Annoying resonance

Anything about Ariels
bevanclark
Holder of a Nylon Anorak
Holder of a Nylon Anorak
Posts: 140
Joined: Fri Jun 08, 2018 3:58 am
Location: Methven, New Zealand
Contact:

Annoying resonance

Postby bevanclark » Tue Jul 09, 2019 1:16 am

Hi folks, my VB is geared up a bit and thumps along very happily solo at 50 mph, but if I go any faster (and when I throttle off at speed) there is an annoying lowish pitched resonance. It sounds as if it is coming from the front of the bike. The front guard is firmly fastened, but when I hit it from either side I hear a rattle which I assume is the fork springs. Is it likely that this is the source of the resonance ? If so, how can I eliminate it ? If not, any alternative suggestions welcomed.
Cheers, Bevan

charvey
Posts: 66
Joined: Sun Nov 04, 2012 10:10 am
Contact:

Re: Annoying resonance

Postby charvey » Tue Jul 09, 2019 9:35 am

Hi,
Is the bike girder or other type, girders wrap a elastic strap across springs if other type somebody will have a bright idea.

bevanclark
Holder of a Nylon Anorak
Holder of a Nylon Anorak
Posts: 140
Joined: Fri Jun 08, 2018 3:58 am
Location: Methven, New Zealand
Contact:

Re: Annoying resonance

Postby bevanclark » Tue Jul 09, 2019 9:50 am

Hi,
The bike is a 1950 plunger model with tele forks
Cheers, Bevan

User avatar
brenton.roy
Holder of a Golden Anorak
Holder of a Golden Anorak
Posts: 1993
Joined: Sun Feb 27, 2011 1:13 pm
Location: Adelaide, South Australia
Contact:

Re: Annoying resonance

Postby brenton.roy » Tue Jul 09, 2019 10:06 am

Hi Bevan,
What happens when you jack the front wheel off the ground, tie the brake lever on, grab the the bottom of the tyre and try to move it left/right (sideways) and backwards/forwards?
Are the wheel bearings, headstem bearings and fork bushes ok?
'51,'56 Squares, '48 VH, '27 Model C, R67/2, Mk IV Le Mans, '06 Super Duke and Ariel projects.

bevanclark
Holder of a Nylon Anorak
Holder of a Nylon Anorak
Posts: 140
Joined: Fri Jun 08, 2018 3:58 am
Location: Methven, New Zealand
Contact:

Re: Annoying resonance

Postby bevanclark » Tue Jul 09, 2019 10:56 am

Thanks for that suggestion, I'll check it out tomorrow. I should have added that the noise is rev related, not speed related, in that I can cause it to occur in 3rd gear as well; also downhill at speed on a closed throttle. I initially thought it was the tank vibrating against the headstock, since there is very little clearance, but I don't think it is that. Cheers, Bevan

johnwalsh
Holder of a Nylon Anorak
Holder of a Nylon Anorak
Posts: 277
Joined: Tue Dec 22, 2015 1:02 pm
Location: Burnham on Crouch Essex
Contact:

Re: Annoying resonance

Postby johnwalsh » Tue Jul 09, 2019 5:29 pm

I had an annoying eng speed related resonance on my AJS which turned out to be a loose fitting cover btn eng and g/box. When riding it sounded very much as thoughit came from the front wheel area. Is there any such cover on your bike ( I have no knowledge of your model). On the AMC models also, the fork stanchions have rubber sleeves to prevent the fork springs rattling.
1958 Huntmaster
1960 Matchless G12
1958 AJS 18s

bevanclark
Holder of a Nylon Anorak
Holder of a Nylon Anorak
Posts: 140
Joined: Fri Jun 08, 2018 3:58 am
Location: Methven, New Zealand
Contact:

Re: Annoying resonance

Postby bevanclark » Tue Jul 09, 2019 9:06 pm

Thanks John; I had also forgotten to say that you can ride through the resonance - it appears at about 52 mph and is gone by 60 mph. That would seem to be consistent with something rattling as you suggest. Was pondering it overnight and am not sure that the tank isn't the culprit - my Panther had a similar loud resonance that was in fact the tank. I resolved that by putting a length of closed cell foam insulation over the frame spine before fitting it. Will have a better look at the VB later this morning once it gets above zero in the garage ! Cheers, Bevan

nevhunter
Holder of a Golden Anorak
Holder of a Golden Anorak
Posts: 3674
Joined: Tue May 10, 2011 9:42 am
Location: Victoria.. Australia.
Contact:

Re: Annoying resonance

Postby nevhunter » Wed Jul 10, 2019 1:59 am

The fuel tank is the culprit in most cases. Set it up very carefully on the rubbers with no direct metal to metal contact anywhere. Nev

User avatar
brenton.roy
Holder of a Golden Anorak
Holder of a Golden Anorak
Posts: 1993
Joined: Sun Feb 27, 2011 1:13 pm
Location: Adelaide, South Australia
Contact:

Re: Annoying resonance

Postby brenton.roy » Wed Jul 10, 2019 10:01 am

Yes, could easily be the tank.
Anything out of balance could be the culprit, particularly if rev related. Luckily, there aren't that many rotating parts on a VB :D
As an example, I used a slightly loose crankshaft sprocket on a single. This spun unevenly enough to produce tight and loose spots in the primary chain. As the chain wear increased, the vibration amplified.
'51,'56 Squares, '48 VH, '27 Model C, R67/2, Mk IV Le Mans, '06 Super Duke and Ariel projects.

bevanclark
Holder of a Nylon Anorak
Holder of a Nylon Anorak
Posts: 140
Joined: Fri Jun 08, 2018 3:58 am
Location: Methven, New Zealand
Contact:

Re: Annoying resonance

Postby bevanclark » Thu Jul 11, 2019 12:30 am

Hi folks,
Just to finish this off:
- the culprit proved to be the mudguard. Although theoretically a 1950 bike, it has (according to Drags site) a 1951 guard with welded on centre stay pieces. Instead of 1/4 CEI studs and nuts holding it to the forks, the P.O. had fitted stainless bolts. One had come loose and there was a small fracture in the weld of the stay to the blade of the mudguard, allowing it to vibrate just a bit. Just been for a test ride after doing the necessary repair job and the annoying noise has vanished. Although I have no intention of flogging the old girl, I briefly wound her up to 60 mph and it sounds glorious :) (it has now got a 23 tooth engine sprocket).

- I am concerned about the tank and would be interested in seeing similar photos to the one attached - I wonder if I have an Indian made one, because with the rubbers fitted as specified, there is almost no clearance to the headstock. I can just get a very thin bit of rubber between the tank top and the bearing race. It is as if the tank mounting points are a couple of millimeters too far back. Also, there is considerably more clearance to the right of the headstock than to the left.

Doesn't seem like I can do much to move the tank back a little, other than "ovalling" the frame mounting bracket holes, which I am reluctant to do, for obvious reasons.

Would be interested in any further opinions.
Cheers,
Bevan
Attachments
Tank clearance.jpg


Return to “Ariel Talk”

Who is online

Users browsing this forum: MirkoCrkvenjakov and 14 guests