Various Seeley Frames (Mks)

Re: Various Seeley Frames (Mks)

Postby hobot » Mon Feb 04, 2013 11:53 pm

Matt that's what I call tire vector conflicts and mostly twists frame front to back. Similar to too stiff a wheel suspension can let tires bounce off surface, if frame can't twist enough one tire or the other will compensate with an instant of lost grip. Lost grip at one end or the other leaned lets the twist snap out of frame, if it rings as same rate as tire howl, so may the pilot next instant. Don't take much to compensate just couple of silly mm's for leaned tire twists to get grip enough to go faster, so by far the loads are all in same suspension plane as full upright. Don't think world has quite caught up with what's unbelievably possible as recent racer interview said when they made parts compliant enough to take up the twist then its not strong enough to last. Sounds like a job for Rubber Maid!

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Re: Various Seeley Frames (Mks)

Postby SteveA » Tue Feb 05, 2013 2:04 am

Matt Spencer wrote:The stiffness bit , theyre on abouZero Lateral complance , when leant over , locks the suspension . Gets a bit bumpy .

Theory being , if leant over at say 45 deg , a degree ( :oops: ) of sideways flex is necessary twixt frame & wheels ,
assumeing a flatish track with bumps & irregularities . Rather than banked speedway type ' turns ' .

Moto G.P. etc .


Sideways flex between the frame and wheel can be achieved at the swinging arm...neither Rickman nor Seeley arms were heavily braced like later designs, but the Rickman is typically much smaller diameter tubes and no bracing at all. I suspect the change to rubber bushes on the Rickman however was originally designed to give this flex, because none existed in the frame, in effect it 'amplified' the feedback from the contact patch to let you know you were near limits. I am pretty sure all Seeley frame designs have some flex built in, and they typically use a larger diameter (stiffer) swinging arm, letting the frame itself do the job of flexing in the turns. How far this carries forward to a modern Seeley replica versus an original is mute, since the tubing chosen often provides a stiffer frame! But again, this works with modern tyres (radials), which have different characteristics anyway.

The issue I came up against was the drive train compressing the rubber bushes longditudinally...forcing the wheels out of line under acceleration, specifically producing unwanted effects transitioning from braking to power mid corner. Phosphor bronze, or taper/needle rollers etc. limits that occurance.

A number of Rickmans have been fitted with stiffer braced box section swinging arms, maybe too stiff! Mine will retain a round tube item, but with a small cross tube brace, hopefully enough, and not too much, probably it won't make that much different because the arm is a little longer too, which would produce more flex....the length was to allow a wider tyre to clear the round tube, and to allow the swinging arm to still clear the frame....that radial tyre will also grip far more than a '70s tyre, but probably have its own sidewall flex.....

All of this really suggests that whilst interesting to consider how well things worked in the 60s/70s, you are playing with a rather different toy once you change rim sizes (dia and width), tyre widths, tyre constructions, tyre compounds, frame stiffness, swinging arm stiffness, typically stiffer springing and improved damping, and altered geometry at least from typically longer dampers etc. if not from altered head angle as well!
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Re: Various Seeley Frames (Mks)

Postby acotrel » Tue Feb 05, 2013 4:47 am

Why does the featherbed frame handle better if the rubber silentbloc bushes in the swing arm pivot are replaced with bronze bushes ? If you think that is not true - try it.
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Re: Various Seeley Frames (Mks)

Postby SteveA » Tue Feb 05, 2013 6:05 am

acotrel wrote:Why does the featherbed frame handle better if the rubber silentbloc bushes in the swing arm pivot are replaced with bronze bushes ? If you think that is not true - try it.


Alan, I have no expereicne of the featherbed, and its not even what I am saying about a Rickman, moving to Phosphor bronze, or today some form of impregnated nylon, is a good idea because it eliminates the swinging arm twisting longditudinaly in the frame under power application.

Seeley used bearings at the swinging arm pivot in any case, so he knew something, and one has to assume any flex in a Seeley is part of the frame design or its implementation.

I do question if the degree of flex of the original design is unnecessary/undesirable today considering tyre construction?

Those of you with Seeley MKIIIs seem to describe excess flex in any case! The MKIIs seem to have less inherent flex, and I am suggesting that a newly manufactured Seeley copy, with modern tubing, will tend to be stiffer, but it seems no one is complaining about that, so something changed....tyres...

Maybe the 'folk law' that says a Rickman is too stiff is outdated by modern tyre construction?

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Re: Various Seeley Frames (Mks)

Postby hobot » Tue Feb 05, 2013 8:31 am

Now this post has become educational to me with SteveA remarks. I've kept an eye on the best elite frame and swing arms and forks and tires improvement experiments and the racers detailed remarks about them - come to conclusion the ends [stem-forks, swingarm+mount] should be as stiff robust and light as possible so the twist-flex occurrs in the middle of tire patches near CoG. Tire width makes more handling difference than tire construction I've found, seems to have something to do with frame flex making tire walk around on its changing patch shape messing with the tire traction vectors back into frame flex. I definitely can go faster on robust modern frames and fat hot race tires, up till edges of handling then the damn things skip out and shudder unpredictably on every little pavement imperfection and wind-lift-drop eddies. If they'd just twitch back to neutral w/o rebound then they'd just twitch too fast and too short for tires to notice, but the stiffer frames tend to ring so next twitch catches up with tire hysteria twitching and that can be all she wrote. CoG in long axis and vertical come into play here too, if bike lean changes when tires slip some or forks trying to road follow rather than steer, then its a corner cripple to me limited to RR tracks committed lines w/o reserves to power turn sharper harder for hazards or parking lot cones slowing rolling in the way.
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Re: Various Seeley Frames (Mks)

Postby Chris » Wed Feb 06, 2013 12:33 pm

Hi

As promised a 2002 photo of Dave Watsons Mk3, already a championship winner. Gary Thwaites being the man to beat.
I will have to have a look at mylaps & see how far the records go back.

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Re: Various Seeley Frames (Mks)

Postby Dances with Shrapnel » Wed Feb 06, 2013 1:11 pm

Thanks Chris.

Which goes back to the comments about racers migrating to the Mk2 for the Norton twins.

Looks like they may have been using cast iron barrels back then.
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Re: Various Seeley Frames (Mks)

Postby acotrel » Wed Feb 06, 2013 1:37 pm

'I am suggesting that a newly manufactured Seeley copy, with modern tubing, will tend to be stiffer, but it seems no one is complaining about that, so something changed....tyres...'

I've never felt my Mk3 frame flexing, but as a rider brought up in the era of the T1 compound Dunlop Triangular tyres, I probably dont apply as much stress as many others. I would not have thought that the bar I've fitted instead of the 'ladder' at the front of the motor would be enough to stop flexing if it was going to happen. I don't believe the frame materials have changed that much, and I would only expect modern chrome moly tube to be less likely to crack due to vacuum degassing technology used in manufacture.
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Re: Various Seeley Frames (Mks)

Postby acotrel » Wed Feb 06, 2013 1:39 pm

Thanks for the photo - another one for my collection.
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Re: Various Seeley Frames (Mks)

Postby Dances with Shrapnel » Wed Feb 06, 2013 2:09 pm

acotrel wrote:I've never felt my Mk3 frame flexing, but as a rider brought up in the era of the T1 compound Dunlop Triangular tyres, I probably dont apply as much stress as many others. I would not have thought that the bar I've fitted instead of the 'ladder' at the front of the motor would be enough to stop flexing if it was going to happen. I don't believe the frame materials have changed that much, and I would only expect modern chrome moly tube to be less likely to crack due to vacuum degassing technology used in manufacture.


From where I sit there is plenty of anecdotal evidence out there on the flexing attributes of a Mk3. No doubt, people have been very successful on the Mk3's (as Chris has illustrated above by example) but it seems like there is a general migration to the Mk2's for the Norton heavy twins. Again, the reasons I have been told was greater stiffness (or maybe it was greater durability). This is what Steve Maney recommneded I use and that was in maybe 2003. Would like to get some more feedback on this as to exactly why.

I agree that the modulus of steel tubing for frames (steel) is more or less constant and that any change in stiffness is attributed gauge of the tubing, section of the tubing and/or subtle design differences. I would like to think that the more modern tubing offers better durability.
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Re: Various Seeley Frames (Mks)

Postby Chris » Wed Feb 06, 2013 3:20 pm

Hi

Its intresting to note the comments about the various Seeley frames. From a personal view point my Mk4 handles the best, depending on where you place your weight you can alter the handling, the balance seems perfect. The Mk2 I believe has become the frame choice for the Commando engine. Now, when you juggle these comments about, I have to believe that Steve Maney may have lead this drive! When I met Steve & for that matter Martin of Minnovation, they were racing Commandos in featherbed frames. When I first saw Steve on his Seeley Commando at 3 sisters circuit in Wigan in 93 or 94 (probably 94) it was housed in a MK2 frame. Steves & Martins bikes are just quality. The finish & bling!! not to mention the racing success has probably driven the use of the Mk2 frames being used with Commando engines. Now as to the Mk3. Mine is a road bike fitted with an 850 engine 4S cam Dellorto pumper carbs & a ported head. When it was last on the road it took some getting used to. I had fitted a 100 front with a 120 rear (Garys suggestion) to much tyre. You had to throw it into roundabouts & give it throttle. A change to narrow tyres changed it to a really pleasant bike to ride. In under 8000 miles the frame tubes cracked where the mounts were welded to fit a headsteady. Now I have always believed that this was due to the welding being improperly done (wrong type of weld) I have recently had the frame repaired & have found cracks in the headstock to top frame tubes as well as the nearside tube before the bottom loop. So again I believe the MK2 as a full loop has gained popularity as it is perseved & probably is, a stronger frame. When I spoke to Roy Thursby who framed the Ducati TTF2 bikes he told me that the Mike Redfern bike, that he helped construct (based on a MK3) caused massive problems as an 850 (with the frame pulling apart) & that they never had any trouble with it as a 750. The family recently restored the bike after finding it in Canada & it needed a lot of work doing to it.
However as Acrotel keeps saying. If you get the chance to ride a Seeley be it a MK2 Mk3 or a MK4, take it :D they are great bikes to ride/

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Re: Various Seeley Frames (Mks)

Postby SteveA » Thu Feb 07, 2013 2:46 am

Chris, your Mk4 is a very easy bike to ride (of course its the only Seeley I have ridden!). very stable and no toticeable flex at the speeds I rode it at, very good around Anglesey in particular, a twisty track....

That is even with me having trouble making gearchanges due to low seat height and gear lever angle, excess stiction in the forks and a front tyre too big for good turn in......trade off being braking performance on the tyre....

I have said before that all of the Mk3s I saw in the '70s had cracks in them, mainly around the rear engine mounting points and swinging arm area.....not heard of cracks around steering head before....head steady may have contributed?

Regarding tubing on new Mk2s, maybe they are using greater tube wall thickness as well?, for increased durability....

Roy Theresy told me about the Redfern bike, and I saw it in Gedinne last year....looks good now, but apparently it was in a sorry state....
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Re: Various Seeley Frames (Mks)

Postby Dances with Shrapnel » Thu Feb 07, 2013 7:11 am

Thanks for the feedback Chris and SteveA. Just trying to cut through the chafe a bit on the qualities of the different Seeley Mk's.

I do recall Keith Stephenson asking me what I was going to use the Mk 2 frame for; he suggested a heavier tube wall thickness if it were to go on the street but mine is for the track. Keith was also quite adamant about narrower profile tires; he said if I went with a wider profile it "would spoil" the handling.
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Re: Various Seeley Frames (Mks)

Postby marinatlas » Thu Feb 07, 2013 7:20 am

Hi Dances , which tyres profiles does he advised ....?
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Re: Various Seeley Frames (Mks)

Postby Dances with Shrapnel » Thu Feb 07, 2013 7:43 am

Well this conversation with Keith goes back nearly a decade so I do not recall the particulars and not sure if he ever mentioned specific profiles but I can give some context.

When discussing this with Keith I mentioned starting with the same profiles Steve Maney was running on the 750 Mk2 which was close to if not identical to an AVON AM23 Supervenom 130/650 VB18. So I would say that this rear profile was too wide for Keith's liking. I ran it and no complaints from me or other riders. We have since switched to a Dunlop 3.75/5.00 18 rear and 3.50/3.25 18 front and the combination works well.

The 500 Seeley Mk2 has a 2.75/3.75 18 front and 3.50/3.75 18 rear; both Dunlop. It is a much more nimbler feel than the 750 Mk2 but may also be due to lower overall weight as well as different weight distribution and maybe a more aggressive rake and trail. The 500 literally drops into a turn and really startled me when I took it out for the first time.

I hope this helps.
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