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Progress in DIY TR3 Rack and Pinion Steering Conversion

Moss Motors
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Ken1945 Ken L
Brockville, Ontario, Canada   CAN
Well I am into the DIY conversion of our TR3A to rack and pinion steering. The cowl is off and I have measured the bump steer of the stock steering setup.

The TR7 rack (sourced via Triumph Experience) is positioned on a temporary mounting platform to allow me to try different rack positions and measure the resulting bump steer numbers, but I am waiting for some Spitfire tie rod ends to start evaluating rack positioning to minimize bump steer.

Mean while I have built a slip ring setup to fit on the upper steering column and retained the use of the original horn and turn signal switches. The only feature lost is the" intermittent" self cancelling feature since the switch unit now rotates with the steering wheel. I had to use a relay between the slip ring pickup and the horns since the horns draw 15 amps which is too much for the slip ring pickup. There is lots of room in the TR7 U joint that joins the upper and the lower steering columns for the wires from the horn and turn signal switches to come out and fit into the slip ring with little danger of pinching the wires.

Spacers have been turned allowing me to transpose the Steering Arms similar to the Moss approach.

Hopefully in the next couple of weeks I can determine my ultimate rack position and tie rod lengths and start working on the permanent rack mounting brackets which will be similar to the SC Group design.

I will keep you updated on the progress.

Ken
1953 MGTD
1960 Austin Healey 3000, BN7
1962 Triumph TR3A
1962 Jaguar Mk II sedan

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triumphrick Avatar
triumphrick Silver Member Rick Thompson
Masaryktown, Florida, USA   USA
I m just a few weeks behind you in installing the kit I bought over ten years ago from British Restorations in Roanoke.

His kit was put together using a Mini steering rack.

That was a very clever way to transfer the horn and turn signals! I may have to look this over, as I am not looking forward to mounting the MGA lever under or on the dash...one of the ways of doing it.

How are the copper slip rings mounted to the block?

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

I am not starting with a kit I am doing it all myself including determining the best position for the rack so wish me luck.

Here is a little more than you asked for regarding the slip ring:

The white plastic is Delrin turned to an OD for a light press fit for the ID of a 2" copper plumbing union which was used to provide the slip rings. I also used 1/16 brass pins to pin the copper rings in place to the Delrin and put some Gorilla Glue between the rings. [They are not going to move!)

The Delrin is about 1.5" long drilled 3/4 '' to fit over the steering column and counter bored 1.375" by .5" deep to clear the outer steering column tube. This gave me enough length to easily accommodate the 4 slip rings.

I used two set screws between rings 1 and 2 to fasten the Delrin to the steering column (that's why you see a wider gap between rings one and two).

The spring loaded pick up plungers are made from #10 brass screws turned to .150 with a 0.240 head. Above these are springs that engage with more #10 brass bolts that are screwed through the centre of a short length of 5/16 UNF bolt end. This assembly then threads into the Delrin block and forms the connection point to the wires that go to the turn signals and the horn relay

The electric connection from the steering column wires are via small brass tubes that a model shop carries with the wire end fitting into the next size larger tube (the 1/8" OD call it the outer tube). The outer tubes are connected to the various slip rings by threading a wire thru a radial hole in the slip ring and Delrin to intersect with the axial holes for the outer tubes and threading it out thru the 1/8 holes to accept the outer tube in the front of the Delrin allowing it to be soldered to the outer tube before the tube is pressed into the Delrin. I then soldered to other wire end to the slip ring and filed the ring smooth.

The only modification I did to the original horn turn signal switch was drilling a small hole between the fixed disc and rotating disc and putting a small #4 self taping screw in there to lock the two together.

Let me know how you project progresses.

Ken

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triumphrick Avatar
triumphrick Silver Member Rick Thompson
Masaryktown, Florida, USA   USA
Thank you Ken, that is an awesome amount of detail, just what I need to replicate what you have done.

I have seen a few of these but was happy to see what you have done.

Ken1945 Ken L
Brockville, Ontario, Canada   CAN
No problem if you have any questions simple ask. You will notice from the photograph that the brass tube for slip #1 ring is drilled right beside the slip ring to make electrical contact and is also soldered to the side of the ring.

If you get a chance can you post some photos of the kit you are using. What is the length of the mini rack between the inner tie rod end spheres? The TR7 rack is 22'" which is a quarter inch shorter than the inner tie rod ends of the original worm and peg set up.

triumphrick Avatar
triumphrick Silver Member Rick Thompson
Masaryktown, Florida, USA   USA
I'l be happy to post up pics when we get to that part....I have the rack and column stowed away right now

This is the part that I am having the hardest time understanding...

I just cant visualize it with it mounted..

"The electric connection from the steering column wires are via small brass tubes that a model shop carries with the wire end fitting into the next size larger tube (the 1/8" OD call it the outer tube). The outer tubes are connected to the various slip rings by threading a wire thru a radial hole in the slip ring and Delrin to intersect with the axial holes for the outer tubes and threading it out thru the 1/8 holes to accept the outer tube in the front of the Delrin allowing it to be soldered to the outer tube before the tube is pressed into the Delrin. I then soldered to other wire end to the slip ring and filed the ring smooth."

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

If you look at image 0971 you see the 4 brass tubes on the front end of the delrin insulator:

There are three of these axial holes that are drilled all the way through the length of the delrin. Keep these holes close to the outer diameter of the delin but not touching the slip rings since you need to clear the u joint. when you install the lower steering column
The 4th hole where the tube sticks out proud of the front delrin surface is only drilled to a depth to just before it touches slip ring two. This is the tube that is electrically connected to slip ring one.
There a then a 1/8" radial hole drilled thru to each of the three back slip rings. Each of the radial holes must intersect with a different one of the 3 axial holes.
The next is the challenge; threading a wire through the radial hole and then out through to the front of the delrin via the interconnected axil hole.
Once you have the wire threaded through to the front of the delrin you solder the front end of the wire to a length of 1/8" OD brass tube. You then gently pull the wire back and press in 1/8" brass tube until you feel increased resistance when the end of the brass tube is getting to the radial hole. You then solder the wire to the slip ring and file smooth. This should complete the electrical circuit from thru the brass tube to the slip ring.
Repeat this for the other 2 slip rings.

Ref: Img .0980
You see 4 wires coming out of the end of the upper steering column. Each of these wires are soldered to an approx. 3/4" length of small brass diameter tube that is a slip fit into the 1/8 OD brass tubes. Once you have the u joint is in place these wires will go out the opening created by the u joint part the connects to the upper steering column and the trunion portion of the u joint. Be sure you leave the wires from the steering wheel switches long enough to go thru the u joint and turn back easily to be plugged into the 1/8" brass tubes. This should create the electrical connection from the steering wheel switch to the appropriate slip ring.

I hope this clarifies it for you. If not send me a PM with you phone number and we can talk.

Ken

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CJD john durant
Southlake, Texas, USA   USA
Very neat and well thought out!



John
Southlake, TX

'55 TR2

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

It solves one of the reasons people say they don't want to convert to R&P steering. All for $20 Cdn. worth of material and brass bolts plus $20 Cdn. for the socket and relay for the horn circuit and a few hours of enjoyable work since every day is a Saturday for me. It sure bets spending $200 Cdn for a kit for remote switches.

I have the TR7 rack and it is only 0.25 inches or 1% shorter than the comparable measurement between the inner tie rod ends on the original set up.

Hopefully I will get my Spitfire inner and outer tie rods this Wednesday and can start confirming my position for the rack.

It will then be on to cutting steel and welding the brackets for the rack.

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johnstydo Avatar
johnstydo John Styduhar
Hermitage, PA, USA   USA
I also did a DIY rack and pinion conversion on my TR3B using the TR7 rack. I ended up shortening and rethreading the TR7 tie rods to fit TR4 steering arms and tie rod ends. I didn't bother with turn signals or horn since this is a vintage racer.

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

I never thought of using TR4 steering arms, I would expect that they do not have the 5 degree angle from the vertical that the tie rod taper hole has for the TR3. I will have to try a get a drawing of TR4 arms of the web.

Did you design your own conversion? Do you remember where you positioned your rack? Any issues with bump steer, I expect you would be more critical of this as a racer than I will be as a cruiser?

johnstydo Avatar
johnstydo John Styduhar
Hermitage, PA, USA   USA
Yes, I did my own conversion based on what I found on the internet. I positioned the rack front-to-back over the front lower wishbone inner pivots and laterally between/over the pivots. The vertical position was set so that the tie rods were as parallel to the front lower wishbone as possible at ride height. The new mounting brackets do not interfere with the original steering mounting brackets so their removal is not necessary. I also used the TR7 lower steering column/U-joint and upper knuckle to connect with the upper section of the TR3 split steering column. I mocked up the complete steering system when fabricating the mounting brackets. You may also have to bend back or remove the lower steering column mounting bracket which is welded to the left-side spring tower. I have not checked bump steer but did not find any unexpected steering responses when the car is on track over the last 4 years of racing, although my suspension is stiff and travel is minimal. The steering response with the TR4 steering arms is very quick.

Ken1945 Ken L
Brockville, Ontario, Canada   CAN
John,

Thanks for that information, it confirms what I had in my plans and just like you, I am mocking it up and realized I will have to bend back the support arm to make clearance for the lower steering column. I have got dimensions for the steering arms of the TR4 and TR4A so I can do some evaluation of alternative approaches.

I decided I would check bump steer on the original setup as well as after I complete the modification just to satisfy my curiosity, since lots of individuals on various forums quote increased bump steer as the reason for not doing such conversions.

I did a similar conversion on my Jaguar Mark II a number of years ago and have not experienced any issues with it other than an increased turning circle but since I don't park in underground garages very often, its a non issue.

Thanks again Ken

johnstydo Avatar
johnstydo John Styduhar
Hermitage, PA, USA   USA
The following link has information on the stock geometry for TR3/4.

http://www.tildentechnologies.com/downloads/TRsuspension.PDF

Ken1945 Ken L
Brockville, Ontario, Canada   CAN
I am well into my conversion of my TR3’s steering to rack and pinion. I got my used Spitfire inner and outer tie rods to evaluate alternative setups with some quantitative measurements before committing to fabricating the mounting brackets for the TR7 steering rack.

As a starting point I measured the bump steer of my car with the standard worm and peg steering system. Bump steer was measured with the wheels pointing straight ahead, turning left and right at 40% of capability and at 80% of capability. This gave me a base to at least meet but ideally improve upon.

Positioning of the rack:
Back and Forward position - the rack was positioned over the fulcrum point of the front suspension A arm and frame.
Vertical position – the rack was positioned vertically to get the inner tie rod visually parallel with the lower suspension A arm with suspension set at the normal ride height.

Alternative 1-The first alternative evaluated, left the steering arms in their normal positions. This setup gave me bump steer numbers very similar to the stock setup.

Alternative 2 - The next alternative involved transposing the steering arms to opposite sides and adding a spacer similar to what is done in the Moss Motors kit. This allowed me to increase tie rod length by approximately 0.8 inches. I expected to see an improvement since the tie rod length is getting closer to the length of the lower A arm. This alternative provided an improvement (i.e. lower toe in variation with the vertical movement of the suspension) over both Alternative 1 and the stock setup.

The only concern I had with alternative 2 was the chance of additional stress on the outer tie rod during maximum droop since the taper hole is now 10 degrees opposite to what you would want it to be. Disconnecting the inner tie rod from the rack there was still plenty of freedom to raise the free end of the tie rod even with maximum droop so I will be proceeding with this set up.

Its now time to design my mounting brackets and start cutting steel.

I have included a summation of my results at the straight ahead position. Similar improvements were seen at the intermediate steering positions.

Stock TR Bump Steer measurements Percent change in toe in due to suspension travel

wheel raised ie spring would be compressed
Bump stop 167%
2" 100%
1" 25%
Normal Ride height 14" from wheel arch to Centre of wheel Normal at toe in at 1/8 inch
Wheel lowered ie spring would be extended
1" little change


Alternative 1 - with steering arms in original position, shorter tie rods and rack in place (tie rods parallel to lower A arm)

wheel raised ie spring would be compressed
Bump stop 183%
2" 100%
1" 43%
Normal Ride height 14" from wheel arch to Centre of wheel Normal at toe in at 1/8 inch
Wheel lowered ie spring would be extended
1" little change


Alternative 2 with transposed steering arms and rack in place with tie rod parallel to lower A arm

wheel raised ie spring would be compressed
Bump stop 110%
2" 62%
1" 25%
Normal Ride height 14" from wheel arch to Centre of wheel Normal at toe in at 1/8 inch
Wheel lowered ie spring would be extended
1" little change


Similar improvement was seen at the intermediate steering positions


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