Scuttle Shake

[RAC68]

Hi Rich,

You presented the situation and solution very well. Many, including me, have misinterpreted rear drum imbalance, or even wheel imbalance/mistune, as scuttle shake based upon the vibration felt around the dash and commonly transmitted through the steering column/wheel. I have never noticed any deterioration or cracking around the transmission opening and, only in the last 15 years, did I ever hear of or consider that our drums were not balanced when manufactured.

So, thanks again for your contribution and all the best,
Ray (64BJ8P1)

 

[Griz]

There could be another explanation for scuttle shake. Resonant frequency. All structures have a resonant frequency at which point they will begin to vibrate, sometimes violently. Think Tacoma Narrows Bridge. As the wind blew across the bridge at a certain speed the bridge began to buck and literally disintegrated. While I agree that welding in angles around the transmission opening will not add much structural strength in the lateral direction, it may well change the inherent resonant frequency of the frame enough to reduce or eliminate scuttle shake at "normal" driving speeds. That being said, I will certainly have the rear brake drums balanced on my BJ7 which I'm presently restoring. I also have a Jule frame, and in talking to Martin, he claims that his frames do not suffer from scuttle shake. Since I bought this car as a work in progress and have never driven it, I hope Martin is correct! Griz

 

[John Turney]

When I went from front and rear drums ('57 BN 4) to front and rear discs and new wheels, all the shaking went away. Reinforcing the transmission opening tries to cure the symptom, but not the cause.

 

[Keith_M]

I've been watching this thread with interest. My Healey shakes a little at about 60mph, but nothing dramatic. I'm now wondering if this little bit of shake is due to the rear drums being out of balance. Does anyone know where one goes to get rear drums balanced? I've never heard of it before.

 

[Griz]

Keith, any machine shop that is set up to do engine balancing could probably do the work. Griz

 

[HealeyRick]

I was very pleased with Allen Hendrix's service: https://www.hendrixwirewheel.com/drums.html I found a heavy duty rubbermaid-style storage container worked great for shipping.

 

[CLEAH]

I completely understand and agree with the strategy to eliminate out of balance conditions on a Healey, and am willing to believe that in most conditions doing so keeps the scuttle from shaking, but that does not in fact cure scuttle shake. It removes the inputs that cause the scuttle to wobble. The scuttle shakes because it is inherently weak structurally. I don't know what kind of roads you guys drive on, but in these parts the roads are challenged, to be polite. Going over a frost heave at 30 mph will make the scuttle on a big Healey shake like a bowl of Jello. That's got nothing to do with out of balance wheels or brake drums. By comparison, my Sprite is solid as a rock going over those frost heaves because it is completely different structurally. So, I think both things are true: Eliminate sources of imbalance, and if possible, strengthen the structure.

 

[Keith_M]

Thanks for the info. I'll contact the machine shop that did my engine work and see what they say. If I strikeout there, it's good to know that Hendrix does it. It's too late for me to do anything about the structure, so I'll have a go at balancing everything I can.

I'm embarrassed to admit that I didn't balance my driveshaft before installing it. I think I'll pop it out and have it balanced as well.

 

[Keoke]

I was thinking about the possibility of bolting some bracing in place...
thanks

NO Steve bolting is not a viable fix for this problem it must be welded.

 

[BoyRacer]

I thought I would add one more thing to this thread. Back in the mid 1970's, when I acquired my first Healey, I learned that my Healey and many others suffered from scuttle shake. The cure was to take your Healey to an alignment shop that had one of those wheel balancers that would spin the wheels in place while still on the car. Since they have now long since disappeared, and many of our listers have probably never seen one...I will try to describe what they looked like. If you have ever seen one of those shoe polishers in the rest room of a posh hotel or restaurant, they look like one of those ...only on steroids. Once they had balanced your wheels, you had to make a mark on the wheel and hub when you later removed that wheel. If you did not, you would again have scuttle shake and you would have to re-balance your wheel.

It's odd...40 years years ago this was common knowledge. Today, so many people have alternative theories on what cases scuttle shake.

 

[Patrick67BJ8]

I thought I would add one more thing to this thread. Back in the mid 1970's, when I acquired my first Healey, I learned that my Healey and many others suffered from scuttle shake. The cure was to take your Healey to an alignment shop that had one of those wheel balancers that would spin the wheels in place while still on the car. Since they have now long since disappeared, and many of our listers have probably never seen one...I will try to describe what they looked like. If you have ever seen one of those shoe polishers in the rest room of a posh hotel or restaurant, they look like one of those ...only on steroids. Once they had balanced your wheels, you had to make a mark on the wheel and hub when you later removed that wheel. If you did not, you would again have scuttle shake and you would have to re-balance your wheel.

It's odd...40 years years ago this was common knowledge. Today, so many people have alternative theories on what cases scuttle shake.

I remember those balancers and they were billed as "the whole rotating mass is balanced and not just the wheel". You just had to remember to "mark" the lug nut and the hole on the wheel if you should ever have to take the wheel off. Not very easy to do on a wire wheel spline/hub. It was interesting to see the gadget that was installed to balance the wheel as those round shaking rollers were "dialed in to "smooth" and they did work very well to balance the whole wheel, tire & brake drum, etc.

 

[Keith_M]

I thought I would add one more thing to this thread. Back in the mid 1970's, when I acquired my first Healey, I learned that my Healey and many others suffered from scuttle shake. The cure was to take your Healey to an alignment shop that had one of those wheel balancers that would spin the wheels in place while still on the car. Since they have now long since disappeared, and many of our listers have probably never seen one...I will try to describe what they looked like. If you have ever seen one of those shoe polishers in the rest room of a posh hotel or restaurant, they look like one of those ...only on steroids. Once they had balanced your wheels, you had to make a mark on the wheel and hub when you later removed that wheel. If you did not, you would again have scuttle shake and you would have to re-balance your wheel.

It's odd...40 years years ago this was common knowledge. Today, so many people have alternative theories on what cases scuttle shake.

I also vaguely remember these balancers, and it seems like a better approach to me. Sorta like balancing your crank, flywheel, and clutch at the same time. I wonder if it went out of use because it is unnecessary (i.e., brake drums etc on modern cars are better balanced than older cars) or for some other reason?

 

[CLEAH]

On-car wheel balancing is still done, and the equipment is still made. The trick would be finding a shop that has that capability, as your typical Firestone shop probably does not. What has certainly changed over the years is cars have gotten much better (obviously) such that less-than-perfect balancing is a non-issue, and at worst shows up as a vibration in the car or steering--it does not shake the car apart. People have tried for years to find ways to improve the scuttle on big Healeys--because while you can dial in the balance of the rotating bits, you can't always have the luxury of driving on billiard-table smooth roads. I'm fine with being told it is an engineering impossibility, but Geoff Healey reported that the craftsmanship at Jensen was suspect, and that their skimping on welds "did reduce the rigidity of the body somewhat." So, why not run a bead of weld around the doghouse, or maybe add some angle iron--in addition to making sure the round things are well balanced? Seems reasonable.

The quote is from Jon Pressnell's book Austin Healey: The Bulldog Breed

 

[CLEAH]

So here is a question for people experienced with BJ8s and pre-BJ8s: Are BJ8s more prone to scuttle shake than their older brethren? I ask because there is an important difference between the two, and that is the dash. Early cars have the one piece steel dash, and BJ8s have the multi-piece affairs. One is rigid, and the other most decidedly is not.

Imagine that the entire bulkhead assembly is a cardboard carton, with one end open, tipped on its side. The closed end of the carton (the firewall) is reasonable stiff because it is boxed in. The open end (the cockpit side) is open and will wobble with a force applied to it. To stop it wobbling, pull out one of the flaps and tape it, partially boxing it in. You've just made it much stiffer.

When they designed out the metal dash, did they take away a fairly significant piece of the structure (the flap in my example)? Not to mention the loss of the parcel shelf as well.

 

[Bob McElwee]

Years ago when we drove the 67 BJ8 to Florida (by way of Ohio) a spoke broke as we left Ohio. I used that as the leverage to convince SWMBO that we needed to get new wheels and tires. When we got to my parents in Sarasota. I ordered 4 new 72 stainless steel spoke wheels from British Wire Wheel and had them delivered to my parents home. When they arrived I took them to a local Goodyear dealer and had 195/70 X 15 tires mounted. the young man mounting them rolled out a on-wheel balancer and started balancing. He asked me to put my hand on the fender of the wheel being balanced and hold my finger out. It was fasinating as he adjusted the dials and put weights on and moved them. When he was finished I could feel no vibrations. Before the new wheels and tires we had a slight shake around 55 MPH and afterwards smooth as silk. I put a mark on the front hubs and back brake drum to indicate where the air valve was in order to remount the wheels in the correct position.
When we got our 62 BT7, it also had a slight shake 55 - 60 MPH. After putting the mini-lite look a likes on the shake has gone away to never return through several sets of tires which have been balanced on the current variety of off car balancers (by someone who know how to work with knock off wheels).
I think the scuttle shake is common to all the 6 - cylinder Healeys, don't know about the 100's.

 

[John Turney]

So here is a question for people experienced with BJ8s and pre-BJ8s: Are BJ8s more prone to scuttle shake than their older brethren? I ask because there is an important difference between the two, and that is the dash. Early cars have the one piece steel dash, and BJ8s have the multi-piece affairs. One is rigid, and the other most decidedly is not.

Imagine that the entire bulkhead assembly is a cardboard carton, with one end open, tipped on its side. The closed end of the carton (the firewall) is reasonable stiff because it is boxed in. The open end (the cockpit side) is open and will wobble with a force applied to it. To stop it wobbling, pull out one of the flaps and tape it, partially boxing it in. You've just made it much stiffer.

When they designed out the metal dash, did they take away a fairly significant piece of the structure (the flap in my example)? Not to mention the loss of the parcel shelf as well.

Although my BN4 has the one-piece dash, it's held in place by not many bolts, I think no more that 5. The panel around the transmission opening is somewhat different on 100-6 and early 3000s than on later cars.

 

[Keoke]

I remember those balancers and they were billed as "the whole rotating mass is balanced and not just the wheel". You just had to remember to "mark" the lug nut and the hole on the wheel if you should ever have to take the wheel off. Not very easy to do on a wire wheel spline/hub. It was interesting to see the gadget that was installed to balance the wheel as those round shaking rollers were "dialed in to "smooth" and they did work very well to balance the whole wheel, tire & brake drum, etc.

Patrick it was easy to: Put a mark on the front hubs and back brake drum to indicate where the air valve was in order to remount the wheels in the correct position-----:wink-new:

 

[SteveHall64Healey]

I thought I would add one more thing to this thread. Back in the mid 1970's, when I acquired my first Healey, I learned that my Healey and many others suffered from scuttle shake. The cure was to take your Healey to an alignment shop that had one of those wheel balancers that would spin the wheels in place while still on the car. Since they have now long since disappeared, and many of our listers have probably never seen one...I will try to describe what they looked like. If you have ever seen one of those shoe polishers in the rest room of a posh hotel or restaurant, they look like one of those ...only on steroids. Once they had balanced your wheels, you had to make a mark on the wheel and hub when you later removed that wheel. If you did not, you would again have scuttle shake and you would have to re-balance your wheel.

It's odd...40 years years ago this was common knowledge. Today, so many people have alternative theories on what cases scuttle shake.

Hey Richard, I had this done as the first step in this journey, and they used equipment just as you've described. It cut the problem in half, but did not eliminate it.
Steve

 

[Patrick67BJ8]

Patrick it was easy to: Put a mark on the front hubs and back brake drum to indicate where the air valve was in order to remount the wheels in the correct position-----:wink-new:

Why didn't I think of that when I was young and knew eveything??

 

[ttrotter]

I can't find where anyone has mentioned the "harmonic balancer" as a potential cause of the shake. After repairing wheel spokes, truing the wheels for runout, balancing the tires properly, and balancing the rear drums, if the car still has scuttle shake my next step would be to replace the harmonic balancer.
Just a thought.
Tom