'm also pretty sure there is a much greater degree of cornering flex in the Vincent UFM/RFM setup than in something like a Featherbed. I expect the Egli type frame will also have more torsional rigidity than the Vincent RFM/UFM.
Thinking of distance from the pavement (bottom of rear wheel) to the head lug as a 2 foot long wrecking bar (roughly 12" wheel to axle plus another 12" or so vert. distance swing arm to head lug) prying on that front head lug which is 2.75"" wide or, 1.5" or so for the later type RFMs, then one can see where some flex comes from.
On the other hand, the Vincent setup works just fine for going down the road.
Thinking of distance from the pavement (bottom of rear wheel) to the head lug as a 2 foot long wrecking bar (roughly 12" wheel to axle plus another 12" or so vert. distance swing arm to head lug) prying on that front head lug which is 2.75"" wide or, 1.5" or so for the later type RFMs, then one can see where some flex comes from.
On the other hand, the Vincent setup works just fine for going down the road.
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I don't know if I've missed it, but I haven't read where you've considered the extra bending moment you're putting on the swing arm/RFM - Double power = double pull in chain, and you're moving the chain further off centre - only 9 ish mm but that's 10% on the bending radius as well.
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Howard ,I have thought about the extra power here and decided to use larger dimension stock for the swing arm. I have some 1.25x 2.5 inch x.080 flat sided oval SS 316 tubing for the main swing arm beams. This was very difficult to find in SS. I finally found a supplier on the Isle of Man. Other than that I found one supplier somewhere in the US, minimum order 200 feet.
I hadn't thought about the extra bending from the chain position, good point. Will endeavour to make the swing arm as laterally stiff as is reasonably possible.
Fortunately the Vincent or Egli swing arm is quite short. This particular swingarm can be made with an extra long rigid section at front. The GSXR wheel is only 24" diameter so this leaves extra space at front for the filled in portion.
I hadn't thought about the extra bending from the chain position, good point. Will endeavour to make the swing arm as laterally stiff as is reasonably possible.
Fortunately the Vincent or Egli swing arm is quite short. This particular swingarm can be made with an extra long rigid section at front. The GSXR wheel is only 24" diameter so this leaves extra space at front for the filled in portion.
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As well as the bending moment on the swing arm/ frame overall, there is also the extra load on the chain adjusters at the axle end. Have you considered what you might use there? I personally detest the sliding block things with long bolts/ studs hanging out of the tail end of the swing arm tubes & am going to use eccentrics on the final build.
With the 2.5" tube there would be room for 60mm od eccentrics which should give a reasonable amount of adjustment. (Dont you love mixing the units?!!) I know that your rounded tube edges will add to the complication, but thats what Vincents are all about isnt it? Who was it that pointed to a twin timing chest & said "inside there sonny, is a whole bunch of solutions to problems that didnt exist"!!
With the 2.5" tube there would be room for 60mm od eccentrics which should give a reasonable amount of adjustment. (Dont you love mixing the units?!!) I know that your rounded tube edges will add to the complication, but thats what Vincents are all about isnt it? Who was it that pointed to a twin timing chest & said "inside there sonny, is a whole bunch of solutions to problems that didnt exist"!!
Haven't given much thought to the chain adjusters yet. The adjusters on my 490 Maico might be a good set to copy. They are subject to a lot of force, as is the rider on that brute!