Tank mounting, not for the faint hearted!

Information relating to the Matchless G2 or AJS Model 14 250cc Lightweight
good-hifi
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Tank mounting, not for the faint hearted!

Post by good-hifi »

Hi Steve, It seems fine now. Rubbers top and bottom, firmly fixed but with some movement to absorb enough vibration.

Cheers
Mick
RogerJ
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Tank mounting, not for the faint hearted!

Post by RogerJ »

But by using a metal sleeve that is shorter than the rubber, you squash the rubber and then tighten up against the sleeve. That way the rubber doesn't become over compressed.

Roger
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Biscuit
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Tank mounting, not for the faint hearted!

Post by Biscuit »

A clear and succint description Steve, it's pity that descriptions like this cannot be made 'sticky', still. I suppose there would be to many, what with rear wheels, clutch adjustment, primary chaincsae sealing etc.



good-hifi
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Tank mounting, not for the faint hearted!

Post by good-hifi »

I am still a bit confused...

If you have two washers with a sleeve between them and they are all tightened up firmly. How can any material around the sleeves, no matter how compliant, stop vibrations.

The vibrations will be transmitted from the frame into the metal washer touching the frame, along the metal sleeve, into the washer by the tank and then into the tank.

I really can't see how the rubbers can stop this since they do not form a sandwich with any of these components and it is only by forming a sandwich that they could work as a shock absorber.

Cheers



Mick
jim501
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Tank mounting, not for the faint hearted!

Post by jim501 »










Not common but I've seen these earth bonding strips on one or two bikes in the past. Don't know of any records of exploding bike tanks. Suspect it was just overkill because somebody spotted a theoretical risk. Putting the bike on it's stand earths the frame/discharges static but a lot of rubber tank mounting systems and plastic fuel pipes actually leave the tank electrically insulated from the frame.

Just brought it to mind because a friend of mine had a manufacturers recall on his Mondeo to fit an earthing strap on the fuel filler neck.

Somebody cleverer than me will know what becomes positive/negative. Me in me rubber soled shoes, the bike tank or the filler nozzle I'm holding.

cheers
jim
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paul knapp
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Tank mounting, not for the faint hearted!

Post by paul knapp »

G,day Mick, have a look at page 26 of this owners manual.. http://217.157.196.176:8181/ajs/Book/Ow ... Manual.pdf .. it is earlier than your bike, but it shows the sequence of the mounting parts.

....your tank does have threaded holes for mounting bolts.....doesn't it????..
...not large tubular holes, up in which an expanding rubber bung fits ????

Paul
___“As a hobby for the technically minded, motorcycling provides great scope.”

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good-hifi
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Tank mounting, not for the faint hearted!

Post by good-hifi »

Hi Paul.

Had a look at that, better book than the model 14 book that is for sure. This is what I've mounted mine like. The holes in my frame are rather oval and my tank does have threaded holes.

The 'restorer' got the wrong rubbers and the ones he fitted are like the one's in the diagram.

However I believe my bike should have four thin rubbers as there is not enough room for the tank to fit under the handlebars if the thick rubbers are used in between the frame and the tank.

I've not tightened the bolts up so that everything is rock hard. And the lockwire is to stop the bolts from unscrewing, nothing to do with an earthing system.

My personal opinion is that the sleeve is there to protect the rubber from the fixing bolts, not to act as a stop.

Like I said I cannot see how the rubbers could have any damping effect if there is metal to metal contact all the way from the frame to the tank.

Thanks for the reference, it is now saved to my PC.

Cheers

Mick
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paul knapp
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Tank mounting, not for the faint hearted!

Post by paul knapp »

Jim!!!..what are you on about??.quote: Not common but I've seen these earth bonding strips on one or two bikes in the past...you are not referring to the oblong shaped washer with a small hole drilled near one edge which is attached under the head of one tank bolt, are you?..On some earlier models this is used as the starting and finishing point to tie off a length of 22GA. copper wire which looped around beneath the tank, passing through the drilled head of the tank bolts, to "tie them" from unscrewing?..as described in the owners manual from my previous post.
Cheers, Paul
___“As a hobby for the technically minded, motorcycling provides great scope.”

J.B.Nicholson

Don't worry about the world coming to an end today. It's already tomorrow in Australia!


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paul knapp
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Tank mounting, not for the faint hearted!

Post by paul knapp »

Mick, the mount bolts MUST be pulled up firm, against a stop, otherwise the bolt threads will vibrate, ever so slightly, in the tank mount holes and eventually wear the buggers out!! Lawrence has posted about this problem before?? from memory!!
The sleeve OD. is smaller than frame mount hole, and must be positioned so it doesn't touch same before bolt is "nipped up". There is, or shouldn't be, any metal to metal contact between frame or tank or frame to tank mount bolts!
Pablo

................................
well it's midnight now an i'm gunna fill me 'ot water bottle an hit the hay!.....or wot ever?...
freezin' cold...'bout 8CEdited by - paul knapp on 26 Jul 2006 3:37:53 PM
___“As a hobby for the technically minded, motorcycling provides great scope.”

J.B.Nicholson

Don't worry about the world coming to an end today. It's already tomorrow in Australia!


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Steve Martin
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Tank mounting, not for the faint hearted!

Post by Steve Martin »

Mick, For a 'Sleeve Type' mounting, [ introduced in 1950/51] the 'correct' assembly for each fixing is as follows:

A. below the frame mounting...
one 5/16 x 26 bolt, [in my case 1.1/4" long]
one large ext. dia. metal washer. [1.1/8"]
one Thin, [3/16"] Rubber Washer.

B. above the mounting......ie. under the tank.....
one Thick, [5/8"] Rubber Washer.

C. The Sleeve, [13/16" or 7/8" long, I'm not taking them off again!] passes through both rubbers and the large hole in the frame bracket. It is unlikely that there will be any sigificant contact to transmit vibration between the frame and any metal parts of the fixing assembly attached to the tank. The sleeve is trapped between the tank and the top of the large washer, and , quoting from Haycraft 1953, 'the bolts can and must be fully tightened on assembly'

Only to be puckish you understand; I must point out that the bolts in the illustration are clearly shown to be drilled, and his final instructions are to 'Interlace the four tank bolts in pairs , using 22 gauge copper wire'! What did he know that we don't!

Even so Mick, the bolts should be tight, wired or not.

You say the tank sits too high with the thick rubbers, how thick are they? Itma has suggested a way to thin them down if necessary; but are you sure your handle bars are either the correct bend or adjusted properly. Some pattern bars are too long in the centre before they bend upwards; is this where it fouls the tank, or is it at the hand grip end of the bars? Most pictures seem to show bars with a reasonable rise, so as long as the bar clamp clears the tank, any clearance problems are more likely the result of inappropriate bars rather than tank height.

Both Jampot Spares and AMC Spares have what will probably be suitable replacement handlebars, and correct thickness rubbers; give them a call.

Cheers, Steve.
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