Found. a true 70 Production Racer

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Thanks Ken. Which Bacon book is that - I've seen those pics, and details, but don't recall them all together like that.

Now, if we could find a period color pic of that bike.

And, as a rhetorical question, why don't we see ANY replica bikes built like that ??
Hmmmmm.


lcrken said:
This is the only other pic I've seen, from Roy Bacon's book.

Found. a true 70 Production Racer

Ken
 
Bernhard said:
There was the infamous remark by Peter Williams where Norton kept just 2 bikes specifically for the Brands Hatch Indy circuit that had their whole engine & gearbox mounted 5/8 inch to the left, so these bikes lapped this circuit 2 seconds quicker than anybody else.
You certainly couldn’t buy one of these :!:

How did this handle the chain being out of line ???
Wider swingarm ? Offset swingarm. ?
 
Rohan said:
And, as a rhetorical question, why don't we see ANY replica bikes built like that ??
Hmmmmm.

Well these pictures above have certainly given me some impure thoughts. :wink:

The oil tank in the later picture is interesting since I purchased an oil tank similar to (if not identical to) the one shown in the second picture. Any more pictures or specifications will be appreciated.
 
And another thing about that picture and spec sheet on the "Thruxton Cup" Racer..................

The brochure mentions a "modified rear suspension" so it looks like they no longer used the lay down rear shocks and now employ a more upright set of shocks.

Also read an obvious typo where fourth gear is listed as 1.105:1 and fifth gear is 1.100:1 NOT.
 
Dances with Shrapnel said:
And another thing about that picture and spec sheet on the "Thruxton Cup" Racer..................

The brochure mentions a "modified rear suspension" so it looks like they no longer used the lay down rear shocks and now employ a more upright set of shocks.

Also read an obvious typo where fourth gear is listed as 1.105:1 and fifth gear is 1.100:1 NOT.

Nice catch, John. I hadn't looked at the gearset ratios. I've never seen a Quaife 5-speed with ratios close to those. The usual A1H1 Quaife gearset of the '70s had either a 2.23 or 1.986 first gear ratio, although some others were available, and 1.654/1.351/1.105/1 for second through fifth. And I've never seen any Quaife AMC box with a fifth gear ratio other than a direct 1:1. Probably another victory for the marketing crowd.

Ken
 
Rohan said:
Bernhard said:
There was the infamous remark by Peter Williams where Norton kept just 2 bikes specifically for the Brands Hatch Indy circuit that had their whole engine & gearbox mounted 5/8 inch to the left, so these bikes lapped this circuit 2 seconds quicker than anybody else.
You certainly couldn’t buy one of these :!:

How did this handle the chain being out of line ???
Wider swingarm ? Offset swingarm. ?


I haven’t got the foggiest idea, as nobody appeared to ever noticed the mods on those 2 bikes, ever :!:

I can only conclude that the rear sprocket was off set with some spaces :?: :shock:
 
How does offsetting the engine and gearbox to the left decrease lap times unless it allows a bigger rear tyre to be fitted ? Sounds to me a bit like pumping the shockers up and down to get them warm, when you just happen to have a swing arm mounted fuel pump. Back in those days the tyre compounds would have been pretty crappy, so a loss of nimbleness with a fat back tyre to get better traction, would have been an acceptable option. These days on classic bikes the compounds available in even 19 inch tyres are so good there is no need to stuff the handling by fitting large profile tyres. The first 'gumball' tyres I saw in Australian road racing were in about 1971, and were American Goodyears which one of our top A Graders imported. They didn't become common until the mid-70s. Most of the Manxes running in Australian historic racing are still fitted with 18 inch wheels to fit those tyres , but there are two notable exceptions - one is the McIntosh manx that Cameron Donald rides with so much success - still has 19 inch wheels.
 
Hm did they have that much bigger tires back then for the OD rim sizes fitted?
Even w/o the LH offset a Commando can lean enough to foul the primary cover if one fitted. [rear sets only duh] If ya do it often, far and fast enough you can sense the slight bias of more mass on LH, which makes a fling down to that side a tad easier, though not any faster turning than the other way, so a nullity to me.

I suspect they actually shortened the cradle by 5/8" which is known to increase the Cdo sharpeness ease factor. This was a little secret Ken Augustine of Worlds Straightest Commando builder race trick.
 
Changing the wheelbase of a bike can have some strange effects. There was a Parilla 250 which my friends raced years ago, and is still here . It was the genuine production racer and only one was imported. Everyone who ever rode it, crashed it. It seems that the short wheel base was the reason - apparently one moment you would be on it going like the clappers the next you would be on the ground. In those days the common compound used was T1 in Triangular Dunlops, which were pretty treacherous on any bike, however the Parilla was something else again.
 
Ugh, we should abhor motorcycles that cripple and kill out of the blue. Ugh only one way to find out. Ken Augustine took me under his wing some years ago and no one but no one knows more about the oddities of Commando construction and correction, while still being an un-tamed isolastic, so not likely as good as the Becker/MacRae swashplate stablized isolastics. His shortened racers, two or 3 of em, ate up the field till power evolution eventually out horse powered em in the opens. That was during era they were considered world class race bikes not vintage class only. Ken and I went round and round on weather I should chop Ms Peel but I've not been able to upset her pressing loads higher than I thought possible yet nothing happened unpredictable at all. All's I can say is that kind of security can drive one insane past fear states towards THRILLED to Death addiction. I'm sticking with what works for me. Would be good to know if PR was really offset or shortened.
 
Hobot, I don't believe that motorcycles can successfully be dual purpose. If your bike is set up for riding on bitumen, it probably won't work well on dirt, and vice versa .
 
There is a whole genre of dual-purpose bikes, and some of them work very well indeed at both.

But we'd probably agree, a dual porpoise Commando sounds like a mythical odd beast indeed.
Although in hobot-land, anything is possible ?
 
acotrel said:
How does offsetting the engine and gearbox to the left decrease lap times

Brands Hatch is primarily almost all right hand turns, so having effectively more ground clearance on the right side could allow it to be heeled over further.
Which could perk up the lap times quite a bit. Providing the tires grip, like you say.

Does sound a little extreme, and outside the rules ?
 
OHHHhhh, yes indeedy if PR could lean further to needed side than others it'd sure have an advantage. Mystery solved for me. Wonder how they'd be shortened up a tad?

hobot, I don't believe that motorcycles can successfully be dual purpose. If your bike is set up for riding on bitumen, it probably won't work well on dirt, and vice versa .

Alan, I too once thought the same thing but boy howdy have I ever been converted by ole Peel whose real delay in finishing and fielding is directly related to mods for her primary purpose doing off road duties. Reflect on the supermotards which are MX bikes with 17 road tires instead of knobbies and good clearance to lean, or the salt lake pilots surviving a wild ride saying with trembling adrenalin they sure wished they'd had more practice on loose dirt and grit. Peel's 2" extended forks definitely gained lean clearance, so i can get her down low enough the hi side let go reactions don't continue into a full barrel roll. Ugh which I have done on Peel entering my drive way final crook with a 50' bank berm 2-3 tall I tend to take mostly side ways but got too hot and ground gave way whoowee ... SpALT. The crash cage is strictly for public risks and get stripped off for the track day pecking ordering and blower too if it hinders leans too much, though that again goes to the very hear of Peel being able to power steer by winding up frame with insane tire conflicts, no worry of some surprise trip down or fly up. Peel's rear is lifted 2" too for more high centering clearance pitching over sharp raven edges, but feel the same level of commitment blasting down faster than gravity for enough momentum to blast up steep far side with head light at belt buckle as it does flying into phase 3 and above turns. Peel OIF frame vent cap is one way in only d/t being upside down too often and me not being able to get up to attend to her right away. I hope I'm still in man mood enough to work back up to Peel's potential as its as close to scared to death as I've ever been and wanting to do it again and again. Peel is so different from regular isolastics and from modern super rigids I can't ride them to have fun like on Peel. Slowly moving her along.

I've seen the sport bikes and racers pull off some phase 3 4 and 5, which is type of steed I learned to on but also the see many close calls or crashes in those spots sometimes by same pilot that got away ahead the first few times around.

Bent these alloy bars to fit my style better
Found. a true 70 Production Racer


Found. a true 70 Production Racer
 
Wasn't the P11 a dual purpose steed, more or less - it came with dirt tires new even ?
 
Hi
Acrotel, Rohan is correct about Brands. Clearways especially would have the cases on the ground.
Norman White's proddie bike replica's featured in Classic Racer had the engine raised & moved over in the frame.
Lots of little tweaks done to proddie bikes back in the period. It was a big part of club racing for many years. Sadly not supported much in classic racing now. some people seem to be able to cope with dragging their pipes on the ground. It makes me pass buttons :D
Remember asking about the plates welded on the front of a proddie T150 frame tubes. Yep worn though. Then again you dont find many standard frame proddie tridents (besides the big bore engines in period) most Tridents had the frame hike. One of our champions of proddie racing had two on his garage wall the 2nd frame jacked the engine higher than the period raised frame due to modern tyres! ie super venoms in race compound. Nothing new under the sun.

Chris
 
Chris, I think I would increase the ride height before I would offset the motor and gear box to get ground clearance. The other thing that can be done is to get well off the s ide of the bike in corners and keep the bike more upright . We a lways had to do that woth the older tyres we ran.
Hobot, I question the riding style of riders like your Roberts etc. I know a lot of yanks were very successful on the bitumen after riding dirt, however I still believe the quickest way around a corner on bitumen, is to be 100% smooth and precise putting minimum sideload on the tyres. Once the wheels start sliding you become fully dependent on forces often outside your control. You might get a bit of advantage at times , however you are more likely to end up on the deck.The tyres on my Seeley are 8 year old Battle Axes, however I have never had to use them to their absolute limit, even when new. I'm an old fart used to riding bikes on which the tyres were horrible. So the bike stays more upright , and my moves are very quick and decisive. If you have a look at that photo on the RHS, you will see that the tyres are 19 inch T1 Compound Triangular Dunlops, and I am off the left side of the bike. The angle of lean is about the max for that setup, also the photo was taken at Mount Gambier in about 1971 before the non-skid surface was replaced. Actually, I always get a bit of a laugh when I look at that photo, it is so bad. If you did it wrong there you'd end up in hospital cut to pieces .
 
acotrel said:
Chris, I think I would increase the ride height before I would offset the motor and gear box to get ground clearance.

When you've set the ride height to the max, then you start offsetting the motor. ?
Every little advantage...

Wonder if thats within the rules ?
 
Ok then <> since this post has decayed into the life/death stuff such as riding as if on rails or jumping the tracks.

Unread postby Rohan » Sat May 04, 2013 6:17 pm
Wasn't the P11 a dual purpose steed, more or less - it came with dirt tires new even ?

The P11's were king of the hill for a while there and could gotten in street or off road race equipped tire and forks etc. Its still hard to top their torque to mass hits where it mattes in maneuvering below 100.

Two tires still in traction effect is fine until leaning past 45' then tis merely the launch phase to really get on with Ms Peel. Down to 45' its a pure power to weight and resistance contest not a handling strain tester. Below 45' the rules change with speed and power and wind and pilot position and bike CoG and tire width and road texture.

I fully agree drifting is for the birds or parking lot stunts, though its just natural to do in some turns as lines ya up for the exit the fastest to then pop up and hook up out of there. Alan this seems to be the limit you are describing on your Seeley that ends up pointing right - after exit to nail it more w/o any pilot effort but to set up the initial turn and hang on grinning at the wonder of it.
Getting off to one side does indeed allow same turn radius w/o further bike lean. But shoot I always want to lean further till no room for knee tight on tank or foot in folded up peg. The other thing I found wrong for me to hang off is I get going too fast to have time to change sides and the change of CoG and slight let off of load of pilot on bike upset the frame for a jitter that can escalate like the elites losing it. Besides I've no mass in my ass at'tall w/o a wallet and clip knife. If I get out of pure drag racer locked in back centered posture its to get ontop of the bike to move CoG closer in and more directly down on rear tire, as by then the rear thrust and lean has extended forks to limits and taken a lot of the traction effect away. But that just for going fairly slowly on THE Gravel, pasture or tarmac. When I let Peel's hair out we are locked together like lovers doing it doggie style. Peel does all the work though so I can just lay back enjoying it with just a twist of the wrist to urge her on.

Rising height works the best for lean fouling - witness the elites with pilot sitting like horse jockey's on tall stance animals. But if ya make bike too tall the extended out CoG of pilot hanging way off can suddenly lever the bike completely horizontal, swoosheroo right out from under. Peel will not do that with me centered on her, she will just drift as same angle w/o any more pilot effort, which is one thing I now know a really neutral handling bike should do.
No more effort to force down than to lift up and no effort to stay at what ever lean set. I do have to stablize the bars when drift or slides start but its even side/side short fast loads I don't need no stinking steering damper for, as those little short sharp reversals are the life saving automatic compensations flapping through compliant non rebounding isolastics harmlessly. My SV and the Ninja tend to trip down>increase angle with loss of traction, which drives forks and pilot bonkers. So when the sports bikes loss traction trying to turn sharper they go down while Peel just widens the radius, as long as I don't transition into faster handling phases, so I see drifting as boring to dangerous state to stay in. NOT TRYING to turn sharper is what you see in the video dramas, but still a faster way around in that loose sate, as hehe, they can't hook up sharper loads so do the next best thing.

Here's the low down on what I've found for my sharpest turning no matter the cylce - as every cycle has its roll speed to be able to lean over to max and to turn forks to max and to take power hook up to max, and there is no better forward hook up than bolt upright or for braking too, I brake upright straight toward inner edge of turn but only to slow enough to be on WOT before any leaning begins to shoot pass the trail braking zone of others, straight on till most open long section of turn comes into view, then toss it over, letting off throttle some if bike wants to fall over too far which of course hooks up a bit more acceleration by wheel momentum than just prior and helps lifts bike back upright by a hi side action thats lined us up to drag race towards next braking need or in longish sweepers - no brakes just another sharp as can be facet. To me the second worse state of a cycle is long held fixed leans on increasing power. The first is braking with any lean or fork turn. I later learned this is how the 125 guys on pointy tires do their turns too expect they can't jump rails.

Above covers my rolls but not pitch and yaw handling.
 
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