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What is scuttle shake and is there a cure?

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J

John_Progess

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I am about finished with all the welding on my 64 BJ8 PHI and I hear about scuttle shake. Does it occur on all Healeys and is there a reasonable cure. If I need to weld something to the chasis now would be the time. Thanks for your help and have a good day!

John
 
John,
From my experience scuttle shake is vibration that is generally felt at about 55-60 mph. There seems to be numerous causes that contribute to it.
1. Tires improperly balanced and/or out of round tires
2. rear brake drums out of round or balance, generally from the factory.
3. Drive shaft out of balance.
4. Chasis deterioration from rust.
5. Shocks in need of rebuilding or not tightened (nuts and bolts tend to work loose because of aluminum shock bodies)

In my case, I found that balancing the tires on the car rather than independently provided some help, although I still have some vibration. I have not had the rear drums or the driveline checked out.
There are several posts on this subject if you check the Forum's search feature.
 
Some people add some angle iron on the frame rails to the sheetmetal bulkhead at the transmission opening (maybe at the top corners too?).

I've pretty much eliminated it with the design of my rollbar's front (under dash) hoop; it's attached at the floor straddling the outriggers, at the top corners of the radius (and tied into the front suspension supports) and in the center at the heater duct. Nothing moves /bcforum/images/%%GRAEMLIN_URL%%/wink.gif
 
John,

Here is a tech article for the 'welding something' approach to 'fixing' the scuttle shake.

https://www.britishcarweek.org/scuttle.html

I was able to eliminate the shake on my BJ7 when I replaced tires/wheels/splines (but also had rebuild shocks and steering).

The factory made modifications to the tunnel opening at several times of production by increasing the number of spot welds and stiffening the opening when they went to the roll up window models (BJ7-8). According to Geofferey Healey's book, "The new and heavier screen (windshield) highlighted scuttle shake, a problem solved by Sid Enever by fitting a heavy guage diaphragm at the tunnel bulkhead junction."

Cheers,
John
 
Randy,
I would like to see a picture or drawing of the roll bar you mentioned. Under the dash support? Would you kindly let us see it?
Thanks,
Charlie
 
Coastalman said:
Randy,
I would like to see a picture or drawing of the roll bar you mentioned. Under the dash support? Would you kindly let us see it?
Thanks,
Charlie
Click to expand...
I'll show you what I can; please note that most of these pictures were primarily to highlight something other than the rollbar.

This barely shows the attachment in the heater channel (plate with bolts & holes); there's an angle iron bracket inside the duct that's bolted on two (2) planes.

MotoLita_101.jpg


The basic rollcage. The details of the rear hoop have been changed since this shot was taken (currently, the rear hoop is out so I could fit the soft top).

Healey_Rollcage.sized.jpg


Here, you can see how the front tubes are connected through the side panels, to terminate in the supports for the front suspension.

cai_003.jpg
 
Hi John

You asked "what is scuttle shake?".
Imagine driving down the road congratulating yourself on how absolutely well your recently-restored Healey is running. Then you hit 55 mph and out of nowhere the dashboard starts rattling and the steering wheel jumps about in your hand. It feels a bit like you're driving through an earthquake. Then as you hit say 60 mph it goes away completely, just as suddenly as it arrived. That's scuttle shake - as experienced by me in my '66 BJ8. The funny thing is, mine just started exhibiting this behavior a thousand miles or so ago. Dollars to Donuts mine is a wheel/tire issue.
Cheers
Randy '66 BJ8
 
Randy and John,

We had a similar issue in our 52 MGTD. We tried balancing wheels both on and off the car. Check wheels for out of round. Checked and rebuilt the shocks. Turned out to be a bad set of tires. The steel belts in the tires where the cause of the problem. New tires and the problem went away.

Hopefully I can keep the scuttle shake out of the 100/4 when it's completed.
 
I have spent considerable time reinforcing the outriggers and the rear frame extensions in the hopes to prevent frame sag after I have the door gaps done. I think I will try the angle iron reinforcing as mentioned above. Not that much trouble at this point. I have been cutting and welding on this thing for about a year so a little more won't matter especially if it helps. Have a good day!

John
 
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