Model 18 front forks

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Model 18 front forks

Postby Invicta » Fri Feb 08, 2019 10:56 pm

I am rebuilding the front forks of my basket case 1949 AJS model 18. I have discovered that they were fitted with sidecar 10" springs and the 3/4" and 1/4" spacers that fit either end of the springs. It clearly pulled a chair at some time as the frame coupling bolt was replaced with a longer one for sidecar attachment. I am aware from other threads on the site that the club spares scheme can supply 11" long springs part number 016526 and although it lists these for the later model forks and not for 1949 I believe that they are a direct replacement for part number 012972. My question is can anyone tell me what it would be like to ride a solo with sidecar springing in the front end. Will it make the ride too stiff and uncomfortable for a 13 stone rider. I can remember seeing some hefty double adult sidecars hitched to these 500 singles in the 1950's

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Re: Model 18 front forks

Postby Rob Harknett » Sat Feb 09, 2019 2:50 pm

If the sidecar springs are worn, new ordinary springs may feel stiffer If you look in 1954 master parts list, 016967 can be used in place of 012972 11" length. To notice any difference, you would need to ride a bike fitted with new types of different springs. Or you would not be able to tell any difference. Going the other way, use weak or ordinary springs with sidecar, you will feel something not right with handling. Riding solo, on rough roads may even prove better with sidecar springs.

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Re: Model 18 front forks

Postby Duncan » Sat Feb 09, 2019 4:04 pm

My 1957 twin had sidecar springs in it when I brought it, they gave a very noncompliant harsh ride, personally I would seek out some solo ones.

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Re: Model 18 front forks

Postby SPRIDDLER » Sat Feb 09, 2019 5:57 pm

Duncan wrote:..... personally I would seek out some solo ones.

Agreed. But I think Rob was suggesting that even solo forks with sidecar springs are better than his ride-to-work penny farthing. ;)
I poke badgers with spoons.

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Re: Model 18 front forks

Postby 56G80S » Sun Feb 10, 2019 8:05 pm

I kept the same springs in the 56 G80S that were on as the solo I rode up from Kent after I put the small wheel sidecar chassis and "coffin" wooden box on top.

It was my ride to work and North Yorks to London and I never noticed the difference.

Perhaps I'm not sufficiently "sympatico".

Johnny B

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Re: Model 18 front forks

Postby Invicta » Thu Feb 14, 2019 11:29 am

Thank you for the advice gents.
I have obtained a pair of springs from the club spares scheme part number 016526 but those sent are 13" long not 11" and have 29 coils, 9 more than my 10" springs. I have looked at photographs of springs from the British parts company in Austria that are described as 11" long and they too seem to have 29 coils. It seems I now have 3 choices, one put the original sidecar springs back in, two put the 13" long springs in that the club spares scheme sent , or three try to source some 11" springs elsewhere. Does anyone know how many coils the 11" springs should have? I think to use the 13" long springs it will be a very hard ride .

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Re: Model 18 front forks

Postby ajscomboman » Thu Feb 14, 2019 5:07 pm

Invicta wrote:Thank you for the advice gents.
I have obtained a pair of springs from the club spares scheme part number 016526 but those sent are 13" long not 11" and have 29 coils, 9 more than my 10" springs. I have looked at photographs of springs from the British parts company in Austria that are described as 11" long and they too seem to have 29 coils. It seems I now have 3 choices, one put the original sidecar springs back in, two put the 13" long springs in that the club spares scheme sent , or three try to source some 11" springs elsewhere. Does anyone know how many coils the 11" springs should have? I think to use the 13" long springs it will be a very hard ride .


The problem you're facing is that you are dealing with 2 different types of suspension here. What you have originally are shuttle valve forks and what you bought are springs for damper rod forks. The good news is, if you do indeed have shuttle valve forks and sidecar springs, stick with them and put them back in as the original solo spring set up was frighteningly horrendous in use. I have it on good authority from one who has experienced the shuttle valve forks. The ride was scary and total garbage. The sidecar springs are supposedly an improvement but still diabolical compared to damper rod type forks.

Return the springs and we'll give you a refund, but less the postage cost.

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Re: Model 18 front forks

Postby Invicta » Sat Feb 16, 2019 9:28 pm

Thank you for the advice. I do indeed have the shuttle valve type forks that were apparently only introduced for one or two seasons in 1949 before reverting to the damper rod type. so obviously they were not a success. I will re build them as you suggest. I have had the stanchions straightened and hard chromed and re ground and the plastic bushes replaced with the phosphor bronze bushes. I hope that the ride is not as bad as your informant claims. It is after all a 70 year old bike so I am not expecting it to ride like a modern machine..

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Re: Model 18 front forks

Postby clive » Sun Feb 17, 2019 12:22 am

Can't agree that the shuttle valve ride was so scary, did many a mile on them on my 49 G80. It is important however to know that when assembled from dry they need 10 fluid oz of heavy fork oil per leg not the usual 6 1/2 on the damper rod version (9 1/2 and 6 when refilling after draining as you don't get it all out). I did eventually convert it but only because the stanchions needed replacement and so I upgraded as the shuttle stanchions were not available. 30 odd years later I still haven't thrown the bent and corroded ones away!
clive
if it ain't broke don't fix

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Re: Model 18 front forks

Postby Invicta » Sun Feb 17, 2019 8:48 pm

Clive , Thank you for the reassurance that I will not be riding something like a demented pogo stick when I finally get the bike fully reassembled.
I have only seen conventional fork oil, which is quite thin. Can you tell me what 'heavy fork oil is and who makes it please.

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