Bradford wobbles

[beldavenport]

Hi can anyone advise why our Bradford Jowett wobbles sometimes after it goes over a large rut in the road. It is quite scary and feels like a wheel is coming off and to stop it we have to slow to a stop then set off again it is fine. We've checked the wheels etc and all seems OK.

[george garside]

assuming all is well in the steering department i.e. no play in kingpins, track rod ends, draglink and steering box it may be that the springs have settled so altering the castor angle (originally 2.5 deg.( camber angle ishould be 2 deg).

If all is in good order you could try fitting tapered wooden wedges under the front springs i.e. between axle & spring. taper should be 1/8 inch to zero with thick end to the front

george

[Keith Andrews]

I have often wondered why wood..
Iwould have thought wood will compress, rot whatever and eventually become loose...
Made of something like Aluminium would be better?

[george garside]

wood was the factory recommendation.- presumably decent hardwood but they didn't specify which. I have used wood with no probs deteriorating
george

[Keith Andrews]

wood was the factory recommendation.-

yeah have seen that for yrs

presumably decent hardwood but they didn't specify which

"Presumably" yes I have thought the same, even so it is not an area for presumption ....
Aluminium is what is and has been used for many decades in motor sport /hot rodding and in many countries specified by engineers.
I doubt if any certifing engineers or WoF inspector ...worth their salt would pass a wooden wedge.

Maybe this is something that should be cleared up.

The Wobble...many theories as to why, I read an articule in a NZ Flat four nor long ago....cant rem exactly how it when but talking about centrifical forces and when at a given angle or something the wheel wobbles like a coin wobbles as it spins roud in cicles.....It seemed to me it hit the nail right on the head.
A few of the NZ braddies have a (Think) VW hydrolic damper on the steering arm and by all accounts seems to work well.

[george garside]

the Bradford buff, the late Tony Turner of Colwyn Bay once told me that the steering of the Bradford improved noticeably if the engine was moved forward about an inch, thereby putting a bit more weight on the front aaxle. This came ab;out by chance as on CA & CB he found that the easiest way of fitting a pre war 4 speed box was to reverse the front engine mountings thereby saving shortening the propshaft.

george

[beldavenport]

Many thanks for all your suggestions. Everything is in order and the wooden frame was restored a few years back I believe. I am suspicious it is something to do with resonance like the bridge that carried on wobbling when the wind hit a certain resonance. It doesn't happen on every bump and only at certain speed not too fast not too slow. It hasn't happened very often but it each time it was a biggish bump in the road. Slowing to a stop then re-starting completely solves the problem. We've not had the vehicle long but it may be the way we are driving it. Despite the initial scare, we love our little Jowatt and are looking forward to going to a meeting in the near future

[george garside]

the symtons you describe are strong indicators of the need for wedge treatment as increasing the castor angle should prevent th;e increasing & uncontrolable oscillations of the wheels from side to side . This was a common problem amongst beam front axle cars & is not a Jowett peculiarity. The 'cure' was often covered in magazines such as 'proctical motorist'.

The fitting of a VW steering damper as mentioned by Keith can also be beneficial, the one to use is from a VW Beetle which should be readily availble from the numerous Beetle specialist suppliers. I did once try one on a CC with little gain as the steering/suspension was absolutely spot on anyway . I would also be a bit cautios about adding a damper as it may work by covering up a number of small 'faults' that can cumulatively add up to too much slop in the system, bearing in mind that the factory reccomendation was no more than half inch play at the steering wheel rim, a figure I always managed to achieve by means fair or foul!

George

[Keith Andrews]

The damper Im not convined is the answer...it is a very effect 'patch' fix in many cases.
Like George says "This was a common problem amongst beam front axle cars ..."
But not all models.....keeping in mind I have an American hot rodding background where bream front axle is common on T buckets, and American grafitti type cuopes....which where not prone ...
But they had the single left spring up front.
I am of the beleif it is a combination of factors, which one may eliminate even a couple but it will not eliminate the occurance.
Caster, The chamber at a given angle of turning, worn bushes, steering rods, steering box...how the steering box is mounted (which is crazy to say the least) Wheel balancing...and these set off the motion I mention was written about in a recent NZ flat four mag..(which I have miss placed.)

[george garside]

Keith makes an interesting point in that the dreaded 'wobble' does not usually occur on cars with a transverse leaf spring ( Ford, Austin 7 etc). Presumably this is because changes to the the 'set' of the transverse spring do not effect the castor angle which is presumablycontrlled by the radius rods. Wiath a semi eliptic spring on each side the caastor angle is more effected by the spring. altering with age.

george

[Keith Andrews]

Another thought ..Sry I was looking at this a few yrs back..having a few throughts
Large trucks can also suffer....which from chatting to a truck alingnment guy is fixed in adjusting the castor in the truck with huge hydrolic pressed across the axle during alignment....
Now apply that to a Bradford...wher do most ppl jack the front up from?
The center of the axle....put a straight edge along most braddy front axles and they are bent.. basically the same as the big trucks.... this is camber.
A wobble I have found it hitting a bump or pothole with the whhels just off center....not turning a very sharp cnr or striaght ahead....usually maybe advoiding a small pot hole and clipping it, or 2 constants I can do on purpose between home and the workshop..
going straight thru aroundabout that has a repair 1n the road.
The small speed hump driving into the workshop car park a fraction befoeree the whhels are fully straight.

Caster ...that alters the front to rear angle....like short forks or long forks on a motor bike...adjusts turning senistivity
Camber lean in or out...lean out the car 'falls over' lean in and grips in the cnrs....and the chamber varies as to the degree of the turn....
Then toe in...again works with caster and chamber so not to scuff tyres with the outside wheel trying to keep up with the inside wheel cicle diameter.

From what I understand ..Bradfords did not wobble from new..it was something that happened over time....which comes back to things like jacking upuinder the front axle.....sort of stuff.

[John Wolf]

I have experienced the same problem with my Bradford truck and it always occurred after I had greased the steering. It was almost as though a harmonic vibration was set up by a bump in the road. From experiance I found this could be stopped by bringing the vehicle to a complete halt, or swinging the steering wheel widley from lock to lock. (definately not recommended when other vehicles are around or when the wife is with you, as the reaction could be worse that the steering wobble)
The king pins, spring shackles, steering joints and steering box are all in good order. Wedges were fitted to the front axle but have since been removed as they did not solve the problem. For years I resisted fitting a steering damper but have now done so. This not only fixed the shimmy problem but also improved the tracking of the Braddie on the road by reducing the tendency for it to wander when the road surface was not good.
The steering damper fits nicely behind the front axle between the brake rod and tack rod and is anchored to a bracket fitted to the L/F U-bolt at one end, and an anchor plate attached two clamp brackets on the track rod at the other end. (may need to use a slightly longer U-bolt)
Care needs to be taken when installing the steering damper. The steering damper travel is the same as the total lock to lock travel of the track rod and any misalignment of the steering damper will reduce the steering lock of vehicle it is fitted to.

Details
Type of steering damper: - VW Combi Van. (the VW Beetle damper has two options with different types of end fittings but
can also be used)
Source: - Purchased from local VW specialist
Price: - Approx 70.00 NZ Dollars (approx 35.00 GBP)

[The Bradford man]

Dads old Bradford had a real nasty wheel wobbles in this one spot we would drive past outside the hosiptial.
He fitted combi steering damper and it never did it again.

[Mike Allfrey]

For what they may be worth, my comments on wheel shimmy with respect to beam type front axles on leaf springs.

My experience relates to an Australian International C1100 Utility (large pick-up). The company I worked for in the early 1970s purchased a C1100 for country field trips with farm machinery. The C1100 would all of a sudden start shimmy characteristics after a front or rear wheel struck uneven surfaces in the bitumen. Not uncommon on our roads. This, at times could become really violent and stopping the ute was the only way to get out of the condition.

We wore quite a track to the selling dealer and they went through all the motions - installing wedges as George describes here, new shackle pins and bushes, new steering joints and so on. We finally, once the warranty had expired, took it to a specialist truck (lorry) front end alignment workshop. After explaining our woes they removed the axle beam, stripped it bare and set it up on a surface table and checked all dimensions and angles they had on file.

They discovered that the castor angle was all over the place, set the beam up in a jigging fixture and, literally, twisted the beam outboard of the spring mount pads, to achieve the correct camber and castor angles.

From then on, that C1100 never shimmied again, until it was traded on a Chevrolet version of a Ford F100, whereupon awful steering returned. That Chevvy in some corners felt as if the two front wheels were not connected at all - just as frightening as violent front wheel shimmy.

I don't know if there is a jigging fixture anywhere that can accommodate a Bradford axle beam, but it could well be an interesting exercise.

Some try dampers in the steering linkage, VW for one, but I feel that is only fixing the symptom, not the actual cause.

Hope these comments help,

Mike A.

[Keith Andrews]

Large trucks can also suffer....which from chatting to a truck alingnment guy is fixed in adjusting the castor in the truck with huge hydrolic pressed across the axle during alignment....
Now apply that to a Bradford...wher do most ppl jack the front up from?
The center of the axle....put a straight edge along most braddy front axles and they are bent.. basically the same as the big trucks.... this is camber.

Which goes with my post above..
And where or who can do this?
Checkout truck wheel alignment specialists....
Have any of u seen a big Mac or volvo typr truck getting an alignment at your local tyres shop? No? thats why a specialist truck shop...
A panel shop with specialist chassis straghning macines can also do it..If they know how to use the equipment to its fullest potentual.