Anstey Shimmy

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simon.holyfield
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Anstey Shimmy

Postby simon.holyfield » Sun Jun 24, 2018 11:53 pm

Chaps,

As my SQ4 (1951 Mk1, Anstey frame) loosens up and I ride it more and more, I have realised there is a strange 'wobble' that occurs when I apply the rear brake, and when I release it again. It's the sort of shimmy that occurs if your wheel alignment is out, but it only occurs when the back brake is on - the bike tracks perfectly at all other times, and the suspension is adjusted properly, with minimal side clearance, and the chrome shackle bushes are like new.

Where should I look?
cheers

Simes

'51 Square Four,
'58 Huntmaster,
'42 W/NG,
'78 CX500
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Re: Anstey Shimmy

Postby nevhunter » Mon Jun 25, 2018 2:00 am

I reckon it's the torque reaction from brake application unevenly being applied to the drive/brake side. I'm not a great fan of the set up and only have ONE anstey framed bike which I don't have running at the moment, and I'm no hurry to get it on the road either. I don't wish to be part of a suggested fix if it involves changing anything from standard for" keeping my house" reasons.. There's often "funny" things happen when you put the rear brake on hard. Check tor play and free movement and make sure the tightening of the axle doesn't pull things somewhere they shouldn't be. Ie all lengths , Spacers nuts etc are correct dimensions. I also believe the axle should be quite tight to help both sides do the same thing when the suspension moves.. It's also undamped. Something more important on the heavier bikes, particularly with a pillion carried. Nev

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Re: Anstey Shimmy

Postby Leejm » Wed Jun 27, 2018 5:11 pm

I have my first Anstey ariel which I have rebuilt recently, I have heard they can be a little bit wayward on the road so if anyone has any hints or tips on these units it would be helpful to everyone.
1948 NH, BSA D10 SPORTS. 1953 VHA, 1951 KH rigid project.

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Re: Anstey Shimmy

Postby john.mitchell » Wed Jun 27, 2018 6:25 pm

In all the Anstey frames I have owned I have always fitted Sidecar rear springs. I always found solo springs felt slightly wayward
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Leejm
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Re: Anstey Shimmy

Postby Leejm » Wed Jun 27, 2018 6:28 pm

Cheers lucky enough mine came from the factory with side cars springs I reused from instead of looking for solo springs so looks I like I did the right thing.
1948 NH, BSA D10 SPORTS. 1953 VHA, 1951 KH rigid project.

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dave.owen
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Re: Anstey Shimmy

Postby dave.owen » Wed Jun 27, 2018 10:12 pm

After my solo springs went soft I fitted sidecar springs, 4 years and 15000 miles later they are also soft.

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simon.holyfield
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Re: Anstey Shimmy

Postby simon.holyfield » Thu Jun 28, 2018 12:04 am

But with sidecar springs, do you guys feel an increase in the 'waywardness' on braking?
cheers

Simes

'51 Square Four,
'58 Huntmaster,
'42 W/NG,
'78 CX500
http://ariel-square-four.blogspot.com

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Re: Anstey Shimmy

Postby david.anderson » Thu Jun 28, 2018 8:43 am

My 4 was initially fitted with sidecar plunger springs and I found that I may as well ride a rigid frame.
A few years ago there was an article in Cheval on the use of a period friction damper on the Anstey plunger. Dimensions were given in the article. I made a set and fitted standard springs and have enjoyed the ride and rear end control ever since. I have made damper sets for all my plunger frames. The damper uses steering damper friction washers and the star washer. I drilled and tapped the rear axle to fit one end of the damper and I made a new mudguard mounting stay stud to fix the other end. For bushes I used urethane trailer spring bushes. It only needs a little tension on the damper to correct the rear end.
David
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Re: Anstey Shimmy

Postby nevhunter » Thu Jun 28, 2018 9:09 am

Those dampers are similar to what was used on the front forks of Harley Davidsons on some of their race bikes, and are also similar to the Andre (French) articles. Good idea even more useful for the heavier Sq4 model than perhaps lighter models. Plunger rear ends like the Nortons and BSA's as far as I know are not damped. The earlier (pre war) Nortons had failures of the axle as it's subject to much more bending load than a rigid. I think a works rider was killed due to this . the Anstey design is different in that the clever movement keeps the chain more evenly tensioned and would have added considerable cost (and weight) to the more basic alternative. If there's much info on setting these up It would be perhaps a good idea to have it for constant reference to take the guesswork out of being close since new parts may be from unknown sources, and not necessarily perfect for the job.. The Royal Enfield Bullet of 1947 had a swinging arm which was well ahead of many other makes. So did the Moto Guzzi gambalungo sp? of about 1929 , quite early. Oh I forgot the Flying Merkel of 1912 and the 1913 Indian both with swing arm frames. Nev

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Re: Anstey Shimmy

Postby Leejm » Thu Jun 28, 2018 1:10 pm

So am I right in thinking there will always be some wayward movement on the rear due to the fact there is no dampening action on theses units without going to Davids method? The stronger springs help but then you lose some action?
1948 NH, BSA D10 SPORTS. 1953 VHA, 1951 KH rigid project.


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