steep intake ports

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I remember Tony Foale from the '70s and frame design. It is really interesting to see him sharing his vast knowledge through social media these days, also check here for chassis info:

motochassis.com

Motochassis Introduction » Motochassis by Tony Foale

Motochassis is for those interested in motorcycle handling and chassis. Articles and illustrations on motorcycles and racing in general. It is the prime source for the book "Motorcycle Handling and Chassis Design" by Tony Foale and software packages for motorcycle suspension setup and analysis.
motochassis.com motochassis.com
 
SteveA said:
I remember Tony Foale from the '70s and frame design. It is really interesting to see him sharing his vast knowledge through social media these days, also check here for chassis info:

motochassis.com

Motochassis Introduction » Motochassis by Tony Foale

Motochassis is for those interested in motorcycle handling and chassis. Articles and illustrations on motorcycles and racing in general. It is the prime source for the book "Motorcycle Handling and Chassis Design" by Tony Foale and software packages for motorcycle suspension setup and analysis.
motochassis.com motochassis.com
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He was at least 10-15 years ahead of the game with his ideas on frame design
Rigidity, rake and trail ,his thoughts on wheel spindle diameter and rear suspension preload were an inspiration to me
Very interesting
 
There is probably an optimum angle for intake ports. At TDC on the stroke when both valves are open, there is a flow of mixture across the comubustion chamber and into the exhaust. The Kadency effect stuffs mixture back into the cylinder. An expansion chamber for a four-stroke probably would not fit on the bike. The flat top piston in a Commando motor is an advantage, when compared with Triumph motors, which usually have pistons with raised crowns.
The optimum downward angle on inlet ports probably cannot be determined on a flow bench.
Harley motors are a completely different concept to a Commando motor. Whichever you use, you need to build on it's strengths,.
On dirt, a Harley probably gets more drive than a Commando - the balance between slide and drive would be different, so the bike needs to be set up differently.
 
baz said:
He was at least 10-15 years ahead of the game with his ideas on frame design
Rigidity, rake and trail ,his thoughts on wheel spindle diameter and rear suspension preload were an inspiration to me
Very interesting
Click to expand...
I have read Tony Foale's book on frames and handling, and it seems to be correct about the effects of changing trail. He says at the extremes, the handling moves towards self-steering. However, he does not talk about over-steer or understeer. Manx Nortons oversteer if you gas them, when they are on a lean.
When I raced against them I never knew why they were faster in corners - then I rode one.
 

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Tony's float bowl solution is pretty elegant, I also noticed a martchbox remote float bowl in his pictures, but didn't see anything but a brief mention of it in his description. I remember seeing a similar high angle setup, with twin Amal MK2s (40 mm, I think), on one iteration of the Quantel Cosworth Norton. That was at a race at Daytona somewhere in the '80s. It had the carbs modified to allow the use of the remote float bowls. This isn't a great picture, copied from an old magazine article, I think, but it does show some details of the setup.

cosworth_13 x2.jpg


Ken
 
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Here's some slightly raised ports with straight mainifolds on my monoshock racer.


steep intake ports


There were a lot of other innovations on this bike. Some of them listed here.

https://jsmotorsport.com/norton-firsts-and-innovations-to-my-knowledge/


Below is the 1st version (1985) before I went to monoshock. You can see the carb angle and vents on the sides of the gas tank (tank was redesigned soon after). You can also see a large red breather hose to the sump. This bike was running well in the AMA Laguna Seca BOTT untill the Boyer ign crapped out.

steep intake ports
 
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It should be remembered that Tony Foale has a lot of experience with Aermacchi single racers, so is no stranger to what seems to many of us seems and odd angle!
 
The cables on the carbs of my Seeley 850 are wearing grooves in the bottom of the aluminium tank. I need to find some thin sheet rubber to glue under there, or I will end up welding.
 
A lot of this thread seems to focus on steep carburettor angle. That does not equal downdraught. Downdraught is all in port design.
 
acotrel said:
The cables on the carbs of my Seeley 850 are wearing grooves in the bottom of the aluminium tank. I need to find some thin sheet rubber to glue under there, or I will end up welding.
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Bicycles these days route a lot of cables through the frame tubing, so small diameter foam tubes are available to stop rubbing and rattling. Any well stocked bicycle store should have some that will work for you.
 
KiwiShane said:
I thought they were gravity feed 🤣
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I also thought this thread was about downdraught - perhaps it is not ? It would be difficult the get more down slope on the inlet ports. And I think they would be at the optimum angle anyway. If the motor is tilted more, the float levels in the carbs might be affected. The slightest bit too rich means slower.
I think Joe Craig was a very smart guy. It is difficult to improve a Manx engine. The Commando head was probably designed to perform with similar efficiency. The difference is very noticeable when you compare one with a Triumph 650 head.
However designing a Triumph head to be similar would be very difficult. I think one of the main things is the direction the ports point in the Bonneville head. You might get swirl, but in a Norton head, the inlet port points at the exhaust port which would provide a straight blast of mixture across the top of the piston when both valves are open at TDC. The Kadency effect might work much better.
 
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MichaelD said:
Old inner tubes are made for jobs like this. Maybe folded over if you need more thickness
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I am still using both of my old inner tubes inside my 23 year-old tyres. I cannot run the cables through there, they would twist around the axle and stop the bike.
 
acotrel said:
I also thought this thread was about downdraught - perhaps it is not ? It would be difficult the get more down slope on the inlet ports. And I think they would be at the optimum angle anyway. If the motor is tilted more, the float levels in the carbs might be affected. The slightest bit too rich means slower.
I think Joe Craig was a very smart guy. It is difficult to improve a Manx engine. The Commando head was probably designed to perform with similar efficiency. The difference is very noticeable when you compare one with a Triumph 650 head.
Click to expand...
The Commando head is basically just a 650SS head ( I have personal copies of the factory drawings of the 650SS, 750 Commando and Commando short stroke heads to prove it). The downdraught port design was introduced in order that, with straight inlet tracts, the carbs cleared the central oil tank used on the Domiracer not for any power gain!
 
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