FF57 and its bigger brother

[Tom Gaynor]

The first problem I had with FF57, about six years ago, was that there are two variants, short and long. Since none of the literature I had gives dimensions, then how does one know if what one has is short or long? Unerringly I seem to have bought and fitted the wrong ones.
Jacqueline Bickerstaff however, whose book I've just bought, does give dimensions: mine should have short, 5/8", ones (FF57). I was quite certain (icy chill grips the heart - you get the picture) that what it must have had for six years were long ones (1"). And so it turned out to be. Aaaaarrgh!! And I have a Thornton damper, not an Armstrong one.
But the sky has NOT fallen, despite warnings of imminent disaster.
I haven't ridden the bike since I changed over to short ones (too damn cold...) - but it'll be interesting to find out if it makes any noticeable difference.
And the answer to the question she asks on page 122? Black steel mudguards were a factory fitment on at least half-a-dozen bikes , dating mostly to 1951. Mine is one of them, and there is no room for doubt.

 

[davidd]

Tom,

I ordered the wrong ones many years ago, but I had a "D" and I realized that they were the wrong ones to fit to the Thorntons. I was annoyed at John Healy for sending out "D" items when I had clearly ordered using the "C" parts list supplied by Harpers which lists FF57/1 only. Of course, this is the "D" item and although the drawing is correct, the description section is not. FF57 is the short one.

I would be interested in your comments on the difference, but I suspect there will be nothing noticable. As far as I can tell it just extends the front end a little more, which is not helpful from a handling point of view, but it seems not to have put you in much peril. I suspect the "D" items were designed simply to make up for the slightly shorter stroke of the Armstrong damper which became standard with "D's".

David

 

[timetraveller]

To check what might have happened all one has to do is to place a jack or other lifting device under the front stand and lift the bike up enough so that the front wheel is totally off the ground. Now move the handlebars and see just how close the rear of the mudguard and lower stay is to the front of the mag cowl. If you still have clearance than all is well. However, you might find that the mudguard and/or stay fouls the front of the mag cowl. If it does then imagine going round a corner and hitting a humongous pothole so that the front forks are fully extended. It could get interesting!!

 

[Hugo Myatt]

Just a point. Not all Armstrong dampers have the same extended length. Some need the short FF57s.

 

[Tom Gaynor]

As recounted several times, I've experienced three tank-slappers (none Vincent) and "am difficult" to persuade that they can be "managed". Accordingly I fitted an hydraulic steering damper when building the bicycle, thus making tank-slappers things i didn't have to think about. It remains the best single reason for fitting one: £50 for peace of mind - a bargain! So while fitted with FF57/2 it has never given me any cause for alarm, I'm covered anyway.
As timetraveller (Norman: something more concise? I'm measurably older by the time I've typed your n-d-p....) has said, there isn't much clearance between guard and cowl, but since the bike sits on its centre stand "topped", which is the worst case, and the wheel moves FORWARD on initial deflection, I've seen no signs of involuntary intimacy.
It is scarcely fair, but having raced a Petty Norton, it's difficult not to judge everything by that. The Vincent feels "remote" by comparison, as though the front MIGHT be about to let go, or might not. With the Petty, I KNEW. I suspect however that this has a lot to do with tyres, and that a 20 x 3.00 just doesn't have a big enough footprint. And while it is as sticky as race tyres were 30 years ago, it is nowhere near as sticky as modern race rubber. I raced a 350 Manx, which had a 3.50 x 19 Speedmaster front, and a 4.10 x 19 Avon GP rear, both in race compound, and it was fantastic. I actually managed to get among the Hondas. But at the end of the weekend the front was slick on one side, with the last three ribs completely worn off.
Too cold today for Vincents, so no comparison yet. Today I rode the Sunbeam S7 45 miles, the only other post-war fully engineered design. (Everything else, from BSA, AMC et al, was a parts-bin special that could have been built in any back street garage. Discuss...)
I don't so much ride it as "drone" it, at a serene 60 mph. Interesting that on a steady throttle it has very good steering through the twisties: the problems come when the throttle is closed, and torque reaction leans the bike to the left. Opening it leans it to the right. Makes right-handers interesting... And reminds me of the joke about Georg Meier(?) in the '39 TT on the blower BMW. When he took off over Ballaugh Bridge the motor stopped and the bike revolved...

Tom,

I ordered the wrong ones many years ago, but I had a "D" and I realized that they were the wrong ones to fit to the Thorntons. I was annoyed at John Healy for sending out "D" items when I had clearly ordered using the "C" parts list supplied by Harpers which lists FF57/1 only. Of course, this is the "D" item and although the drawing is correct, the description section is not. FF57 is the short one.

I would be interested in your comments on the difference, but I suspect there will be nothing noticable. As far as I can tell it just extends the front end a little more, which is not helpful from a handling point of view, but it seems not to have put you in much peril. I suspect the "D" items were designed simply to make up for the slightly shorter stroke of the Armstrong damper which became standard with "D's".

David

 

[timetraveller]

Tom, to avoid repetitive strain injury I will not be offended if my handle is abbreviated to 'tt'. Just keep your fingers away from the letter 'i'!! The bike being on the centre stand will not check the clearance unless someone sits on the back so that the front wheel is well into the air. I helped a local chap with a racing twin a few years back which had the wrong combination of FF57s and damper. The mudguard and stay actually interfered with the front of the engine for about 20 degrees each side of the centre position. If anyone is unsure, it is not when the forks are fully up that the problem occurs but when they are fully down.

 

[Tom Gaynor]

I take your point, but mine does sit pretty well topped out, and there's about 1/4" clearance worst case. When I jacked it up under the engine to swap FF57/2's for FF57's, it scarcely lifted. (And what a bloody awful job it was, in a temperature just over freezing!)
I had the opportunity again to use a Spanish windlass (orange binder twine, doubled) to take one front spring off, and while I wouldn't recommend this operation to anyone "of a nervous disposition", the top bolt, once slackened, came out by hand. And, job done, it went straight back in again, again by hand, and I didn't punch a hole through the tank because the windlass had slipped. Easy peasy. It is important to use more binder twine to secure it so that it can not slip before cranking the handle up.

Tom, to avoid repetitive strain injury I will not be offended if my handle is abbreviated to 'tt'. Just keep your fingers away from the letter 'i'!! The bike being on the centre stand will not check the clearance unless someone sits on the back so that the front wheel is well into the air. I helped a local chap with a racing twin a few years back which had the wrong combination of FF57s and damper. The mudguard and stay actually interfered with the front of the engine for about 20 degrees each side of the centre position. If anyone is unsure, it is not when the forks are fully up that the problem occurs but when they are fully down.