Airfilters Commander

[Assen]

A question for Sir Richard; I'm planning to dispose of the airfilterhousings complete with the filters of my Commander and replace them with the K&N-type small airfilters. Do the carbs need adjusting when i do this you think? What are the pro's and con's you think? Many thanks in advance!!

[Richard Negus]

Hi Assen,No problems at all ! NML have done it on many customers' bikes and I have them on my own Commander; carb adjustments not necessary.Initially K&N's are more expensive but they can be cleaned and should last for ever.R.

[andygbsmith]

Is there any performance gains or is it just the long term saving on filters?Andy

[Richard Negus]

Hi Andy,The filters haven't been dyno-tested against the standard setup, but I don't think there is any improvement.Induction noise is increased as there is virtually no silencing - so it does make identifying a 'chuffing' engine more obvious.The main benefit is that you never have to buy another filter element.Secondary benefit is that the possibility of dust bypassing the element and getting into the engine is drastically reduced.R.

[Dell Boy]

Don`t know if it is common knowledge but the paper commander filters are Reliant Robin items available from your local parts store. Derek.

[Interpol2471]

Has anyone tried to convert an Interpol to use the same system of external filters as on the Commander, I guess it would make the engine run cooler with the better air flow?

[Richard Negus]

Converting air-cooleds to the same oil feed and rotor cooling air system as the Commander is a very good idea in theory. Fresh oil to the main bearings, air around the stationary gears - all good things !Doing it in practice is a different matter however ; City of London IP2's often cremated themselves after less than 1,000 miles of creeping along in City traffic.Both John Nelson and Doug Hele tried to achieve a longer life, but with limited success.Two of City's bikes were converted to 'reverse flow' which made a significant difference to engine life. Frank W (Real Classic) has one but I don't know where the other is. These two had rectangular holes in the lower face of the frame to connect to an adapter on the centre plate. Earlier versions had complicated induction plumbing to achieve the same result but at the expense of engine power. I don't know if any of these survive.Given that NML have a large stock of Commander centre plates, how about a reverse-flow aircooled engine with a watercooled centre plate, Commander transfer ports to support the engine, and a small radiator to keep it . No pump necessary - thermo-siphon should work. No frame mods, no complex plumbing. Seemples !R.

[Interpol2471]

Sounds like a good idea Richard but a bit expensive, I was hoping for an air filter and some tin plates

[Richard Negus]

I think the prototype P51's were reverse flow but can't recall how the engine was tied to the frame and how the air flow out of the centre plate was connected to the frame.They certainly had fabricated steel airboxes, with a foam element, above each end plate with the air inlet pipe above the radiator.Perhaps someone on here has saved some of those bits or remembers how the connections were made (Wust588 perhaps ??).The Commander was the first watercooled to have the centre plate extended up to the frame and cast aluminium transfer ports.For a one-off, it should be feasible to fabricate a duct to connect the standard air-cooled centre plate to the frame. To support the engine, it would need to tie in to the end plates as well since the centre plate only has two short M6 holes, not strong enough to support the engine.Paul, you could always try writing to Santa Claus .

[graham]

There's no reason why you shouldn't weld a Commander top on an interpol intermediate plate then use Commander air transfer ports. If anyone wants to have a go, I have the necessary expertise. Sounds like a worthwhile project. Air cooled engines need all the help they can get!I'm happy to make a reverse flow intermediate plate for air cooled rotarys exchange if there's a demand for it.Thinking about it though, you'd have to be a real enthusiast.... £300 to moly two faces plus labour etc total exchange cost including machining and welding with a pair of commander air transfer ports and O rings would be circa £500! That's more expensive than a trip to the Wankeltreffen so if you get your order in this week I'll be on the Hull ferry and away to Europoort ... I'll sort your intermediate plate when I get back.Grahamhttp://www.startright.co.uk

[Malc]

Am I right in thinking the Commander frame is reinforced around the area where the centre plate fits compared to the IP2 ?One of the other prototype reverse flow kits was loosely fastened to a red race bike mk2 version which i started to build many years ago and then dismantled to take less space. Needed to modify or fit 'water cooled' stationary gears to engine to suit. Engine got rebuilt as standard flow so as to be interchangeable with what I was using at the time.Malc

[Richard Negus]

Hi Malc,You're correct, the Commander frame has internal stiffening channels spot-welded along the front section (you can see them by looking in the round air transfer holes or a the carburettor inlet holes. No change to the frame externally in that area.The reverse-flow air-cooled conversions used standard stationary gears ; the l/h oil seal housing and r/h axial bearing housing had oil feed pipes brazed to them. The l/h one appeared between the fins and the r/h connected with a banjo to the obsolete oil scavenge position.As I'm sure you are aware, the Commander l/h end plate has its oil feed through the casting and needed a modified stationary gear to allow passage of the oil. For commonality, the modified gear was used on the r/h side although it was not necessary.The F1 feeds both gears through the castings and needs both stationary gears of the modified type.Rgds,R.

[graham]

Hi everybody, Another night with no rogue registrations and a fully functional website so I've time, to post a bit more 'pub talk' It's not difficult to modify a main bearing seal housing to take an oil feed to the flywheel side. I can take photos of one I have here if anyone's interested.The standard commander oil feed pipe and seal housing fits straight on to the drive side on original holes. The intermediate plate still needs modifying though...Anybody know why the Commander has extra plates in the frame? If it was to improve handling, it didn't work very well :-) Must goGraham

[Malc]

Hi everyoneI have an oil seal holder with the pipe brazes into it but seem to remember, although it is very many years ago now, one of the race mechanics said only to use water cooled staionary gears or modify the air cooled ones.Graham, apart from blanking off the intermediate plate oil feeds, what else would need modifying on this plate?Also, Richard, you mentioned that rotors were modded in various forms to try and stop smearing, are there any code numbers to identify any differences?Malc

[Richard Negus]

Anybody know why the Commander has extra plates in the frame? If it was to improve handling, it didn't work very well :-)

Hi Graham,The main reason for the plates was to increase torsional stiffness of the frame and improve straight line stability. Bob Rowley thought it was better, I believe. However, fitting Yamaha forks was a retrograde step in handling terms and probably nullified the increase in frame stiffness.A secondary benefit of the plates was to keep the side faces of the frame flat . I've seen new IP2 / Classic frames where the side faces are wavey where contraction after welding has pulled the sides in or out.R.

[Richard Negus]

I have an oil seal holder with the pipe brazes into it but seem to remember, although it is very many years ago now, one of the race mechanics said only to use water cooled staionary gears or modify the air cooled ones.Water cooled gears (part # 50-0771) are only needed with water-cooled engines ; the extra hole and slot in the w/c gear allows oil fed through the casting to get to the outer end of the main bearing. Also, Richard, you mentioned that rotors were modded in various forms to try and stop smearing, are there any code numbers to identify any differences?Malc

Norton rotors only had serial numbers for identification, and the early ones didn't even have that, and many have been modified along the way !There are really only three (?) different types of side faces :. completely flat side faces, early rotors. mainly flat faces with slight (.005") lower area around the pin seal holes, introduced by David Garside on the basis "if it can't touch, it can't smear". Didn't work. Mid-West style, where the majority of the side face is .005" lower than the area around the pin seal holes. Might have been better than no relief - but not proven.There are also three different types of rotor construction (look at the non-gear side) for fixing the bush to the casting :. three dowel pins used on early rotors ; pins occasionally come out and wreck the engine. three dowel pins + three M5 grub screws, all peened over to stop them coming out ; very occasionally come out, same result. three dowel pins, peened + three 6mm dowels radially through from the flanks, TIG-welded & dressed smooth ; much better very occasional failure, same result.The reason for failures is that the rotor casting runs hotter than its bush and differential expansion ensures that some movement & fretting occurs between the two.Even the current AIXRO-type rotors use a similar method of construction ; to the best of my knowledge, no-one yet has a one piece Norton-sized rotor in production and available.R.

[Bob]

Norton rotors only had serial numbers for identification, and the early ones didn't even have that, and many have been modified along the way !There are really only three (?) different types of side faces :. completely flat side faces, early rotors. mainly flat faces with slight (.005") lower area around the pin seal holes, introduced by David Garside on the basis "if it can't touch, it can't smear". Didn't work. Mid-West style, where the majority of the side face is .005" lower than the area around the pin seal holes. Might have been better than no relief - but not proven.There are also three different types of rotor construction (look at the non-gear side) for fixing the bush to the casting :. three dowel pins used on early rotors ; pins occasionally come out and wreck the engine. three dowel pins + three M5 grub screws, all peened over to stop them coming out ; very occasionally come out, same result. three dowel pins, peened + three 6mm dowels radially through from the flanks, TIG-welded & dressed smooth ; much better very occasional failure, same result.The reason for failures is that the rotor casting runs hotter than its bush and differential expansion ensures that some movement & fretting occurs between the two.At a later stage as we could not beat this fretting, induction hardened of the outer diameter of the Rotor bush nearest to the Gear was introduced, ensuring that the induction hardening did not migrate to the thins section by the gear undercut, this reduced the fretting damage. But did not cure the problem. Bob Even the current AIXRO-type rotors use a similar method of construction ; to the best of my knowledge, no-one yet has a one piece Norton-sized rotor in production and available.

[Richard Negus]

For those who perhaps aren't aware of the real identity of 'Bert / Bob', he's been a bit quiet since leaving 'old' Norton Motors, but probably knows more about the history and developments of rotary manufacture than anyone else. He also had a significant input into the JPS race team, even managing it in the period between Nick Collis and Barry Symmons.C'mon Bob, more contributions. Nice to hear from you again.R.

[Malc]

Thanks for the extra info on the rotors Richard, and also nice to hear from you again Bob. This is useful as I may try and get some blank rotors for the Mk 2 version of the red earlystocks bike. The RC588 rotors are pegged and tig welded and will stay in the original engine as I see no point in upping the compression ratio as it will only get limited use.The big Suzukis that now dominate the earlystocks are producing in the region of 125 bhp and I still feel that if I could get the right rider I would like to get the Norton competetive again, not to compete in the championship but just a few selected meetings. Rear shock top mounts must remain original and no frame bracing is allowed but different swinging arms and wider rear wheels are now allowed. Front wheels must remain 18inch.Something to aim for!Malc