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Tankslappers


madoc
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I just stripped my m62 to its components, had it blasted, zinc'ed and powdercoated and then reassembled using as much stainless as poss.

 

 

 

I took it for MOT test today and it has God almighty Tankslappers at around 20mph.

I made no adjustments to the chair geometry, while in pieces, and it still tracks true at speed anyway. I did replace all the wheel bearings and head bearings and they are all tight.

 

I fitted a leading link front end a year back and it was fine then, as it was before the strip and rebuild.

 

Bit mystified as to why I am getting these severe oscillations in the bars ?

the damper is damping but doesn't seem to control them much ...

 

Ten years with this ural now .. First for me ... And it's been run around with shagged bearings, tyres and all sorts in the past ...post-1234-0-10196700-1452123657_thumb.jpg

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well ...

 

I have checked the damper and roughed up the friction material.

The head bearings had a trace of play, which is now removed.

I cannot find any play in the front end or elsewhere ...

 

The only thing I can think of, is that the sidecar swingarm had a seized bolt (when I took it apart) which may well have prevented any flex in the sidecar suspension. I had to hacksaw it through to get it off and then smash it out and get another bush.. By that stage of dismantling, everything was in pieces anyway and I couldn't be certain as to impact.

I could have set it up, in the dim and distant past, with this situation in place.

 

I didn't think I disturbed any of the sidecar settings at all, with everything apart.

 

As I am a RH chair in a "drive on the left-hand side country" then I think I set my bike to sit upright (rather than with lean out).

Is a minor change going to really produce the death wobble I have ? Believe me it is pretty bad ...

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The tread profile of the front tire can cause tank slapping, too.

Flat tread will do this as it causes the tire to "skip" back and forth from one contact side to the other. A good round profile prevents this.

Although your photo seems to show good profile on the front tire.

 

I have seen this problem occur on several rigs. A new front tire solved the problem.

Just a thought.

~RN

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thanks

I had some workshop time last night and checked all three wheels.

I select that with the least wear and least run-out (russian wheels eh ?) and swapped it in.

 

I then removed the two upper sidecar to bike bars (and cured the oil leak from the sidecar side rocker cover).

Turns out they are both rusted solid, so they couldn't have moved during re-assembly.

Next workshop session will see me free them up and check the lean-in.

 

The adjustment joint for the toe-in has also not moved, as expected.

 

I am mystified.

I have had the chair off numerous times in the last 10 years with no issues on re-assembly. Even the leading links created no wobble on initial installation a year ago.

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IMHO a leading link. with an out of round tire and wheel will induce wheel oscillation quicker than any other condition, I concur with Mr Noe.....Ken

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Update.

A few things, which I think have sorted it.

 

I found the bolt holding the rear "tulips" to balljoint loose

I swapped the wheels around for the best balance and tyre

The front wheel was out of alignment to the rear BUT it must have always been like that ... Something is odd, but I utilise some spacers to correct it back to align with rear.

The toe in was a few mm under, so I adjusted it for a few mm more.

 

I need to run a bit further and faster than just up and down the road to be certain.

Thanks for all the support !!

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