Triumphrat

50yrDream · 03-05-2006, 05:20 PM

Back in the early days of my cycle enthusiast history-50's & 60's Triumph, BSA, Matchless, AJS to name some were always called Vertical twins(as opposed to the other kind of twin). I don't know when or by whom the phrase parallel twin came into being. Probably by some writer type similar to ones who called 40's cars Fat Fendered & 50's cars shoeboxes! To me a parallel twin is a Honda 600 scooter with the cylinders almost horizontal!
Not saying the new phrase is wrong or incorrect!! Just to me they will always be VERTICAL TWINS!!!
(Does that sound like an Old F**t spouting off or what!

Brooksie · 03-05-2006, 05:52 PM

Seems like the only design that is not a Vertical twin is the horizontal, or flat, twin utilized by BMW & Honda. V-Twins are higher than the cases, which may indicate vertical, technically. I almost forgot about the "parallel twin" monicker from my Honda 450 Hawk in '82. Great bike, great engine. Probably why I like the Bonneville since it provides such great midrange punch. Very streetable.

Diego · 03-05-2006, 09:04 PM

> (Does that sound like an Old F**t spouting off or what!

Well, yeah, but we just have to take these things into account. :-D

Actually, parallel twin is a perfectly good term to have available. It is different from both V-twins and opposed twins.

Vertical twins are also parallel twins!

But not all parallel twins are vertical; there are inclined parallel twins at all sorts of angles off vertical. Therefore, I tend to agree with you that we should continue to call the Triumph engines vertical twins.

dardoonk · 03-06-2006, 01:51 AM

Woudn't "parallel" indicate the cylinders are sitting adjacent to one another regardless of the acutal angle. Old Nortons, and even later when Triumph used them, the engines were parallel, but not vertical since they sat canted forward.

I suppose it would also be possible, but not likely, that an engine could be a vertical twin and the two cylinders not sit on the same axis in relationship to the crankshaft. Then you would have a non-parallel vertical twin.

RaceDweeb · 03-06-2006, 08:46 AM

I've recently seen a Chinese-built 800cc vertical twin cruiser. Up until recently, 250cc was the limit for these "mao-torcycles."

Diego · 03-06-2006, 02:34 PM

> Woudn't "parallel" indicate the cylinders are sitting adjacent to one another regardless of the actual angle.

Exactly my point. In practice, all vertical twins I've ever seen have been parallel. But not all parallel twins are vertical, since, as you noted, some of them are canted.

(I'm wondering which Triumphs you have in mind, though. I can't seem to think of any Triumph twins that used Norton-like engines.)

mecscc · 03-06-2006, 03:55 PM

All my old Trumpet twins were both parallel and vertical and I too don't remember any Triumph factory twins that were not vertical - but, bored as I am with cabin fever I will look it up in one of my Triumph history pictoral books and get out my trusty 90 degree draftsman tool and see if I can squander a couple of cold hours trying to figure it out! Which only proves that, call 'em whatever you wish, this thread reinforces the need to ride and get rid of this &^%%*&( weather lately!!!!

Got to go; they're coming to take me away................

Monte :-D

panda · 03-06-2006, 04:11 PM

Quote:

On 2006-03-05 19:04, Diego wrote:

Vertical twins are also parallel twins!

A parallel twin is where the pistons run together in paralell. i.e. they rise and fall together ( towards/away from the head) (nearly always firing at 360 degree intervals when four stroke) some vertical twins are not parallel twins, eg the honda 125 benly and other models (180 degree spacing of the pistons) also the triumph speedy ( 270 degree crank)

The flat twin bmw style boxer engine, can be considered a paralell twin from a timing (camshaft and ignition) point of view and delivers the same type of power. With both pistons moving towards heads together but the heads 180 degrees apart. this gives the same 360 degree firing interval as the paralell twin, although the layout is completely different. It has better balance as the piston movements tend to cancel each other out. Although with a small amount of rocking due to crankshaft offset of the two pistons.

Hope this clarifies things

dardoonk · 03-06-2006, 05:04 PM

Quote:

(I'm wondering which Triumphs you have in mind, though. I can't seem to think of any Triumph twins that used Norton-like engines.)

This is the one I was thinking of, actually a triple, I guess I can shut up now. :hammer:
1975 T-160

iandel · 03-06-2006, 05:17 PM

G'day,

Just to confuse matters, in the early 90's I had a Honda Zot. This was the first car that Honda made, circa '67. The reason I mention this is that it had a 2 cylinder, 360cc, engine where the pistons rose and fell vertically next to each other but the timing was 720 degrees.
Was this a parallel twin as well as a vertical twin?

See a picture here.

[ This message was edited by: iandel on 2006-03-06 15:22 ]