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Moist Lightning

Center Take-Off Rack & Pinion

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This has always been the confusing part of center mounted tie rod R&P. The civic one clearly has pivots only a couple inches apart. so did they make up for that design flaw with other suspension engineering?

 

Regardless i have wondered about machining big ole extension bars that thread into the center mount and place the pivot out at the standard location.

I've seen that done before. You need to support the extensions to avoid deflection.

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I've seen that done before. You need to support the extensions to avoid deflection.

 

Thanks for the input.

 

I think i found a pic of a braced extension 

 

manual%20rhd%20mustang%20rack%20reduced%

I'll have to do some more research, as this brace looks like it could get dirty and wear fast.

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I've seen that done before. You need to support the extensions to avoid deflection.

 

 

Thanks for the input.

 

I think i found a pic of a braced extension 

 

 

I'll have to do some more research, as this brace looks like it could get dirty and wear fast.

 

I've been looking around and it seems commonplace to have long extension bars with no brace. Both unisteer and steeriods do this. 

One of the longer ones i've found are the ford falcon unisteers

 

8001050-01-400x400.jpg

 

Could you elaborate on your experience? Did you or someone you know make one? did they have problems until they braced it?

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Well, if you read it online, it must be true.

 

I think it would depend on a multitude of factors, but I would like to see all those factors addressed before I made that mod to a steering rack.

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Well, if you read it online, it must be true.

 

I think it would depend on a multitude of factors, but I would like to see all those factors addressed before I made that mod to a steering rack.

 

Sorry, didn't mean to say I didn't think it needed it. Just trying to get as much info as I can. However unisteer and steroids are commercial manufactures, not just "oh i found some dude who wasn't bracing them and it seems fine."

 

anyway you said you've seen it done and sounded like you had some experience, is there any more you could share?

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For more it seems more like a question of intent.

 

I don't race. I don't even really drive aggressively. I don't think i would have any issues with there being some deflection in the setup, so long as the final feel was tighter and more crisp than what i previously had. And the deflection was not so great that i believed it to be a safety concern.

 

But the more aggressive the use, the more deflection gets created AND the more you would be concerned about that deflection.

 

Street vs track to me, at which point the potential for wear on the reinforcement bars would be unimportant, as it would be monitored along with the rest of the car.

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What about using a normal rack and connecting the two ends with a bar you can mount your new pivots to?

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What about using a normal rack and connecting the two ends with a bar you can mount your new pivots to?

Interesting thought. I hadn't considered this but it could be made to work well i think.

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I've been looking around and it seems commonplace to have long extension bars with no brace. Both unisteer and steeriods do this. 

One of the longer ones i've found are the ford falcon unisteers

 

8001050-01-400x400.jpg

 

Could you elaborate on your experience? Did you or someone you know make one? did they have problems until they braced it?

What's the point of center steer if you move the inner tie rod connecting point so far outboard that a traditional rack and pinion would not only work better, but be significantly simpler?  

 

I think there's some mis-information being spread here, not understanding the difference between Ackerman Angle and bump steer.  Moving the center pivot inboard will likely reduce extreme bump steer angles, but it WILL have an effect on Ackerman (the different angles the tires must turn in a corner to turn their respective radius.)  That has a bit more to do with the rack placement than the inner tie rod angle, but both are important.  We totally screw these all up anyway when we lower the truck, so whatever design you come up with will have to be sorted with the end ride height in mind.  

 

Simply offsetting the tie rod height will correct bump steer.  Ackerman is MUCH harder to fix, generally done by changing steering arm length and at least one control arm length.  

 

On any R&P, you can build extensions or cut the inner tie rod shorter.  I have a 2000 Chevy rack in my '49 Willys truck.  Just takes minor modifications to the tie rods as described above, and custom steering arms for front steer.  Chose the wrong rack and your steering wheel turns the opposite direction of your front tires.  Oops.  

 

MGB racks may be a viable option, and relatively tight ratio steering.  They are front mount and plentiful.  Too narrow, which is easier to fix than too wide.  

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The problem is that there are virtually no easily available racks that are narrow enough. They all start out too wide already. Those options that have been used are either difficult to find or expensive and custom.

 

Perhaps mg is the answer that has been missing, but up to now there hasn't been a magic bullet that didn't cost a grand.

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Sorry, didn't mean to say I didn't think it needed it. Just trying to get as much info as I can. However unisteer and steroids are commercial manufactures, not just "oh i found some dude who wasn't bracing them and it seems fine."

 

anyway you said you've seen it done and sounded like you had some experience, is there any more you could share?

I was just being cynical.

 

I have seen extensions done before, both with and without bracing. The bracing has been in the form of a pillow block style mount, but I am not sure how they addressed the wear issue. The comment about many variables, well the rack could possibly hold up to the stress of added extensions if the rack is very large to begin with and the extensions are of a strong material, but there are also suspension geometry factors involved. If the steering geometry is not perfect  to begin with, there could be built in deflection that would exacerbate matters.

 

Short extensions are pretty common, but I don't know at what point the extensions become too long. My thoughts are all theory, as I have never dealt with this, but I am "in the industry" so my mind is continuously going, looking for potential pitfalls and possible solutions.

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I don't race. I don't even really drive aggressively. I don't think i would have any issues with there being some deflection in the setup, so long as the final feel was tighter and more crisp than what i previously had. And the deflection was not so great that i believed it to be a safety concern.

One of my concerns with deflection is wear in the rack, not solely performance. A manual rack will take more abuse than a power steering rack, but still, there could be a longevity issue with deflection.

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I wish I could climb under my MGB and take measurements right now, but its -10 outside and the front spoiler is a lightweight fiberglass race setup - likely brittle in this cold.  It looks about right, likely having to make an adapter for the outer tie rod ends.  The distance from inner to inner pivot looks damn close to stock Datsun.  A Midget rack would be narrow yet, and quicker ratio.  The best part is that they never wear out.  The bad part is that factory steering (column) joints are too light for a truck.  

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I was just being cynical.

 

I have seen extensions done before, both with and without bracing. The bracing has been in the form of a pillow block style mount, but I am not sure how they addressed the wear issue. The comment about many variables, well the rack could possibly hold up to the stress of added extensions if the rack is very large to begin with and the extensions are of a strong material, but there are also suspension geometry factors involved. If the steering geometry is not perfect  to begin with, there could be built in deflection that would exacerbate matters.

 

Short extensions are pretty common, but I don't know at what point the extensions become too long. My thoughts are all theory, as I have never dealt with this, but I am "in the industry" so my mind is continuously going, looking for potential pitfalls and possible solutions.

 

Thanks for sharing. I've done a bit more research on deflection. I also think i've got a solution but i'll start with deflection.

 

• Front steer tends to be the stronger than rear steer because when cornering the outside tire takes exerts the most force due to body roll/momentum pushing out. In a front steer vehicle the tie rod on the outside of the corner will be under tension not compression. This is why rear steers tend to bend rods more than front steer.

 

• I was also playing around with a deflection calculator but im not sure how much force is normally exerted on the steering. probably differs per vehicle.

 

Although, i've come up with a method that will keep the stock geometry as well as keeping the center takeoff close to stock config.

 

Earlier i mentioned the idea of replacing the steering box with an idler arm and attaching the center link to the rack. I quickly realized that the center link would pull away from the rack  as it rotates around the idler arms radius.

 

The solution is to use the center takeoff with cententral pivot points to connect the idler arms to the rack.

 

the next problem is that the stock tie rods off the center takeoff rack are too long. the solution is a short extension bar with some 10-11" tie rods. It would look like this but the tie rods would connect to two idler arms.

 

550px-Original_cavalier_inner_tie_rods.j

 

I just need to check if an idler arm will bolt up in place of the steering box or if a custom mount needs to be made.

 

 

What's the point of center steer if you move the inner tie rod connecting point so far outboard that a traditional rack and pinion would not only work better, but be significantly simpler?  

 

I think there's some mis-information being spread here, not understanding the difference between Ackerman Angle and bump steer.  Moving the center pivot inboard will likely reduce extreme bump steer angles, but it WILL have an effect on Ackerman (the different angles the tires must turn in a corner to turn their respective radius.)  That has a bit more to do with the rack placement than the inner tie rod angle, but both are important.  We totally screw these all up anyway when we lower the truck, so whatever design you come up with will have to be sorted with the end ride height in mind.  

 

Simply offsetting the tie rod height will correct bump steer.  Ackerman is MUCH harder to fix, generally done by changing steering arm length and at least one control arm length.  

 

On any R&P, you can build extensions or cut the inner tie rod shorter.  I have a 2000 Chevy rack in my '49 Willys truck.  Just takes minor modifications to the tie rods as described above, and custom steering arms for front steer.  Chose the wrong rack and your steering wheel turns the opposite direction of your front tires.  Oops.  

 

MGB racks may be a viable option, and relatively tight ratio steering.  They are front mount and plentiful.  Too narrow, which is easier to fix than too wide.  

 

As lock leaf mentioned there is no stock rack narrow enough and modifying a center takeoff is easier than shortening a rack.

You can look for one but many others have tried without success so far. I would love to be wrong.

 

However, the solution above would keep the stock geometry because the outer tie rods are still connected to an idler arm. solving the problem of akerman angle and bump steer.

 

And in regards to lowering i totally agree. additionally lowering without drop spindles also ruins the roll center because if the negative wishbones. Im working on ball joints and coils and though i might as well do R&P while i'm at it.

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Is this about power steering or something else?

What year is your 620?

 

I keep coming back to this question, is this about power steering or something else, and what year is your 620?

Are you looking to get rid of the 620 column?

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I keep coming back to this question, is this about power steering or something else, and what year is your 620?

Are you looking to get rid of the 620 column?

 

its a 72.5, its sloppy and there aren't many donors near me. I have a ka24de and would like power steering only because i want a tighter steering ration than a manual rack can provide. lastly my uncle was impaled by a 1pc steering column; so safety too.

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OK, so the idler arm you have is likely the same as the 521 and is reversible as I have done it, so if you put an idler arm in the place of the steering box/gear, you will have a complete steering system with no way to steer it.

What I did was put the idler arm where the 521 steering gear went like mentioned above, then I used a 720 power steering gear, I put it on the outside of the frame, the rear hole is shared with the idler arm, the front hole is drilled thru the frame and a sleeve needs to be installed(welded in), then a brace needs to be welded on the top of the frame for the upper steering gear mount hole.

The Pittman arm needs to have the tie rod hole tapered from the bottom up half way so the tie rod can be inserted from the bottom.

The expensive part here is the custom center-link that needs to be made, you see you need a center link with a tie-rod connection on the passenger side, once installed the stock center-link is used to go from the 720 Pittman arm to the center-link tie-rod connection, the custom center-link needs to be strong, mine was made from a single piece of round steel bar turned down to my requirements.

Here is my setup, here is the center-link installed with the stock center-link installed between the custom center-link and the Pittman arm.

100_0154.jpg

Here is the view of the 720 power steering gear installed on the outside of the frame, you can see the stock center-link going from the Pittman arm to the custom center-link, notice how close that arm is to the idler arm on the driver side, it rubs on it.

100_0155.jpg

Here is the idler arm mounted where the steering gear is supposed to be, the frame was rebuilt once in this photo, you can also see here how close the Pittman arm steering rod is to the idler arm, it basically rubs.

DSCN0628.jpg

Here is the custom center-link connection.

DSCN0629.jpg

Now one has to keep in mind that I had already converted over to a ball-joint frontend in these photos and I have 1990 Nissan hardbody V6 disc brakes(dual piston/vented rotor), I use a 720 tilt column, but if you were to use a non-tilt column I believe it will bolt right into you existing column mount and I believe that all your column accessories will bolt right onto that column with very little effort, there is a little more involved here like the column firewall connection that I will not get into here, but if one takes their time and thinks about it, this can be put together in such a way that it will almost look stock.

I have had to rebuild that idler arm/720 steering gear area of the frame a few times now, but this was my first try and I think it has worked out pretty good fir 12 years now.

Just to cover all the bases, here is the area that I had to rebuild for the 2nd time in this photo, our early Datsun trucks were not designed for power steering put on this way, but if it is done right the first time it likely will last a long time, by the way I beat the crap out of this truck, I haul massive amounts of weight on this truck, that also likely plays a part in this part of the frame falling apart.

DSCN1216.jpg

Here is one of the loads below, on another occasion I rolled onto the scales at 7200lbs, the truck weighs 3400lbs.

DSCN0393.jpg

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SO here's the skinny:

The MG Midget R&P has a roughly 19" center to center distance measured from the inner tie rod pivot, so its nearly identical to stock Datsun 620 steering.  Its shorter in overall width, so you could make a custom adjuster to mount any outer tie rod to the rack and correct the track width.  The way the rack mounts is via clamp, and its adjustable so mounting it to the truck couldn't be easier, and you will not need an idler arm, which is a ridiculous idea with a R&P IMHO.  Lock-to-lock is 2 1/2 turns, so very quick ratio.  And they're dirt cheap.  There are several on Ebay for under $50.  

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...and the MGB R&P is roughly 45 1/2" wide end to end.  Usable with no modifications if I measured properly.  

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its a 72.5, its sloppy and there aren't many donors near me. I have a ka24de and would like power steering only because i want a tighter steering ration than a manual rack can provide. lastly my uncle was impaled by a 1pc steering column; so safety too.

I like the idea of a power rack, but I bet you don't really need power assist in such a light vehicle. Adding a MGB rack would probably lighten the feel enough to satisfy that requirement. I would love to see you use a power rack though, for my own curiosity.

 

I did a write-up a couple years ago on a 320 balljoint conversion. In the thread, I showed how to modify the column to terminate it at the firewall. I like that mod, not only for the reason you mentioned, but also because it allows you more room in the engine bay and more options for re-routing the steering shaft.  Here's the link - http://community.ratsun.net/topic/34698-320-balljoint-conversion/

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SO here's the skinny:

The MG Midget R&P has a roughly 19" center to center distance measured from the inner tie rod pivot, so its nearly identical to stock Datsun 620 steering.  Its shorter in overall width, so you could make a custom adjuster to mount any outer tie rod to the rack and correct the track width.  The way the rack mounts is via clamp, and its adjustable so mounting it to the truck couldn't be easier, and you will not need an idler arm, which is a ridiculous idea with a R&P IMHO.  Lock-to-lock is 2 1/2 turns, so very quick ratio.  And they're dirt cheap.  There are several on Ebay for under $50.  

 

Thanks for measuring. Not sure it will be short enough though. distance between LCA's is 16".

It would depend how high you need to mount it to compensate, and if the oil pan will allow it.

 

Good info here: http://community.ratsun.net/topic/52633-620-with-sr20det-with-ac/page-2

 

Not sure why you don't like the 2 idler arms. it would keep geometry stock so there is no worrying about bumpsteer and what not. Is there something i'm not seeing that makes it a bad idea?

 

You have convince me to try looking for an end take off solution again. Trying to remain open minded.

 

Edit: another benefit of a center take off is the pinion can be further out making it easier to attach a new column.

 

OK, so the idler arm you have is likely the same as the 521 and is reversible as I have done it, so if you put an idler arm in the place of the steering box/gear, you will have a complete steering system with no way to steer it.

What I did was put the idler arm where the 521 steering gear went like mentioned above, then I used a 720 power steering gear, I put it on the outside of the frame, the rear hole is shared with the idler arm, the front hole is drilled thru the frame and a sleeve needs to be installed(welded in), then a brace needs to be welded on the top of the frame for the upper steering gear mount hole.....

 

 

It's funny you posted, i was just looking through your post on a diff thread.

 

I would do some things differently but it proves the concept. I do have a question though. you said the frame needed reinforcement due to the pressure added by the power steering. However, properly mounted the idler arm should just swing, it shouldn't be transferring much pressure to the frame. I don't understand what caused your frame to fail. maybe i just interpreted the info wrong?

 

I see you attributed it to the weight somewhat. maybe its just too much load and a rusty frame to start with?

 

Edit: i'm a little slow sometimes. the pressure is only applied when there is a force applied to the tyres that would otherwise shift the steering. With power steering you holding everything in place and forcing it to absorb the energy instead. However, i do think the fact that you load so much weight into the vehicle attributes to this and under normal loads and regular driving should be fine. For off roading or heavy loads like yours reinforcement would be a good idea.

 

I like the idea of a power rack, but I bet you don't really need power assist in such a light vehicle. Adding a MGB rack would probably lighten the feel enough to satisfy that requirement. I would love to see you use a power rack though, for my own curiosity.

 

I did a write-up a couple years ago on a 320 balljoint conversion. In the thread, I showed how to modify the column to terminate it at the firewall. I like that mod, not only for the reason you mentioned, but also because it allows you more room in the engine bay and more options for re-routing the steering shaft.  Here's the link - http://community.ratsun.net/topic/34698-320-balljoint-conversion/

 

Thanks i'm trying to get through it but i'm a visual person and all the pic are broken. Ill figure it out just might take me a bit longer.

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If someone has the time to map out all the suspension points accurately in x y z coordinates i can run it through my suspension program. Like has been mentioned bumpsteer is minimised by locating the pivot points on the intersection plane between the top and bottom control arm points, you can also fine tune it more by moving the rack forward and backward as well. Im happy to play around with different length rack dimension to find the best position.

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Until my last rebuild of the frame 3/4 months ago the bolt that is shared by both the idler arm and 720 steering gear was smaller than the other bolts, it would stretch under the stresses and eventually break, once it loosened a little before it broke when I turned the wheel the actual steering gear would move a little sideways both directions depending on which way it was turned, this movement was hard on the frame, it has a larger bolt/sleeve now.

Also the shared bolt sleeve stuck out of the side of the frame a little, this left air between the frame and and the 720 steering gear, also I didn't sleeve the front steering gear bolt and it is not sleeved to this day, I used a plate on the inside of the frame that allowed me to tighten that bolt very tight without crushing the frame, all this stuff adds up in the end, if I ever did this to a 521 frame I would do some things differently, that was my first time at power steering on a 521 and it was done before this forum even existed, the year before I converted over to a ball joint front end also, I had issues with that also, but it has all been worked out.

The loads I carry may be a part of my frame issue, but these other things likely played a much larger part in the issue, yes I would do things differently now, everything would be rock solid if I did it now, ever since I put that larger bolt in the shared hole my steering has not changed since(it normally gets loose after a month or so), normally I have to tighten that shared bolt every couple months until it finally breaks, I tried tightening that bolt which is larger now and could not move it, my steering has not changed either.

That sleeve I am talking about with the smaller bolt has to be reamed out to except a larger bolt.

Also you have to keep in mind that the 720 steering gear is way taller top to bottom than the 521 steering gear, being the Pittman arm tie rod connection for the steering is much lower that puts more sideways/twisting stress on the frame than the stock steering gear ever put on the frame, another thing to keep in mind is with the stock steering gear it is hard to turn the wheel when not moving, so one doesn't do that often, with power steering it is always easy to turn the wheel putting a lot more stress on the frame more often, I tried to not turn the wheel when I was not moving to much at first, but after years of use one forgets about that stuff and just drives the truck.

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Thanks i'm trying to get through it but i'm a visual person and all the pic are broken. Ill figure it out just might take me a bit longer.

I pay for a 3rd party hosting account, so the links should be good. I can see them on my end.

 

Can you do me a favor and check the pics in this thread for me? I had another guy comment that he couldn't see the pics here - http://forum.expeditionportal.com/threads/172482-FJ62-LS-Swap-Lone-Star-Sleeper-Stoffregen-Motorsports

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