Downdraft .

Matt Spencer · Mar 1, 2022

The BREATHING may not really be the PROBLEM with the COMMANDO .

I can remember seeing stuff on someone doing a 8 Valve commando Head in the 80's.
Futile & a quicker way to blow the bottom end , I thought .
( Dean's racing commando had massive alloy radial cross braces , like Orange Segments - Going into bearing support plates . All welded . One I saw, anyway . )

WONDERING the IDEAL ALLOY for Commando Cases & Barrels ! . And the Ideal Steel for the Crankshaft .
Something like what the U S Navy used introduced in the late 60s for their Propellors , Pillow Bocks , and Propellor Shafts .- To cut resonance & Noise Signature .
If it was good enough for a ' Re Constructed ' P II to run 8's and smoke a slick past half strip , it must be pretty good . But the had Top Line engineers on the Development Project .
Now Thats what they call a ' Recreational Vehical ' .
The dealer was a bit confused at buy back time .
Presumeably this is Hobots mighty P II .

The project was way out over the way somewhere , classified . Mayberry type town closest . Same the photo & cross state anuall race report ( 8 or 9 entries , 1 bike ) .
father did sonic reading anylisis for a Commander , U S N , San Diago . Back maybe 68 . A queery to them re the fillm roll is unaswered . Maybe they'll get in touch ! .

Matt Spencer · Mar 1, 2022

" What would a 750cc Paton twin be like ? "

Those aussies Again ! ( Jim Eade M'cycles )

Of course , they all had trouble selling anything like this at the time . And making enough of them . of couse the TZ 750 screwed F-750 racing , for good then .
So any european factory investment was neglgated , and they all went to Endurance . till Honda steped in .

A Commando only needs mild reworking . It NEEDS Vastly Uprated Materials . And a 3 piece crank was out of date by 1960 at Triumph . a Iron Flywheel Might SHATTER too .

========================== PATON ? . ! looks like they stuffed up & made it UNIT construction .

o.h.c. & air cooled . theres some saying about HALF MEASURES . and not a lot wrong with PUSHROD High Cam O. H. V. whichll run well past 10.000 r.p.m. .

Quote Regarding TWIN CYL INJUNS .

" There's the electric high-speed machinegun method, and then there's the big cannon. This is the big cannon. A big engine doesn't have to work so hard to produce power, and it's usually simpler and lighter.' "

robs ss · Mar 2, 2022

Matt Spencer said:
" What would a 750cc Paton twin be like ? "

Those aussies Again ! ( Jim Eade M'cycles )

Of course , they all had trouble selling anything like this at the time . And making enough of them . of couse the TZ 750 screwed F-750 racing , for good then .
So any european factory investment was neglgated , and they all went to Endurance . till Honda steped in .

A Commando only needs mild reworking . It NEEDS Vastly Uprated Materials . And a 3 piece crank was out of date by 1960 at Triumph . a Iron Flywheel Might SHATTER too .

========================== PATON ? . ! looks like they stuffed up & made it UNIT construction .

o.h.c. & air cooled . theres some saying about HALF MEASURES . and not a lot wrong with PUSHROD High Cam O. H. V. whichll run well past 10.000 r.p.m. .

Quote Regarding TWIN CYL INJUNS .

" There's the electric high-speed machinegun method, and then there's the big cannon. This is the big cannon. A big engine doesn't have to work so hard to produce power, and it's usually simpler and lighter.' "

I was told an interesting story about those (downdraft) Laverdas.
You'll note how similar they are to the mid-size Hondas of that period.
Apparently when Laverda was trying to "crack" the US market, the US agent told them they needed a bigger engine and suggested they make a bigger version of one of "these" - and presented them with a current Honda (400cc?)
They did it and the big Laverda twin was born.
A bit more dishonest, if true, than Benelli, who apparently bought the drawings from Honda for the 500-4 in order to make the Sie. The similarity is just as striking as the Laverda above. Laverda seems to have made no attempt to disguise that likeness.

acotrel · Mar 2, 2022

Matt Spencer said:
The BREATHING may not really be the PROBLEM with the COMMANDO .

I can remember seeing stuff on someone doing a 8 Valve commando Head in the 80's.
Futile & a quicker way to blow the bottom end , I thought .
( Dean's racing commando had massive alloy radial cross braces , like Orange Segments - Going into bearing support plates . All welded . One I saw, anyway . )

WONDERING the IDEAL ALLOY for Commando Cases & Barrels ! . And the Ideal Steel for the Crankshaft .
Something like what the U S Navy used introduced in the late 60s for their Propellors , Pillow Bocks , and Propellor Shafts .- To cut resonance & Noise Signature .
If it was good enough for a ' Re Constructed ' P II to run 8's and smoke a slick past half strip , it must be pretty good . But the had Top Line engineers on the Development Project .
Now Thats what they call a ' Recreational Vehical ' .
The dealer was a bit confused at buy back time .
Presumeably this is Hobots mighty P II .

The project was way out over the way somewhere , classified . Mayberry type town closest . Same the photo & cross state anuall race report ( 8 or 9 entries , 1 bike ) .
father did sonic reading anylisis for a Commander , U S N , San Diago . Back maybe 68 . A queery to them re the fillm roll is unaswered . Maybe they'll get in touch ! .

Australian Comsteel 4130 is really strong shit. It could be used for making gun barrels if it was not so dirty.
It's composition is :
0,2 % carbon
3 % nickel
1 % chromium
0.6 % Manganese
0.2 % silicon
You need both the sulphur and phosphorus levels to be below 0,015 %

you can probably buy it from Bola Steel.

Un heat-treated, it has a tensile strength of 90 TSI

Matt Spencer · Mar 2, 2022

I think we'd better all chip in and build a decent Commando . And show these blokes wot they cando . Only problem , if a commities involved it'll be 60 Camel Power .

acotrel · Mar 2, 2022

Before I build my Seeley Norton Commando 850, it was a Seeley Laverda 750. I raced against it with my 500cc Triton. I blew it to the weeds, but the two into 1 exhaust system on it was too small at the collector outlet. When I was trying to but it, I could not get the Laverda motor, so it became a Norton. The Laverda motor is much heavier. I actually did the cam timing on it. It had an SFC camshaft which ran similar timings to a E3134 Triumph cam.
The Seeley Laverda was owned by one of my mates who sold it to another who pulled it apart to make it go quicker. The engine parts ended up in the hands of a car idiot
My mate who owned the Seeley Laverda, made a Seeley frame copy for a guy in NSW to use with a Laverda 750 motor.

These guys :

acotrel · Mar 2, 2022

In about 1973, Jim Eade brought a 750 SFC Laverda to Phillip Island. It was straight out of the crate and all that had been done to it was it had been put on methanol. The young kid riding it absolutely creamed all the fast Z900 Kawasakis.

acotrel · Mar 2, 2022

Laverda SFC replica experts...

Any of you knowledgable chaps know owt about Laverda 750 twins? Particularly the the SFCs and more particularly the do's / don'ts ... Good / bad... Etc regarding the building of a good SFC replica. Also any specialists or fonts of knowledge on the topic in the UK?

www.accessnorton.com

acotrel · Mar 3, 2022

If you were looking for a motor to copy and make larger to fit into a Commando the Suzuki Engine Auto Race ( AR600) might be good. They are DOHC and 4 valve per cylinder.

acotrel · Mar 3, 2022

robs ss · Mar 3, 2022

acotrel said:

Nothing to do with downdraft but... I liked it!

acotrel · Mar 5, 2022

I think it is impossible to buy an AR600 Suzuki engine, but there was a video on Youtube, showing somebody working on one of those motors - it looked excellent. One of those would fit into my Mk3 Seeley frame very nicely. The trouble is there would not be a race class for it. With four valves per cylinder downdraft is not so important

Matt Spencer · Mar 5, 2022

Was looking at them a while back .

Ran bars a bit like these on the Bonneville , pulled back M-X / ' western ' . Even a TWIN

These are a bit like EH Holdens . You dont see many around nowadays . No one can affford one anymore .

Downdraft .

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