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PostPosted: April 25, 2013, 8:20 pm 
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Lonnie,

The Flaming River MGB/Cobra rack came in, although I didn't get around to playing with it 'til after I got back from a trip to Texas, and dealt with a few 'honey-does'.

I built a little jig (that almost sounds like Gilbert and Sullivan) to hold the rack at its designed height so that I could assess how it would work. At first glance it looks fine. I can position it fore and aft to get Staniforth's 75 degree included angle on the steering arm for Ackermann, and the pinion shaft runs at a reasonable angle. It almost looks like a stock MGB rack would have worked, but there's no guarantee the long pinion shaft on the stock rack wouldn't have interfered with something without trying one for real.

I've ended up with a need for a 3 1/2 inch tie-rod extender, which I will have two of them made next (a machinist I'm not), before coupling the tie rod to the steering arm and cycling the suspension and steering to ensure no interference between tie-rod and LCA - but at first glance I think I'll be Ok.

I will likely go quiet for a while now - while I get the couplers made and catch up on my backlog of Springtime garden chores.

(Edit: PS - If I were starting over again I would make the lower LCAs longer so that I could have used the slightly shorter and MUCH cheaper MII rack, but time is money, even at my low labour rate, and I couldn't face throwing away my new LCAs or doing suspension design all over again .... The bottom br*ckets would have been easier to make too!)


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PostPosted: April 27, 2013, 11:54 am 
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It looks good, Warren. And, that pinion shaft looks like a very good fit - low and short, hence reachable by going under headers, intake or whatever else might be in the way.

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

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PostPosted: May 7, 2013, 10:14 am 
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Thing of beauty!

Toolie looked after me again with some nice machining for my tie-rod extenders - he previously shortened my steering column for me back on page 3 or 4. I didn't make life easy for him either. When I bought new tie-rod ends (why re-use 12-year old ones ...) the young lady at the parts desk said 'inners or outers' to which I of course replied 'outers'. If the inners had the same taper they might have made life easier, because the outers are M14-1.5 LEFT HAND. On the bright side, it now means that I have an extender that acts like an adjuster, with M14-1.5LH on one end and UNF9/16-18RH (to fit the MGB/Cobra rack) on the other.

Sorry for the picture on the porch railing - I couldn't take on in situ because I used the interlude to do some gardening and to start getting the boat ready for launching. All the 'stuff' in my workshop gets piled in, on and around the boat while I'm working on the Locost. When I'm working on the boat, guess where the junk goes ...


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PostPosted: May 7, 2013, 10:34 am 
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Quote:
extender that acts like an adjuster, with M14-1.5LH on one end and UNF9/16-18RH (to fit the MGB/Cobra rack) on the other.

Good lookin' bit of kit there, Bro! Be sure to include jam nuts on that adjuster, or your toe-in might become toe-out and vicey-versey!

Quote:
Sorry for the picture on the porch railing - I couldn't take on in situ because I used the interlude to do some gardening and to start getting the boat ready for launching. All the 'stuff' in my workshop gets piled in, on and around the boat while I'm working on the Locost. When I'm working on the boat, guess where the junk goes ...


I have a one-car garage. When I'm working on the front of the Slotus, junk gets stacked on the rear deck. When I'm working on the rear of the Slotus... Well, you understand. :mrgreen:

Good hearing from you, Warren, and good to know you're makin' progress!
Regards-
JD

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PostPosted: May 7, 2013, 1:19 pm 
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Thanks JD,

Yes, I'll be sure to use jamb nuts - I learned that lesson the hard way in other circumstances. I saved the M14-1.5 LH jobbies off the Isuzu tie rods, but still need to chase down some 9/16-18s for the MGB tie rods. Being Right handed should make that a wee bit easier!

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PostPosted: May 7, 2013, 2:48 pm 
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That adjuster looks slick. Did you have it plated?

How does the rate of the Flame River rack compared to the stock one?

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PostPosted: May 7, 2013, 3:49 pm 
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Warren Nethercote wrote:
still need to chase down some 9/16-18s for the MGB tie rods.

I bought a whole bag of 9/16" jam nuts from McMaster-Carr, because they don't sell less than a bag of them. I used 4. If you can't find them elsewhere, I can slip a couple in an envelope.


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PostPosted: May 7, 2013, 6:17 pm 
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Andrew,

Honestly, I don't know about the 'speed' of the ratio, although Flaming River describes it as 15:1 with 6.25 inches travel - I was focused on rack length and pinion shaft length when I made the decision. My Isuzu steering arm length may also confuse things and I have no idea how it compares to that of an MGB. There are apparently two ratios for MGBs - the chrome bumper cars had a 'faster' rack than the rubber bumper cars. The 15:1 may be the faster one, but I don't know.

Yes, the extender is plated - the extenders found their way into a batch job at an industrial shop.

Nick,

Thank you! I do have a local source and will try them first; but your offer is appreciated, especially since McMaster Carr won't ship to Canada. I must get myself registered with one of those drop ship places. The local motorsports types use a place in Calais Maine.

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PostPosted: May 7, 2013, 9:22 pm 
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Warren Nethercote wrote:
The local motorsports types use a place in Calais Maine.


I read "Calais" before I read "Maine" and started wondering why anyone would ship nuts from Ohio to Canada via northern France. :mrgreen:

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PostPosted: May 8, 2013, 9:55 am 
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Warren Nethercote wrote:
Andrew,

Honestly, I don't know about the 'speed' of the ratio, although Flaming River describes it as 15:1 with 6.25 inches travel - . . . There are apparently two ratios for MGBs - the chrome bumper cars had a 'faster' rack than the rubber bumper cars. The 15:1 may be the faster one, but I don't know.

. . .


Warren,

I thought I'd poke around and try to get an answer to that question since I'll be ordering a rack of some kind. The jury is out on this one, at least based on the references I have or could find online. Here's what I found. The opinions are not mine, just what I found.

1) 15:1 to 17:1 typical of modern sports sedans

2) 12:1 to 14:1 "fast" or "quick", perhaps better suited to track cars versus street cars for most drivers.

3) Race cars -- I couldn't find anything based on what I have on hand

Again, this is not my personal opinion. I would like to find something with more objective reasons for calling them "quick" like some kind of measure of human performance or something based on driver experience. Some sources talked about lock-to-lock turns too. If one rack takes 3.3 turns and another 2.25, that give you a decent feel for how things might change with one versus the other. In some ways that is more appealing rather than 15:1, which is "move the wheel 15 degrees and the tires turn 1 degree." That seems like a hard ratio to guarantee and be assured of with all the variation in steering gear a rack like Flaming River might end up attached to in real life.

Any smart guys out there have better information?

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886


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PostPosted: May 8, 2013, 12:13 pm 
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Lonnie-S wrote:
1) 15:1 to 17:1 typical of modern sports sedans
2) 12:1 to 14:1 "fast" or "quick", perhaps better suited to track cars versus street cars for most drivers.
3) Race cars -- I couldn't find anything based on what I have on hand

Any smart guys out there have better information?

Cheers,


I'm not nearly as smart as many here, but I'll add some 2 cents here based on my research:

1. The whole "ratio" thing is left over from the recirculating ball steering days. IT is commonly used 'cause the hot rod guys still are mentally in that place.

2. This standard was replaced by another measurement -- "inches of rack travel per turn."
16:1 is roughly 2" of rack travel per turn.
14:1 is roughly 2.36" per turn.
12:1 is 2.62" per turn.
10:1 is 2.88" per turn.

3. Some donors and their inches per turn (based on numbers I gathered off of the 'net):

Chevette -- 1.6" per turn
Miata -- 1.77" per turn
Gen IV Camaro -- said to be 2.1" (standard) and 2.3" (sports) but mine was 1.6" per turn.
Fiero -- 1.5" per turn
Pinto -- 1.26" per turn

4. The circle track guys are dumping their manual slower racks for new, faster racks (ie, faster than 3" per turn) with power steering. The upshot is that guys like me can buy a virtually new (never installed!) slower manual rack for "Cheap" -- in my case, 2.5" per turn, 18" wide, for $165 delivered. Having said that, I've spent almost that much getting the thing hooked up to the steering arms and steering shaft.

5. Some other parts to this math problem:

- Faster racks mean, all things being equal, higher steering effort. IF you've got a torn a rotator cuff, or if you want your girlfriend, mistress and/or wife to drive this, keep this in mind. Anything over 2.5" per turn generally requires either power steering or an ape to drive the thing, all things being equal.

- shorter steering arms mean quicker steering, longer arms mean slower. If you use a quick rack and short arms, you're gonna have very quick steering. Oh, and all things being equal, more effort.

- Smaller diameter steering wheels mean faster steering and higher effort too.

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PostPosted: May 8, 2013, 1:33 pm 
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So the Flaming River MGB/Cobra rack is 6.25 in. travel/3 turns lock-to-lock = 2.1 inches per turn. Not super 'fast', but not 'Pinto-slow' either.

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PostPosted: May 8, 2013, 2:11 pm 
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Warren Nethercote wrote:
So the Flaming River MGB/Cobra rack is 6.25 in. travel/3 turns lock-to-lock = 2.1 inches per turn. Not super 'fast', but not 'Pinto-slow' either.


(nodding)

Depending on your steering arm length, yeah, it will be pretty responsive I'd think.

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PostPosted: May 8, 2013, 2:53 pm 
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geek49203 wrote:
Warren Nethercote wrote:
So the Flaming River MGB/Cobra rack is 6.25 in. travel/3 turns lock-to-lock = 2.1 inches per turn. Not super 'fast', but not 'Pinto-slow' either.


(nodding) I wondered what that rattling noise was! :mrgreen:

Depending on your steering arm length, yeah, it will be pretty responsive I'd think.


As a long-time MGB driver/racer, I can testify that in the MGB, that rack was quick, nicely responsive without being "twitchy".

Now, if you put it on a car with different steering arms, etc, all bets are off, but the movement of the MGB rack its-own-self is certainly quick enough!

:cheers:
JDK

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"Gonzo and friends: Last night must have been quite a night. Camelot moments, mechanical marvels, Rustoleum launches, flying squirrels, fru-fru tea cuppers, V8 envy, Ensure catch cans -- and it wasn't even a full moon." -- SeattleTom


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PostPosted: May 8, 2013, 11:20 pm 
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GonzoRacer wrote:
As a long-time MGB driver/racer, I can testify that in the MGB, that rack was quick, nicely responsive without being "twitchy".

Now, if you put it on a car with different steering arms, etc, all bets are off, but the movement of the MGB rack its-own-self is certainly quick enough!


Now, there you go, a "real life" evaluation from someone with experience on street and track. If it's "fast" enough to use in a race car, it should certainly satisfy we street car types. Thank you, JD.


@geek49203:
Thank you as well. I think the inches per track concept should be more useful since the needed math to figure out how far your wheels would turn based on the steering linkages (arm, etc.) you actually have, or plan to design should be pretty straight forward.

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886


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