"That hasn't happened before . . ."

pictures (or stories) of hideous injuries sustained by your ariel
will_curry
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"That hasn't happened before . . ."

Postby will_curry » Sat Sep 07, 2019 8:49 pm

I've owned and ridden Ariels for more than half a century now.

I've gone to work on them and down to the pub as well. I've trialled
then, solo and sidecar. I've grass-tracked them and hill-climbed them
with the VMCC. My wife and I have done the classic trials - Land's End and Edinburgh -
and this has never happened before. Not only has it happened once but I've
managed to have it happen twice, both times to the same bike.

I've had my Ariels, all except the one involved that is, for a very long time.
The exception is the HS which I've only had for a few years and haven't used that
hard up until recently. It was road registered and the price was right. I'd wanted
one of these for more years than I care to remember and I'd been collecting bits for
as long as well. It had lost the original mudguards and seat, the gearbox wouldn't
hold oil and the primary drive was full of water. The BTH TT mag was a distinct bonus.
I hadn't wanted a concours one. I wanted a real one - bent footrests and mud in the
end of the handlebars sort of thing and that's exactly what I got. One of those
rare deals where both the buyer and the seller went away happy.

Someone had spent some money on it and this included a pattern dual seat which
made getting the oil cap off and on nearly impossible. It has the early timing side
oil tank. I've got the drive side one waiting for the arrival of a drive side air
cleaner. Also in the list of new parts was a set of rear sprocket bolts and washers
and It's these that are part of the 'bad thing'.

I went on a 60 - odd mile run with the local section of the VMCC and at the end things
were beginning to feel not quite right with the final drive. Three sprocket bolts
missing and two on their way and the rest slack. Not good.

I replaced the missing bolts with originals from my collection, tightened up the
rest and thought no more about it.

hs_sprocket_1.jpg


Until the next outing, again with the VMCC and this time only 50 - odd miles.
The last 15 were done very gingerly and I arrived home with just 5 bolts left.
Something was obviously not right somewhere. The three origial bolts were still
there although somewhat slackened. The other two were removed, cleaned and inspected.

Where the originals have a plain shank which is a snug fit in the hole in the sprocket
the ones that came out had very little in the way of a shank and what there was wasn't
a particularly good fit in the hole. Needless to say the thread was somewhat undersize too.
The threads in the hub have suffered too but none are completely stripped.

A visit to Acme Stainless's website found a set of bolts and washers together with
nuts which must have been made for just this sort of disaster. A few days later a
package arrived. Inside quite the most impressive packaging I've seen were the nuts,
bolts and washers.

hs_sprocket_2.jpg


hs_sprocket_3.JPG


They fitted without any issues - even fitting the washers and nuts the other side
of the sprocket flange was easier than I expected.

hs_sprocket_4.JPG


There is another VMCC run coming up in a couple of weeks - third time lucky?

JohnnyBeckett
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Re: "That hasn't happened before . . ."

Postby JohnnyBeckett » Sat Sep 07, 2019 10:33 pm

HI Will i wold use shakeproof wsshers as well

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Re: "That hasn't happened before . . ."

Postby nevhunter » Sun Sep 08, 2019 5:46 am

The plain section of the new bolts is hopefully quite a neat fit in the holes in the sprocket.If your threads etc are worn I wouldn't be surprised if you continue to get problems.The back of the flange where you have put the "lock"nuts is an as cast surface and may need to be machined dead flat for best results. You could possibly do a fair job with a dremel and a flat stone if you are careful. At times I've had to spend a lot of time on these parts and I've actually chucked a few hubs rather than repair them if the brake surface was oversize also. Nev

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Re: "That hasn't happened before . . ."

Postby john.whiting » Sun Sep 08, 2019 6:56 am

As they are turned bolts,you could get Acme to make you some with oversize shanks ,and ream the holes in sprocket and wheel so the oversize bolts are a drive in fit......I would also "glue" together the sprocket and hub,and slop the bolts with loctite......My usual cure is to go to the next metric size,and ream the holes to a tight fit................i often see high powered twin cylinder bikes with the sprocket held on with only five or six bolts,and wonder if they will last.

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brenton.roy
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Re: "That hasn't happened before . . ."

Postby brenton.roy » Sun Sep 08, 2019 10:51 am

Is the chain stretched or the sprocket a little out of round?
'51,'56 Squares, '48 VH, '27 Model C, R67/2, Mk IV Le Mans, '06 Super Duke and Ariel projects.

JohnnyBeckett
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Re: "That hasn't happened before . . ."

Postby JohnnyBeckett » Sun Sep 08, 2019 2:48 pm

HI John modern motorcycles use a bigger size bolt and a lot stronger of about 10.2 ton braking to hold sprocket on and a good joining between the face of hub and sprocket to stop it moveing i have not had sprockets braking free just the chain and sprockets wearing a lot and the chain jumps off wen you give sum stick

will_curry
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Re: "That hasn't happened before . . ."

Postby will_curry » Sun Sep 08, 2019 4:48 pm

Gentlemen,

Thank you for your observations.

While a driving fit would be best the new bolts are a nice snug fit in the sprocket holes, probably
better than the Ariel originals I have and much better than the ones which failed. Even better from
an engineering point of view would be to 'dowel' the sprocket to the hub in the manner of a Vincent
clutch drum and this is always an option if and when my current repair fails.

While the threads in the sprocket flange are not wonderful they are at least good enough to allow
the new bolts to be tightened fully, something I wasn't expecting. The nuts on the spoke side of the
sprocket flange pulled up 'properly' so I don't think the flange is too far out of square/flat
and the nuts should fullfil their role of both support for the flange threads and as locknuts,
the reason for not using spring washers or loctite.

The chain does look a bit slack but that's due in part to the bike being on its stand
and wear, not because the sprocket is noticeably eccentric.

I shall keep an eye on the rear sprocket of this one hopefully to avoid things getting
into the state they did.

JohnnyBeckett
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Re: "That hasn't happened before . . ."

Postby JohnnyBeckett » Sun Sep 08, 2019 9:25 pm

HI Will i think you are on the right road with nuts and bolts i think the hub it bolt to is not thick enough from new i think it needs to be more then 1/4" thick to get a good fixing with just a bolt

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Re: "That hasn't happened before . . ."

Postby Mick D » Mon Sep 09, 2019 8:10 am

Hi Will

When you re-assemble the sprocket assembly make sure you take up any rotational play between the sprocket and hub in the direction of rotation, (rotate the sprocket in the DoR whilst holding the hub still), as you torque the sprocket bolts.

Regards Mick

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Re: "That hasn't happened before . . ."

Postby jj.palmer » Mon Sep 09, 2019 12:46 pm

One of the problems with bolts and locking nuts in this type of situation is that when the lock nut is tightened it may cancel out the tightening affects of the bolt. The lock nut is applying an opposing force to that of the bolt and may change the thread seating faces, therefore has the bolt stretches it may have different seating faces or none at all, I have tried to explain it better in the attached sketch.
Myself, I would try and adapt a method of locking by the use of lock washers, I have seen instances where a small hole has been drilled adjacent to the bolt hole in the sprocket, lock washers have then been made with a tang that fits into the small hole with the remaining part of the lock washer being bent to the bolt head hexagon.
Hope this helps if it fails again.

John P.
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