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Progress in DIY TR3 Rack and Pinion Steering Conversion

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tr3gt Frans Smits
Eindhoven, NB, Netherlands   NLD
I am also preparing for a do-it-yourself rack and pinion conversion. Tomorrow I will collect a used steering rack from a TR6 to experiment to determine the correct height of it. How did you do this? And how do you get the pivots of the tie rods in line with the pivots of the upper and lower pivots of the a-arms?
Are you gonna shorten the steering rack?

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johnstydo Avatar
johnstydo John Styduhar
Hermitage, PA, USA   USA
Frans, you will discover that the TR6 rack is not the best rack for a TR3 conversion. Try to find a rack that is closer in measure between the inner pivots to the distance between the lower wishbone inner pivots on the TR3.

triumphrick Avatar
triumphrick Silver Member Rick Thompson
Masaryktown, Florida, USA   USA
We are slowly getting back to normal since the storm, and I do have a full manual that came with the kit I have for my car..

That kit was sold by British Auto and uses a Mini Cooper rack. Should be able to get it all down in the next few days.

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Ken1945 Ken L
Brockville, Ontario, Canada   CAN
Hi Fran,

John is correct, the TR6 rack is too wide.

You need a TR7 rack, the TR7 rack is just 6mm shorter than the comparable dimension on the TR3 centre link.

Try and get a rack with the aluminum mounting pads cast into the rack (see photo). This makes fabrication of the mounting platforms so much easier and allows you to go from the idler and steering box mountings on the frame and straight back using the bolt that holds the engine mount rubber damper to the frame ( see photo) as support for you bracket at the back. This avoids a cantilevered design and significantly simplifies design and fabrication.

Concerning determining your rack position as John said in an earlier reply in this thread :

-position the rack front to back over the frame pivot point of the front lower A arm.
-set the height of the rack such that the inner tie rod is parallel with the lower A arm when the car is sitting on the ground.

I took a measurement from the top of the fender wheel arch down to the centre of the front axle with the car on the ground (14 inches on my car) which allowed me to always bring the axle back to ride height even with the car on stands.

I built a wooden platform at the start that allowed me to raise and lower the rack with spacers and take my bump steer measurements and determine the height I want the rack at. ( see photo at the start of this thread)

I have completed my bracket design and will be buying the steel this week and hope to have the brackets complete in a couple of weeks.

For inner tie rods I will be using shortened and rethreaded TR7 tie rods. For outer tie rod ends I will be using Spitfire tie rod ends, TR4 ends wilt also work.

Good luck with your project, Ken


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Ken1945 Ken L
Brockville, Ontario, Canada   CAN
Fran ,

You will also need a lower steering column from a TR7 and the universal joint that connects the lower steering column to the upper steering column on a TR7..

I assume your TR3 already has a two piece steering column.

Ken

tr3gt Frans Smits
Eindhoven, NB, Netherlands   NLD
Thank you guys for all your valuable help. I had only borrowed the TR6 rack to determine the correct height. Optimizing the angle of the steering arms will then also take place. Then I will test if there is still bump and how much. I am going to do this as Ken describes. If the result is satisfactory, I also know how wide the rack should be from centre pivot to centre pivot. I hope the TR7 rack is correct.
I found a drawing with a compact but clear description of the geometry this afternoon. It has helped me understand it. I have attached it.

Ken: can you tell me the distance from centre pivot to centre pivot of the TR7 rack?


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Ken1945 Ken L
Brockville, Ontario, Canada   CAN
Hi Fran,

The TR7 rack is 55.88 CM (22 inches ) from the centre of the ball to the centre of the ball to the best of my measuring ability.

According to the frame drawings the arm lower pivot points are on 44.45 cm centre distance.

Ken

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Ken1945 Ken L
Brockville, Ontario, Canada   CAN
The project is progressing. The electric fan is mounted to the rad and all wiring is in place. The mounting brackets are roughed in and the TR7 rack and pinion will be fastener to them next week. It will then be time to modify the TR7 lower steering column to fit.


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johnstydo Avatar
johnstydo John Styduhar
Hermitage, PA, USA   USA
The TR7 lower steering column should fit without modification.

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Ken1945 Ken L
Brockville, Ontario, Canada   CAN
Hi John,

It may have been possible to move the upper steering column back into the cockpit an inch or so and use the original TR7 lower steering column but then I loose the space I need fit the slip ring and pick up bracket for my horn and turn signal hook up.

I ended up cutting about 1.25 inches out of the centre of the lower column and then turning a 1 1/2 inch length on each section down to 1/2" and then fitting in a 3" long 1/8" wall cold rolled tube over the two sections and welding them back together. I figure with over 1 1/2" of weld around the circumference of the joints I should have plenty of torsional strength.

I think that you could lift the car with the two brackets I have installed to position the rack and pinion.

I finished the dry fitting of every thing today and hope to complete the final assembly in the next couple of days and try it out.

Our club has a 250 mile fall colour tour on Sunday but I think we will take the 1960 Austin Healey for that . I prefer to test TR3 out locally for a week or so.

johnstydo Avatar
johnstydo John Styduhar
Hermitage, PA, USA   USA
Here is a drawing of the TR front suspension from the manual. When doing this conversion, be aware that the TR4 had two different steering arms, depending on whether or not you had caster in your front suspension. The difference in the arms is the amount of droop when could help in getting the tie rods to be as parallel to the lower wishbone as possible.


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TRsuspension (1).PDF    312.7 KB

Ken1945 Ken L
Brockville, Ontario, Canada   CAN
Had a good day today. The rack and pinion was installed along with the lower steering column and the rad with the electric fan. The toe in was set and the cowl installed.

I took the car out for a short test drive and I am pleased with the results so far. The car feels much tighter.

The only negative is the 4 turns lock to lock compared with the original 2 1/4 turns but I knew that when I started and in my opinion the improvement far out weighs the higher lock to lock number.

Hopefully tomorrow I will have time to install the grill and bumper and take it out for a longer drive.


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johnstydo Avatar
johnstydo John Styduhar
Hermitage, PA, USA   USA
You will appreciate the easier steering with the TR7 rack when the car is not in motion, especially if you have wide tires.

Ken1945 Ken L
Brockville, Ontario, Canada   CAN
I finished reassembling the car this morning and went out for a 30 mile test drive:

In my opinion the car was much nicer to drive without that dead spot in the middle of the worm and peg steering along with its heavy steering at low speeds.
The rack and pinion steering was light (particularly at low speeds) and responsive.
My turn signal and horn controls on the steering wheel worked fine.

Unless anyone has any questions or I have any issues I will probably no post any more entries on this conversion.

tr3gt Frans Smits
Eindhoven, NB, Netherlands   NLD
Hi Ken,

It is good to hear that you are satisfied with the conversion. I also learned a lot from this thread and it helped me making choices, until then I was in doubt because of all the half-information that came from everywhere. I couldn't find a used TR7 steering rack here locally but I ordered and received a new one. But this gives a new problem because the tie rods are not as easy to remove as from the old steering racks. This is necessary to get new thread on it after shortening. But I will also solve these problems. At the moment I am making a mould for the supports like you have made.
Thank you for all your advice and I hope you will enjoy driving your car.

Frans

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