Steering, brake fade

[RichardT10829]

Hey folks just looking for some suggestions regarding the braking and steering. When I am out and about the steering is perfect when I first start, but even after a few turns on the roads I am finding that the brakes are less and less effective, and by the time I get back home my brakes steering is negligible.


My linkages are all setup and I believe the clearance from the shoe to the drum is ok... With the brakes off I can step on the track below the sprocket and the drum turns without it binding.

My situation cannot be normal as the machines would be useless before even getting to the battlefield.... And they went on long runs !

[rob love]

Are the drums turned and clean of scoring? Full surface area is the key to preventing brake fade.

What is the contact area of the shoe's arc? Remove the drums and see what portion of the shoe is actually doing the work.

Are the shoes and drums clean? For this you must also remove the drums and inspect. The shoe linings and the drum surface area should be clean enough to eat off of. Any accumulation of grease will compromise the braking. making you have to apply the brakes harder and resulting in more brake fade. Potential sources of grease are the wheel seals and the brake adjusters, as well as grease added to the rub points between the shoe and the backing plate.

Are the drums round? You have to remove the track and axle shafts to test for that. Watch the fingers around those ice scrapers though if you are going to spin the drum around to test.

What are your driving habits? If you are constantly going past 90° then brake fade will be the result eventually. If you are dragging the brakes for long periods as opposed to a short hit, that may also be the problem.

Last, and this is kind of the wildcard: What are the composition of your linings. Since we don't have the luxery of the old school materials, the new stuff is not necessarily better.

Long story short, you will have to pull the drums to know for sure. Even though they may have been done not that long ago, you have the symptoms of a problem.

[RichardT10829]

Brand new woven linings oversized and profiled to match the drums which were cleaned up pristine on a lathe. No grease inside that I can see

[Richard Farrant]

Originally Posted by RichardT10829

Brand new woven linings oversized and profiled to match the drums which were cleaned up pristine on a lathe. No grease inside that I can see

Hi Richard,
Don't I recall that your shoe linings were a little too thick and you hand finished them with a sander or something? As Rob says, remove the drum now to see the face of the shoes to check how much contact area you have. Did you renew the hub oil seals?
Another problem with new type lining material is that it is not like asbestos where you could bed them in quick, this stuff will not bed in quickly and can glaze if you try to.

regards, Richard

[motto]

I hesitate to respond not being a carrier owner but as Rob suggested, perhaps driving technique has something to do with the problem or perhaps the way the vehicle is used with many turns over a relatively short distance. From what I know of drum brakes any of them will fade if worked too hard so dragging them is a no no and little jabs are preferable. At speed this must be done very carefully as the vehicle will spin out with little provocation.
Driving a U/C is not as easy as one might think. They can be quite treacherous, I know that much.
If the carrier has track displacement, (did they all have it?) is it fully operational and rigged correctly so as you are not relying entirely on the brakes? i.e.;brakes coming on too soon.
How hot are they when fade becomes apparent? They should function ok until they are damned hot.
Just some random thoughts as I am interested in the topic.

David

[RichardT10829]

I apply them with jabs rather than drags. I have noticed last night that when I go to take second the carrier stops (loses it's momentum immediately).... I must be just catching the shoes ? Which I am sure would make them heat up real quick. Also my foot pedal travel is very short before the brakes are applied. ( almost immediately) what sort of brake pedal travel should I have ?

[Rob Beale]

Hi Ritchie

Have you checked the adjustment of the brake linkages is as per the diagram in the manual?
Each of the bell cranks should be set so that they operate from just before right angled to just after, to get maximum leverage.
Try backing off the adjustment of the links to the actuators to give a bit more play and see if the drag when gear changing goes away.

Rob

[Richard Farrant]

Originally Posted by RichardT10829

I have noticed last night that when I go to take second the carrier stops (loses it's momentum immediately)....

Maybe brakes are dragging, did you set up the linkage as per the manual?

[RichardT10829]

Yeah as best I could without the little gauge tools. I have just re adjusted the shoe spacings by torquing them on at 80ft lbs then backed them off four flats... Cured the stopping issue. Took it on a run to the fuel station 1.5 miles up the road which consists of one left turn one right turn and a roundabout got home and a struggle to turn again.... Drums hot ! Again I am jabbing not dragging the brakes on. Going to pull te hubs now and have a look see.

[rob love]

There was a problem with the park brake creeping on during use in the carriers. But you would likely have noticed that by now.

The short jabs is the procedure I was alluding to as being best. When I was attached to an Infantry Battalian, we used to drive the M113A2s the short 200 km trip down the highway from Winnipeg to Shilo. If a driver tried to correct for road crown by merely holding back one tiller bar, you would end up with the overheat light going on for the controlled differential. The correct way was you oversteered slightly, and let the carrier correct itself until it just passed straight away, then you jabbed it again, and again, and again....... Man, the left arm sure got a work out over the 4 hour trip.

[rob love]

Originally Posted by RichardT10829

Yeah as best I could without the little gauge tools. I have just re adjusted the shoe spacings by torquing them on at 80ft lbs then backed them off four flats... Cured the stopping issue. Took it on a run to the fuel station 1.5 miles up the road which consists of one left turn one right turn and a roundabout got home and a struggle to turn again.... Drums hot ! Again I am jabbing not dragging the brakes on. Going to pull the hubs now and have a look see.

The tools are easy to make. Cut the basic shapes as shown in the manual. Use a digital caliper to mark the holes to their correct distance and center punch to mark the hole. Driill them out and weld in the appropriate size clevis pins.

I made my first set over 20 years ago, and was just using them a few weeks ago. Best bet is to make two sets. It will save you a couple climbs into the carrier and under the rear plate during set up.

[Lynn Eades]

Rich, make sure the bisectors (actuators) are free to "float" in their slots.
There should be a brass castle nut, split pin and washer on each stud. adjusted properly, this will let the whole brake assy.,find its own "centre" should there be any "out of round" in the drum, as it rotates. (hopefully there's none!)
How are you adjusting your wheel bearings?

[RichardT10829]

Done that Lynn. Pulled the drums and both clean as a whistle inside and from what I can see (images to follow) the shoes appear to be wearing over majority of the area. First image is of drivers side

[RichardT10829]

Gunners side

[RichardT10829]

Brakes engaged at 90deg with the extra as leverage onto the drum. I have very little travel on my foot brake before the brakes engage.

I thought maybe the brakes were coming on too close to the cam doing it's bit so to speak... Going to mull it over for a while and get some setting up tools made I reckon

[rob love]

Originally Posted by RichardT10829

Brakes engaged at 90deg with the extra as leverage onto the drum. I have very little travel on my foot brake before the brakes engage.

I thought maybe the brakes were coming on too close to the cam doing it's bit so to speak... Going to mull it over for a while and get some setting up tools made I reckon

The brakes are engaged or engaging at 90°? They should only start being engaged at just over 90°.

[Lynn Eades]

They look to have been bloody hot. Fair to say they have been dragging.
Give them a sand with some emery tape (following the curve) and then focus on getting the linkage adjustment sorted (as you said)
I cant remember how much turn of the wheel you have before the brakes start to act, but it's all in the books about how to set it up.
A comparison of the British and Canadian manuals helps with an overall understanding.
keep us posted.

[RichardT10829]

Cheers folks. Rob they are locked at 90deg. With your comment above I fear I have been dragging a shoe when simply applying the cam to steer .. I think a full re set of the linkages is order of the day... And clean up the shoes. !

[rob love]

Sounds like we may be onto the problem. When you set up the linkage distance (brakes torqued to 80 and the two fixtures set up at either end) the clevise at the steering box should just be engaging with the wheel at 90.

Remember that afterwards you will be backing the 4 notches, so once all is said and done, the actual locking of the brakes will occur well beyond the 90° point. At 90 to 95 degrees, they should just be starting to engage. Full lockup by the book is at 165°, although on my carrier it is a bit beyond that. It may be that my modern linings are still setting in.

From the Cdn manual:

During the 90° swing of the wheel no action should occur in brake linkage.....

[kevin powles]

Rich, Check your triangular floor mounted brake pivot plates in the drivers compartment, if the mounting holes are elongated / deformed or the plates are thin from corrosion they may be lifting off the floor when you apply the brake and not returning when the brake is not applied. This could also happen if you are using the incorrect pitched countersunk screws to hold them.

Also if your driver compartment floor is thin from corrosion it can warp when applying the brakes. if you suspect this as the floor on a carrier is only about 3mm plate when new you can put a strengthening bar between the outer most triangle brackets on the underside of the carrier.

You can get brake heat also if you are using the wrong kind of brake drum sealing strip material which is to tightly packed in.

let me know what you find after inspection.

kevin.

[RichardT10829]

Floor and mounts all good matey. I am not using any sealing strip so no issues there.

I have noticed that I have the linkage rods front to rear in the outer positions for worn shoes... May need to move them into the inner holes when I re adjust the thing.

Wouldn't care she drives like a champ, and everyone on the garage forecourt stopped and stared for ages as I fuelled her up "pay at the pump" I didn't even have to get out the carrier !

[kevin powles]

Rich, yes move the linkages, also get a sealing strip in there, keeps the water out, check the drain hole is clear on the back plate first.

Yes plenty of admirers I bet.

Kevin.

[chris vickery]

Richard
You put oversized linings on to make up for over spec drums correct?
My take on this is that your brakes are adjusted out too far causing drag and overheating of the drums to a point where you have brake fade as the shoes no longer contact the drum as it has grown in diameter.
Perhaps your drums are really too far out of spec or simply remove some excess brake lining

[motto]

The shoes will be in contact with the drum same as normal during fade. What causes the fade is a dramatic change in the coefficient of friction as the surface of the lining alters characteristics under extreme heat. That's why they have the burnt look about them. Contact area looks good.
I do believe you are onto the problem with the linkage/cam adjustment.

David

[Michael R.]

When Richie said his machine stopped on the 1st through 2nd gear change it made me think the brake shoes are not backed off sufficiently from the initial adjustment procedure. Although the good book instructs to back off the adjuster cone four clicks from the 80 lb torque used when setting up the linkage, you may find this is not sufficient to prevent excessive brake drag. You must adjust the number of turns in order to acquire the brake being full on when the steering wheel is rotated to 162-168. HOWEVER, see the bottom of page 71 in the AOP instructions.

Remember Richie is not using asbestos linings as called for in the original manuals. Some new ground being covered here. The drums should be able to turn by hand without binding, somewhere along the way there is a comment about slight drag.

The parking brake should be full on at four stops on the ratchet. That could give an indication of how much brake pedal movement can be expected.

Leaving the track off, you can check for drag once you have dialed out the four clicks. Using all caution to prevent your fingers being caught by the scraper or scraper bracket, turn the drum by hand. Have someone operate the steering and brake to see that the shoes are properly expanding while you turn each drum by hand, but also retracting when the steering or brake is released...

The issue of the shoes not retracting was partially addressed with the Windsor carrier steering, where the long rods are fitted in the forward compartment with strong coil style return springs.



Points that should not be dismissed:
The British manual and Canadian manual show different ways to adjust the steering linkage. I believe Lynn mentioned a benefit in reading both manuals.

plungers properly handed and lubricated. It is quite easy to miss this requirement, as they will assemble without any indication of error.
the ability of the actuator housings to float,
long rod clevis installed on inside hole Which is inconsistent with the AOP manual ...


A common fault on the Canadian Ross steering box is a worn rocker shaft pin creating end play. As the Ross gear does not allow for the pin to be replaced, not too many current owners are repairing damaged pins or fitting new rocker shafts. Wear on the pin can allow the wheel to rotate a considerable distance left and right before the worm/cam shaft is engaged.



Using the adjuster gauges was helpful for me. Very helpful.
.
.
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[Michael R.]

UC-F1 pages E1-E5

[Michael R.]

UC-F1 pages G1-G5 of six

[Michael R.]

UC-F1 page G6 plus four from the AOP manual

[Michael R.]

Aop 69-71 (+45)

[Michael R.]

From OM-I ... courtesy Stephen C.