Jump to content

Handbrake compensator - what does it do ?


Recommended Posts

I'm just getting into the rear suspension and axle of my TR3 and with all of the **** removed I can now see the assembly that actuates the handbrake via the cables to the rear wheel cylinders.

 

The manual calls this a "compensator bar" and I wonder what it is compensating for ?. I get that it provides a pivot for the three legged gizmo that the cables attach to and I see why it needs felt seals as the gizmo seems to have a grease fitting at each end.

 

Is this thing supposed to provide adjustment or is the goal only to allow it to rotate about the two axis ?

 

Stan

Link to post
Share on other sites

Stan, it's just a simple device to even up shoe pressure on the drum side to side.

 

Works well too as a properly adjusted handbrake will lock up the rear wheels.

 

Viv.

 

 

Ha !. too bad they didnt keep that design through the TR6 !

 

Thanks Viv. Is the installation as simple as screw the parts together so that they are snug but still freely rotate ?

 

Stan

Link to post
Share on other sites

Ha !. too bad they didnt keep that design through the TR6 !

 

Thanks Viv. Is the installation as simple as screw the parts together so that they are snug but still freely rotate ?

 

Stan

 

Clean all the old grease out and then fit new felt seals and grease the threads, then screw it in until it is tight and then just back it off until it is in the correct upwards orientation. Grease through the nipple when assembled just enough to see it appear around the seals..

Stuart.

Link to post
Share on other sites

First, push hard on the footbrake to centre the shoes, then adjust the position of the shoes within the drum, a quarter turn at a time, until the brake is just binding, then back-off a quarter turn and check that the drum rotates freely. If necessary, press hard on the footbrake and repeat the adjustment. Repeat process for the other rear wheel.

Then adjust cable lengths so that the compensator's vertical arm remains more or less vertical as the handbrake is applied, and the movement on the handbrake lever is minimised - don't overdo it as you may start to apply the brakes!

 

This simple and effective system cannot be applied to TRs with wobbly rear wheels (a.k.a. IRS) as the distance between the back plates varies depending upon load, road surface etc. If such a system were used, the rear brakes could be released if the load in the car changed (driver/passenger/luggage in or out of car) - not a good idea! Be glad that you have a simple beast which has a handbrake which works very well, suspension mountings which don't fall off, a drain plug in the rear axle - all these benefits were removed by the 'improvements' incorporated later!

 

Ian Cornish

Link to post
Share on other sites

Stan - I have heard stories about the rear cables that link this 3-pronged pivot device to the drums. You will have noticed that there is a long cable towards the left drum and a shorter cable to the right drum. The story goes that there are different design lengths between pre-TS 60000 TR3As and the post-TS 60000 TRs. I don't know if this is true or not. But when you assemble these cross cables and adjust the handbrake, you may find that you might need to alter the length of one or both of these cross cables by up to 1/4 inch shorter for it all to work at the optimum.

 

When I installed new cross cables in 1990, I had to remove the yoke ends, run a die up another 1/2 inch or so and cut off the extra 1/4" from the threaded end so it wouldn't jam, once I set the yokes to where the tightness was equal.

 

The cross cables should droop when the handbrake is not actuated and they should have equal "tightness" when the handbrake is pulled "on". Otherwise, one side may pull "on" before the other and may cause your TR to spin to one side or the other during an emergency stop. You can check this with the rear end up on jack stands and ull the handbrake on one click at a time - then check the droop or tightness. As you get to about the 5th click on the handbrake lever arm, the drums should have equal resistance when you manually rotate the drums. Then by the 6th click the drums should be locked equally tight. The 7th click is to take up slack and wear during the next 20,000 miles or so. Then the long cable from the lever to the pivot arm can be re-adjusted to re-set the handbrake properly.

 

Remember that these are "fly-off" handbrakes - the reverse of every modern handbrake method since about 1965 or 1970. The early TRs were designed for rallies and racing as well as for fun touring and to swing the rear end of a sidescreenTR around a curve in an Alpine Rally or Mille Miglia, the driver could pull on the handbrake lever, perform his swing around the curve and then he just had to let go of the lever arm to continue.

 

When I park my TR3A in any public area, I pull on the hanbrake to the top. Then if someone wants to steal the TR, he doesn't know how to release the lever arm - so he gives up.

Link to post
Share on other sites

Thanks for all the great info. I am a long way from the point where I will need to configure and test the handbrake as I am currently stripping the frame ready for blasting. I wanted to understand how this mechanism worked while I'm making up the list of new parts needed. However I'll squirrel this info away until I need it. I plan to reassemble the frame and handbrake assembly and test it while the body is off. Then remove the handbrake lever to allow the tub re-installation.

 

Love the idea of the TR3 handbrake being an effective anti-theft device.

 

Stan

Link to post
Share on other sites

They are always different lengths.......but a TR4 has a wider axle and they are each therefore longer but still one long and one short, if that makes sense.

 

Dick..

Link to post
Share on other sites

No probs....your chassiss certainly looks in excellent condition.

 

 

:) It looks better than it should because when I replaced the floors I did some initial cleanup as at that time it was not my plan to remove the body. However Stuart reminded me I was only two bolts away from doing a full frame up restoration so I bit the bullet. I dont regret that decision one bit as it gives me a chance to get to all of the frame and easy access to the suspension etc. I have until April next year to work my way through the frame, suspension, brakes, rebuild the engine and install/test it. Then we get back to the body when it is warm enough again to paint.

 

Stan

Link to post
Share on other sites

Very nice Menno. Is that the correct orientation for the check straps ?. Mine were vertical to the frame and the bump stops on the axle would not have hit them.. I wonder if that is why the diff vent had poked a hole in the floor above the diff..

 

Stan

 

 

As far as I know (and after 4 seasons driving the car withou any problems) I'm pretty sure they are!

 

Menno

Link to post
Share on other sites

This is an interesting post for me because I have been wrestling with these cables for a long time. I have adjusted the rear drums until they are tight, then backed off two clicks so that the drum rotates freely. I then adjusted the cables so that any further adjustment would start to move the cylinder lever. This gives me a useless hand brake and trouble with the MOT.

 

An associated problem is that there is not much movement on the pedal. It is quite firm, wth very little movement, and I replaced the master cylinder with a nos item and it is still the same. This is better than too soft of course.

 

I must be doing something wrong.

Link to post
Share on other sites

The adjuster is fixed in position on the backplate, and as the adjuster is screwed inwards it will move both shoes towards the inside of the drum.

The slave cylinder is arranged to slide in the backplate so that it is self-centring. The handbrake lever acts at this point, too.

Because there is but one slave cylinder, one brake shoe is leading, the other trailing.

Because there is a self-servo effect with a leading shoe, this shoe has a greater effect if the car is moving forwards. Conversely, if the car is rolling backwards, the trailing shoe then becomes the leading shoe and assumes the more important role.

If the slave cylinder cannot slide, then only one shoe will be working properly and rear braking will be much reduced.

 

So, as long as your handbrake cables are doing their job )easily checked with the help of a friend), I suggest that you check that the slave cylinder is capable of sliding.

 

The standard TR2/3/4 handbrake lever provides the driver with tremendous leverage and normally provides excellent figures in the MOT.

 

Ian Cornish

Link to post
Share on other sites

Over time the cables stretch, which can make it hard to get sufficient adjustment. They have to be replaced or reworked like Don described. Also, the pivot can freeze up if it hasn't been greased for decades.

 

When adjusted properly, the cables should be slightly loose and appear to hang down in a curve when viewed from under the back of the car.

Link to post
Share on other sites

Stan - Looking at your check straps, they could be bent a bit towards the center like Menno and I have them. Also, put the rubber stops onto the axle as close as you can to the edge of the frame to be under the check straps. Yours look like they may be centered on the top of the frame centerline.

Link to post
Share on other sites

Stan - Looking at your check straps, they could be bent a bit towards the center like Menno and I have them. Also, put the rubber stops onto the axle as close as you can to the edge of the frame to be under the check straps. Yours look like they may be centered on the top of the frame centerline.

 

 

Yes, these pictures have been very helpful as I can see a few differences with my current setup. This is all getting torn apart and when I get to re-assembly I'll be sure to re-read this thread.

 

Stan

Link to post
Share on other sites

Yes Don, I agree.

 

TR2-3B only

 

Parts book gives different part nos with change from 9 to 10 inch rear drums on TR2 so logically they should go shorter with the return to 9 inch drums on post TS 60K cars. Moss/C&B certainly acknowledged this in the early days but opted for the slightly longer cables that would fit both 9 & 10 inch drum cars. (to simplify stocks)

 

Cheers

Peter W

 

L & R are different length by a good amount of inches on all the TR2-4 cars

 

TR 4 cables are a least 2 inches longer than their TR2-3 equiv.

Link to post
Share on other sites

Peter - Thanks for the explanation.

 

I bought my rear brake cross cables from C & B back in 1988 when I went through the stock-room on Manor Road to select all my needs with Russell Scott. The total came to about $3600.00 CDN when the £ was at $2.35 CDN and it was all air shipped to Montreal.

 

My early TR3A has the 10" diameter rear drums.

 

Cheers

 

Don Elliott, Original Owner, 1958 TR3A, TS 27489 LO

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...

Important Information

Please familiarise yourself with our Terms and Conditions. By using this site, you agree to the following: Terms of Use.