Max sustainable RPM?

Fast Eddie said:
Glen, how much power were these producing as they ‘putted by’ ?

With respect I’d say these two gentleman’s steeds seized due to heat caused by reasons other than power.
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This is true. There are many ways to wreck an engine!.
The 1950s British MC journalists encouraged this type of riding with their " Lowest Snatch Speed Test" that was part of nearly every road test.
What a silly test of a motorcycle.
When fueling up the Vin I still meet elderly fellows who will wander over and brag about snatch speed . (Stop sniggering in the back row)
One old guy told me " I had an Ariel Square four. It would pull from ten mile an hour to a hundred in top gear. What a bike. No other bike could do that , not even your Vincent!"
I just nod my head and start the bike.

Glen
 
There is more to sustainability than just RPM.
As mentioned above.
Max sustainable RPM?
 
hhh said:
It would be definitely true if going uphill, but on the perfect level, if the fat guy presents the same frontal area as the thin guy (unlikely I realize, but people come in all shapes and sizes) then the work would be the same given equalization of tire deformation via tire pressure.
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Wow!
 
worntorn said:
This is true. There are many ways to wreck an engine!.
The 1950s British MC journalists encouraged this type of riding with their " Lowest Snatch Speed Test" that was part of nearly every road test.
What a silly test of a motorcycle.
When fueling up the Vin I still meet elderly fellows who will wander over and brag about snatch speed . (Stop sniggering in the back row)
One old guy told me " I had an Ariel Square four. It would pull from ten mile an hour to a hundred in top gear. What a bike. No other bike could do that , not even your Vincent!"
I just nod my head and start the bike.

Glen
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Yep old magazines always used to publish lowest snatch speeds
I'm guessing in the very early days it was an important consideration with basic engines ?
I'm guessing it's a bit like the blokes who brag about their low idle speed (cam grinder speed)
 
baz said:
Yep old magazines always used to publish lowest snatch speeds
I'm guessing in the very early days it was an important consideration with basic engines ?
I'm guessing it's a bit like the blokes who brag about their low idle speed (cam grinder speed)
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I can think of more important snatch related specifications, like proper lubrication and clamping force.
 
Robinette calculators like the 8x figure for 2x speed.
This means that all I had to do to get my old 100 hp /100mph Cortina 1600 GT up to 200 mph is tune the engine for 800 hp.
I bought a rear spoiler for it instead. I think I got 102 out of it after that..

Screenshot_20230420_115340_Chrome.jpg
 
worntorn said:
Robinette calculators like the 8x figure for 2x speed.
This means that all I had to do to get my old 100 hp /100mph Cortina 1600 GT up to 200 mph is tune the engine for 800 hp.
I bought a rear spoiler for it instead. I think I got 102 out of it after that..

View attachment 105931
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Did it really only go 100 MPH? I got an Austin America to bury its "thermometer speedometer" with its 1275 cc engine modified with only a big valve ported head, 6% extra lift rockers, LCB header, electronic ignition and a DCOE45, and I'm pretty sure that was 100 MPH, but I could be wrong.

Edit: confirmed:
Max sustainable RPM?
 
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hhh said:
Did it really only go 100 MPH? I got an Austin America to bury its "thermometer speedometer" with its 1275 cc engine modified with only a big valve ported head, 6% extra lift rockers, LCB header, electronic ignition and a DCOE45, and I'm pretty sure that was 100 MPH, but I could be wrong.
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I held my buddy's BRAND NEW (14 mileson it) 1983 RX-7 PINNED WFO down 495.... 112mph 🐢
 
worntorn said:
Yes, 100 was about tops. The car was about as streamlined as a Humvee:)
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I'm quite surprised, compared to the America, which I think couldn't have been making more than about 75 HP. It's not exactly a sports car either. Must've been its "hydrolastic suspension" smoothing things out.
 
worntorn said:
This is true. There are many ways to wreck an engine!.
The 1950s British MC journalists encouraged this type of riding with their " Lowest Snatch Speed Test" that was part of nearly every road test.
What a silly test of a motorcycle.
When fueling up the Vin I still meet elderly fellows who will wander over and brag about snatch speed . (Stop sniggering in the back row)
One old guy told me " I had an Ariel Square four. It would pull from ten mile an hour to a hundred in top gear. What a bike. No other bike could do that , not even your Vincent!"
I just nod my head and start the bike.

Glen
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I once rode an Ariel Square 4 across Fisherman's Bend airstrip. It showed 105 MPH on the speedo. When I reached the cross runway where I useually started to brake, I realised the fence at the end of the runway was closer than usual. - General Motors had moved their chain wire fence. As I braked, I realised the fence was inside my braking distance. So I braked as hard as I could and went left. I did a U-turn at about 40 MPH on a runway which was about 100 Feet wide. I really thought I was not going to make it. I have actually seen a Square four road raced - pretty hopeless. They were a shocking bike. Our police used to ride them. When four of them led the Governor's car in a procession, they sounded good. I think that is the reason they had them.
 
My mahe is 2 months younger than I am. About 4 years ago he was living on the Mornington Peninsular. He had Suzuki Bandit 1200 which he use to ride down a side road at about 110 MPH past the farmers' gates. One day he was riding down the Mooraduc Road and guy in a Laborghini had a go at him. He just made it look stupid. He use to road race, and he road bikes which I would not. I don't likeriding bikes with make the ends of the straights look very narrow. Even In the old days, most bikes were faster than the fastest cars. In any case, when you speed on a motorcycle, it becomes more stable - cars do not.
I have been a a V8 Jaguar doing 280 KPH on Queensland Raceway. It was OK, but you are more at risk than you are when you do it on a motorcycle.
Many people feel more secure when they are in a car, but in a car on a country road, you are more likely to lose it, than when you are on a bike.
 
Drop a Vee Four inna Mk 1 twodoor , the post 70 have ports wotter bigga , by a eighth all round . Drop a Falcon Radiator in & a longer oil pump shaft 7 bigger sump ( Mk Iv modded )

And youve got more tourque than a Lotus Cortina , With stractors ( a beer jug is the Volume of the Boyer Triumph Length , Good for say 8.000 on the o.h.c. Pinto .) Staggered firing order
onnna da VeeFour , Vee Fours were usually FREE , $ 50 for a 100 mile overhauled one the circlip'd dropped & run No 3 & 4 big end . But with many free injuns , a cranks no worrie , mate .

Max sustainable RPM?
thesse things are more herodynamic , so are faster . Even the Aircraft Carrier Mk IV with the original gutless V 4 'd do 88 and blow off a then
BMW 528 . AND at 30 to the gallon . Corsair was 38 With a Capri V4 if kept over 65 . Did Lotus Corsairs for rallying in Greece . As Cortinas wernt there .
the Brakes & Box were flogged for the Lotus . 2000E is a better rear end , Struts are better too , as is Build quality & trim . AND'll fit 225 & 245 tyres . tho were 185 on 6's & 215s on 7's
On Mine .

Max sustainable RPM?


Max sustainable RPM?


With the bigger V6 oil pump ( one fits ) they run 80 psi and like running ' Flat Out ' at steady revs , so were popular in Jet Boats , where they WERE reliable . Bet the Ship .
 
Of Course TWO V 4s wont slow in down ( Like a P-38 Leyland / Rover 4.4 )


If Jim Clarke says so , who are YOU to dissageee ! ( Might not have the latter brakes springs shocks or engine & box ) .



SEBRING the CORTINA . The V 4's better WEIGHT DISTRIBUTION and with dual front bars , better balance , so'll 4 wheel drift much better , Passengers sometimes
grasp their gutter preparing to depart , if you ' open it up ' . out in the wildes .



SO Adequate Oiling and a Commando might stay togetter . They Ran 7.500 racing in 1970 , butted overhaul each metting or two for the front runners ,
Like Wother wouldon anyfing , if you wanna beea front runner . 7.000 and itmight get a season , or just one pulldown half through . If nothing fell off .
Therefore good wrenches were a prerequisette .
Not half assed drongo's .
 
Grandad said:
another adage I've used for bikes and cars ..... the most comfortable speed is when the speedo point to 12 - o - clock
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The 12:00 high observation on sustainable rpm for the preservationist minded rider is most likely not to far from the truth...🇬🇧 ✅
 
High Noon !
I have a 23T. 80mph is about 4100rpm. On the one hand, the engine is rotating more slowly. On the other hand, it's still doing the same amount of work as with a smaller sprocket.

I happily sit at 70mph / 3600rpm. It is smoother than my modern tourer. Not sure I'd be willing to test it to do this all day though, out of respect to the old girl.
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With mildly ported head & 32 Mk II Amals , that got a ' sweet spot ' of 80 , with the 2S cam . Which could be awkward in suberbia . On twenty free teef .

Cruise , observe . Opps . Pull down to 60 , observe the scenary . Observe the speedo . Back at 80 . OOPS . 23 gives almost the 19 T 4 th gearing , in 3 rd . Bout 112 mph .
With a 4.00 K 70 Aft , its higher . And'll do 50 foot rooster tails in wet gravel , if youre not carefull .

===========================================================================================================

Any Engine ' Outside Tolerances ' , is gunna go K L A N G , whereas a CAREFULLY RUN IN ONE , if it wasnt built on friday or monday , should stay together .

The W&S NORVIL Valve Springs are PROGESSIVE RATE - like a 55 T 100 R Tiger 500 - With a 8.000 rpm redline ( and 3 piece crank )
THESE are a LOT KINDER on the Valve Gear .

I believe it can get the Big Heavy Lifter thru to the Valve , working like a Newton's Cradle . Ran 16 Thou. ( 3 S ) Clearance .
Sound was as if it ' shot ' the valves open . The Initial Lifter Acceleration unrestrained , so it THREW the Pushrod -
Which ( itself ) threw the force up which the less gregarious ROCKER threw into the less initially ( with the Progressive Rate Spring )
linearly restrined ! ( or less witheld ) VALVE .

Sort of a matched enhanced actuation ! . far as I could tell . As In , if you get momentus missmatched - like in a WORN engine ,
the forces can be CUMULATIVE and the stress MULTIPLIED ,

Whereas if theyre all acting in harmony - it sounds like a well tuned orchestra - tho perhaps more vicious .

AND in days of yore , NIMONIC Valves were all the Rage , like in Bonnevilles .
The less thermal derangement in the chambers ( No nasty ' hot spot ' ) gave enhaced combustion , and hopefully removed the danger of pre ignition .
And Explosions.
Mechanical Ones .

From Miss Phased Combustion .

Which we can see is dissharmonious .
Like wot we were saying .

L J K's Thermo which wot theory , which is wot itis . If'n it isnt THERMMALLY CONTROLLED , itll never work. Properly .

Whereas if its thermally coplemetary , it should go like stink . If the Coils are up to it . And other things . And nobodys got a hangover .
 
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Matt Spencer said:
High Noon !


With mildly ported head & 32 Mk II Amals , that got a ' sweet spot ' of 80 , with the 2S cam . Which could be awkward in suberbia . On twenty free teef .

Cruise , observe . Opps . Pull down to 60 , observe the scenary . Observe the speedo . Back at 80 . OOPS . 23 gives almost the 19 T 4 th gearing , in 3 rd . Bout 112 mph .
With a 4.00 K 70 Aft , its higher . And'll do 50 foot rooster tails in wet gravel , if youre not carefull .

===========================================================================================================

Any Engine ' Outside Tolerances ' , is gunna go K L A N G , whereas a CAREFULLY RUN IN ONE , if it wasnt built on friday or monday , should stay together .

The W&S NORVIL Valve Springs are PROGESSIVE RATE - like a 55 T 100 R Tiger 500 - With a 8.000 rpm redline ( and 3 piece crank )
THESE are a LOT KINDER on the Valve Gear .

I believe it can get the Big Heavy Lifter thru to the Valve , working like a Newton's Cradle . Ran 16 Thou. ( 3 S ) Clearance .
Sound was as if it ' shot ' the valves open . The Initial Lifter Acceleration unrestrained , so it THREW the Pushrod -
Which ( itself ) threw the force up which the less gregarious ROCKER threw into the less initially ( with the Progressive Rate Spring )
linearly restrined ! ( or less witheld ) VALVE .

Sort of a matched enhanced actuation ! . far as I could tell . As In , if you get momentus missmatched - like in a WORN engine ,
the forces can be CUMULATIVE and the stress MULTIPLIED ,

Whereas if theyre all acting in harmony - it sounds like a well tuned orchestra - tho perhaps more vicious .

AND in days of yore , NIMONIC Valves were all the Rage , like in Bonnevilles .
The less thermal derangement in the chambers ( No nasty ' hot spot ' ) gave enhaced combustion , and hopefully removed the danger of pre ignition .
And Explosions.
Mechanical Ones .

From Miss Phased Combustion .

Which we can see is dissharmonious .
Like wot we were saying .

L J K's Thermo which wot theory , which is wot itis . If'n it isnt THERMMALLY CONTROLLED , itll never work. Properly .

Whereas if its thermally coplemetary , it should go like stink . If the Coils are up to it . And other things . And nobodys got a hangover .
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Hi all (again, again, again& again),
I’ve really got to stop piping up on this thread because I guess just about everything that could be said has been said and possibly a lot more, but I will just say this:
It seems to me that there are two distinct issues being discussed here, one is what wear is occurring as the result of horsepower being produced. As has been correctly pointed out, irrespective of rpms, the required horsepower at a given speed remains the same. In brief, the higher the rpm, the more power strokes per minute result in less shock loading onto vital components etc etc. As a very rough rule, horsepower at higher rpm is less damaging than at low rpm ie. don’t lug your engine.
The other factor which I believe is more significant in regards to the original question is what rpm can our engines continuously sustain before the centrifugal force and more importantly, the unbalance forces (and the myriad of harmonics that are associated with them), cause unacceptable wear and failure.
For a well designed engine built for large mileages such as a reciprocating aero engine or a modern truck engines, maximum power should occur way below the rpm where mechanical failure is likely through excessive revs.
Unfortunately that is not the case with our venerable old Norton motors which are capable of revving and developing power at a far high rpm than is conducive for longevity.
Given that the load and wear on components exponentially increases with angular velocity (rpm), somewhere there must be a sweet spot that provides sufficient power to enjoy our bike’s potential but also a degree of longevity. At the risk of repeating myself from previous posts, I believe that is between 4500 and 5500 depending on the rider’s perceived balance between speed and reliability.
I hope the above rubbish makes sense
regards
Alan
 
Yep. Dont use 8.000 . Some DID because They WOULD . on New COMBATS . after about the eighth time , it'd lost its edge . If Not all its oil through the ventilated cases .
Past 7500 is definately NO GO .
One in N O C was quoted as 100.000 miles . never taken past 6.000 , but regularly up in the mid 5's ON THE CONTINANT , and not at the traffic lights .
Out in the open , obviously . So as its getting plenty of fresh air . It Had DECENT air filtration , not the stock stuff .

5000 on 23 teeth isnt hanging around , in top . A Five Speed would be the best solution . A Extra Ratio on similar to std. gear spacing . For a WIDER speed range at ' std ' rpm's ,

Chaps .

n.b. 23 T and you need a car length clear , in front , getting underway . As your letting the clutch in . NOT sliding it . So youll run into it if you dont . Not City Gearing ! ! .
 
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