sector shaft bore

[Mark Strang]

I have TC 7801 which has taken me entirely too long to finish but I'm getting there. I am working on the steering box. Over the years I have gathered three steering column/steering boxes. I've taken them all apart recently and found that they are all different regarding the sector shaft. In one unit there is no contact between the sector shaft and the top plate. It has bout 1/8 inch clearance. The previous owner claimed excessive steering wheel play!. Another has a Tompkins kit. The last unit has a washer welded to the top cover to take up clearance. Supposedly, this unit was inspected and rebuilt by an "expert" who said it was good to go! Two of the worms are looking pretty worn and the pegs on two of the sector shafts are not in very good condition. The intriguing unit that has the Tompkins kit on it has had the sector shaft bore opened up and needle bearings installed. Was this a common modification in the past? If so is this a good system to use and are the bearings easily identified so replacements could be purchased if necessary? Given the fact that two of the units need at a minimum a new sector shaft, the Tompkins kit unit is attractive especially with the needle bearings in the bore. Interestingly the "good" sector shaft from the Tompkins unit is about 0.0015" larger than the the other shafts and won't fit the other sector shaft bores. Both it and the worn gear appear to have had very little use so at this point I'm leaning toward the Tompkins setup if the bearing issue is not a deal breaker. Comments?

[Ray White]

Personally, unless you are committed to it for some reason, I would do as numerous others have done before you and ditch the Bishop cam and fit a VW or Nissan box. A slightly smaller steering wheel can help off set the lower gearing which is, of course, the inevitable compromise.

Perhaps reading this will help.

https://mwthemachineshop.com/vw-vs-bc-steering

[Steve Simmons]

Most of the modern replacement sectors are made oversized to account for bore wear. This makes zero sense to me, since you'd have to be really lucky to have exactly the right amount of wear for it to fit correctly. And if you have less wear, you have to bore out an original unworn component to use the sector.

Needle bearings aren't common but you do see them from time to time. See page 19 of Franz's thread below for photos of his needle bearings (scroll down a bit):
https://www.mg-tabc.org/forum/viewtopic ... &start=360

There are those who say the Thompkins kit is a bad idea and those who swear by them. The most important thing is to make sure the kit fits the sector properly. FTFU did a video explaining the issue:
https://www.youtube.com/watch?v=f_3sUaoK7Fc

It's an expensive piece, but if you don't trust your sector shaft then it's not a bad idea to buy a brand new one. The consequences of a failure are pretty high.

[Duncan M]

If you do not have the factory original worm then you probably have a nice paperweight. FTFU used to sell proper worms made in Canada through Bob Grunau. FTFU has not had them in stock for some time now. Nearly all of the aftermarket worms sold over the decades have been junk that do not work properly.

The idea of needle bearings to run the sector shaft through is probably about the worst idea ever. No kidding. Don't do it, unless you will only be driving you car on and off a trailer.

[stephen stierman]

Why are needle bearings a bad idea? Just curious.......

He could always take it to a machine shop and have them fit a bushing and ream for his existing sector shaft. They always have a bit of on center free play, it is just the design. If the car is wandering all over it isn't necessarily the steering box. I set the toe on mine as specified for the TA/TB cars and it was just fine after that.

[Mark Strang]

Well, I think I have the issue I was facing all figured out. After much checking and measuring and disassembly and reassembly I have come up with enough good parts to make a very satisfactory steering box. The good sector shaft has virtually no wear on it because it has been chromed or hardened and polished. The worm that was associated with this shaft is also in great condition. I simply took the best box housing and reamed out the sector shaft bore about 0.002 and the good sector shaft fit perfectly. No need to worry about the needle bearings which I think are not a bad idea unless there's something of a historical design problem with them. The top of the sector shaft is about 0.005 beneath the cover plate so I'm going to use the Tompkins assembly that I have to allow me to adjust the play properly now and later with ease. The only thing left is to mag particle the sector shaft and drop arm. Now I'm moving on to the tie rods ends etc. Looks like I have spare parts now that hopefully won't be needed.

Seems to me that the steering should not have a lot of slop. It certainly wasn't designed to have a lot of play and there are other manufacturers that use basically the same design. I've been a TD person for decades and am constantly told that TC steering is bad and that there are pros and cons about the use of shims, toe in, VW boxes, etc.. I'm going to go original and am convinced that if all parts and clearances are proper in the front that I will have good steering but I won't know for sure until the car is done which is probably a year from now.

I helped a friend install a VW box a couple of years ago. He put one in from Silvers. He loved it when we were done. I was glad for him. One of the three boxes that I have is his. Upon opening it up recently I discovered that there was a tremendous amount of clearance from the sector shaft to the cover plate. I stuck the Tompkins kit on the box, adjusted it, and there was no slop when bench tested. The peg was just sloppy in the worn and slightly worn. He could have just installed a kit although he does like the feel of the VW setup. To each their own.

[Steve Simmons]

I have two TCs with BC box and one with Datsun (which I prefer greatly over VW). Both options have their pros and cons. But both will also drive dead straight down the road with minimal input from the driver. If a TC is wandering all over the road (like many do) then there's something wrong.

I'm not aware of any issues with needle bearings for the sector shaft, but I also don't feel like they would make much difference. I'm also concerned how much meat needs to be reamed out to fit them. There isn't a lot there to begin with.

[timberstone]

Marc,
Thank you very much for the detailed and descriptive post about the internal options that you have for the Bishop Cam steering box. The exercises that you are going through with your steering box are typically what it takes to bring one “back to life,”

MGTC 0820 went through such options such as you described -- it had the Bishop Cam steering box with drop arm chromed and machined to match with new worm gear and also the Tompkins Kit on top.
It steered OK but may not have had the tie rod and links set up fully, so it seemed hard to steer. Then switched its Bishop Cam for the VW steering box (as provided by the Machine Shop in Colorado Springs).
Steers fine, but really does miss the quicker response to turning. So now there is serious thought about going back to the Bishop Cam box…
One just has to be a perfectionist -- like you – to really get the proper results from the Bishop Cam Steering box.

[timberstone]

Some further thoughts:
Intrigued by the proposal to use needle bearings around the drop arm just as described in Franz Tenbrooks posts. However, do not believe that the drop arm shaft in the bore creates a major source of friction or wear. Just need to keep the interior of the box lubricated and have a seal on the bottom of the bore to prevent leakage of lube and intrusion of dust and debris.
Share the concern about whether there is enough metal in the box to bore out the added diameter for the needle bearings, so did not venture down that road. (Maybe some Bishop Cam boxes have more metal in them than others.)
However, seems that the end-play on the worm gear in its fore-and-aft positions, inside the box, is as much a concern for friction and slop as the drop arm up-and-down positions. Maybe these bearings and races on the worm gear ends are not discussed as frequently, but these also wear and so certainly are as important.

[Franz Tenbrock]

Hi
My steering had the needle bearing when I got it 6 years ago, the second steering I have I got 4 years ago from the bay
The new sector doesn t fit this steering, so I use the steering with the needles
I sl see in spring how it will work
I can change to the one without the bearing
Just driven out the garage, no play, much better

[stephen stierman]

These steering boxes or relatives of them were used in many British cars of the period and beyond, TR's, Big Healeys, AC's and Morgans and more. My 1969 Morgan Plus 8 has a Cam Gears box which uses the same bearings as the Bishop's Cam TC box and the internals are very similar. They all have a slight amount of on center "lost motion". They are not rack and pinion and there is no reason that the car should wander all over the road, my Morgan doesn't. My TC did to some degree even with a pretty decent steering box, thought seriously about a VW conversion. I got curious, why does the manual show the TA/TB cars with a little more toe in? Same cars for the most part. I increased the toe on my TC and it steered like my Miata, almost that is, it was transformative.

[timberstone]

Don't think MGTC 0820 will ever, or even wants to, "steer like a Miata" --- but does want to eliminate the "lost motion" at center of travel as much as possible.
Earlier tried to eliminate the spring-loaded track rod ends by performing a modification described by this forum's moderator. Involved substituting with eye sockets that had balls.....
Encountered some clearance problems with the pitman drop arm of the converted VW kit, so did not pursue it further. Now see that Moss has a new conversion kit that has a straight pitman drop arm -- so maybe that could take the balled socketed eyes for the track rod.

[Ray White]

Before M.O.T. inspectors were able to condemn cars for excessive "play" in the steering, I think it used to be common place to increase the toe in to hide the effects of worn steering components. It does what is intended but has a downside; there is considerably more wear to the tyres!

[Duncan M]

Some further thoughts:
....However, seems that the end-play on the worm gear in its fore-and-aft positions, inside the box, is as much a concern for friction and slop as the drop arm up-and-down positions. Maybe these bearings and races on the worm gear ends are not discussed as frequently, but these also wear and so certainly are as important.

The ball bearings and cages on the ends of the worm do not seem to wear much when the box is properly adjusted. My experience, at least. You want very close to zero end float on the worm. This end plate shimming is always to be done before the top plate shimming. Did you know the end plate is stamped with the year date the box was assembled? Many boxes have the original end plate because they do not wear.

Last time I went through my BC box was close to 10,000 miles ago when I last rebuilt the front end. Box has not needed any top plate (I use the flat top plate) or end plate adjustment, and all the links have not needed any adjustment, either.

The Autocar magazine article posted on this site in interesting because it http://www.mg-tabc.org/library/images/bishop-cam1.jpg shows wear towards the top and bottom of the shaft. Thing is, the hard chromed sector shaft is a lot harder than the cast iron of the box housing that forms the sector shaft bushing. Wear actually occurs more on the cast iron, or the bronze bushing most all boxes have been fitted with. If they have been fitted with the (thin) bronze bushing, all that is needed when the wear to bushing occurs is to press out the old bronze and press in a new one.

[Mark Strang]

Stephen, my '70 Morgan 4/4 has a similar steering box. I can drive it at 70 and the car tracks straight. Therein lies my theory that TC 7801 should track properly when all is said and done. I help my BIL with old Jeeps and Willys in the U.P. of Michigan where we spend the summers. If I recall, the steering on his 1953 Willys has the same type of box as well as tie rod ends. His Willys tracks just fine.

[stephen stierman]

Mark, my Morgan is the same way and there is a slight bit of lost motion also in the steering box as all of them have, but it does goe nicely down the road. My TC did not have much more free play than my Morgan and the tie rod ends are in good shape as are the king pins, however it was not pleasant to drive requiring constant correction as many of them are and I was considering a VW conversion. One night I was perusing the shop manual and noticed that the toe settings for the TA/TB cars was 1/2" while the toe for the TC is 1/4". Why is this, they are virtually identical up front? Nobody could give me an answer and still hasn't. I got curious and increased the toe to 1/2" and it was transformational. Now you can say the tires will wear out quicker, can't say that happened during the couple thousand miles I drove the car a year, now do you drive the car 10,000 miles a year? I don't care whether anyone tries this or not, I am just telling you that I forgot all about that VW conversion. Is it like my Miata? Well not exactly, but it isn't far away. Mr. Verona (French Blatter) I believe has done this also, maybe he will chime in.

[Mark Strang]

Stephen, I'll make a note and tie it to the steering box for when I get it set up and ready to run, I experienced a similar situation with both of my TD's. One is concours(and a driver) and the other is strictly a driver. They would always wander even with the all components brought back to spec. I dropped the tire pressure about 3 pounds in the front tires and there was a good improvement. I then set the toe in tighter than specs( can't remember the number) and now the car tracks nicely without wandering. Amazing what a few little changes can do. As far as tire wear is concerned, tires are cheap given the cost per mile of enjoyable driving. These cars are just a hobby. Hobbies cost money. We aren't changing tires every year anyway.

[stephen stierman]

Mark,
Good points. Let's factor in the cost of the VW conversion and see how that affects cost of operation compared to tire wear if that is a problem. I have driven a TC equipped with a VW conversion and it was fine, but I do prefer the faster feel of the original box when all is set up properly.