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PostPosted: July 28, 2013, 8:28 pm 
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Somewhere near the top of the previous page I suggested to Lonnie that in a little while, or words to that effect, I'd be installing the MGB rack. "A little while' turned out to be the top of page 2. I've been doing lots of 'not locost' stuff - refurbishing boats for the sailing club and officiating at regattas, but this week my wife's nephew was here (unfortunately for my Mother-in-Law's funeral, who missed getting to her hundredth birthday by four months). This was his last day before going back to Calgary and SWMBO chased us out to the workshop to keep us occupied. What to do?

We started off by fitting a new FF1 tube (not strictly FF1, because my front end is like the Aussie Collins chassis) and then chopping the old one off. The original version had been hanging out front like a useless appendage and would interfere with the bottom radiator outlet.

Then we made up a rack mount like Uncle Ron's, bending up the CP19 and CP20 pieces out of 2 x 1/8 flat bar that I had lying about. CP19 had to be sculpted a bit, because the MGB rack mount holes are spaced quite far apart, so CP19 interfered with FF3. In the next day or so I hope to add the diagonal (CP21) piece, as per Uncle ron's Figure 4.31, "The Steering Rack Supports". Once I drill for the rack and bolt it in I will cycle the rack and deflect the suspension to check for interference and bump steer on the right hand side; all being well I will then get around to the LHS suspension.

All being well is the operative word: I have another regatta coming up, but I claim it's the journey that counts (but it is amazing how much you achieve in 3 hours with a little wifely encouragement).


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Isuzu Pickup/SR20DE, +401 COLD frame
Build Log: viewtopic.php?f=35&t=11601


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PostPosted: July 29, 2013, 9:27 pm 
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Good stuff, Warren. The MGB rack looks like an excellent fit.

I take it "Uncle Ron" = Ron Champion?

Regards,

Lonnie

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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: July 30, 2013, 7:17 am 
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Yes: Uncle Ron = Ron Champion :D

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PostPosted: March 16, 2014, 3:31 pm 
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Here I am, slinking in from Page 3 .... fortunately, I am one of the people for whom the journey is as much the satisfaction as the driving. The wind was blowing like stink today and the temperatures were a bit too warm to keep the ice hard enough for ice-boating so I went out to the workshop and blew some of the dust off. It was time to do a bump steer check before moving forward.

I bolted one of the spindle support jigs to the RHS hub and inverted it to hold a cheap laser level (I stopped the disc from rotating by driving a wood wedge into the caliper). I stood up an ice-boat runner plank mould against my sailboat as a target and went to it. It would be too much to ask for perfection at the first attempt: after a bit of trigonometry I found 1/16 inch of toe-out per inch of bump, so per Staniforth, I need to lower my rack. I hope not much, lest I have to do surgery on the rack mount, but isn't that why the Lord invented hack saws and welders?


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Build Log: viewtopic.php?f=35&t=11601


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PostPosted: March 16, 2014, 5:55 pm 
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That looks good, Warren. 1/16" isn't bad for a 1" bump, but it does look like lowering the rack will get rid of it. Raising the steering arms would work, too, but not so easy.


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PostPosted: March 18, 2014, 8:19 am 
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Had another go at bump steer measurement last night. I moved the rack down arbitrarily 1/4 inch or so to try things out and it moved me into a minor toe-out for bump and droop situation (with max toe-out about half of the first try). This is 'rack too long' space per Staniforth. I guess when Staniforth refers to adjusting with shims he does mean shims! So I'm happy that I am in a 'bump steer adjustment achievable by shims' area with my rack and can move on to other bits of the front end.

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Build Log: viewtopic.php?f=35&t=11601


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PostPosted: January 1, 2015, 6:27 pm 
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Hi Warren,

I'm going through your build log with more than casual interest in your steering gear setup. I've known for a while that I'd need a custom rack, but now I'm getting into the design of the front suspension and the interplay of the steering rack with it.

Initially, in the suspension design software I have, I postulated a traditional mounting location for the rack (behind the front frame) and some arbitrary, but realistic dimensions for everything. The tie rods had a forward sweep just as yours do. However, I got very poor results for bump steer. Long story short, I let the software seek an optimal location for the rack given my dimensions, and it found an excellent location, numbers-wise. Now, I've got to see if that location is actually do-able with the real (Haynes-like) chassis I have. It looks to me like the rack will have to go in front of the front frame to make that work. That's not the end of the world, but behind the front frame works better for other mechanicals in the area.

Getting to the point, you mention Allan Staniforth's "included angle" concept and I'm wondering what bump steer result you've been able to achieve using it and your forward-sweeping tie rods? Have you worked on it further since your March posting?

Thanks, and Happy New Year;

Lonnie

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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: January 1, 2015, 10:41 pm 
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Hi Lonnie,

I've been stalled for (quite) a while. I sold my previous iceboat last spring and building a replacement has been my priority. It's done, but for some tune-up after my first regatta of the winter (See photo) and I look forward to getting back to the car build. But before I get back to welding I have a heck of a lot sawdust to clean up - don't need no spark-induced fires!

The Staniforth 'included angle' is an Ackerman tool, and it drove my rack placement (reading other logs I might ask if I should have worried, but I went for 100% Ackerman to be conservative). The rough bump steer results a few posts (and many, many months ago) bracketed positive and negative toe on bump at two rack positions, so I presumed (and still do) that shimming should get me to acceptable bump steer. Since I located my rack ends on the plane connecting the steering arm to the instant centre (at least in the design: whether I achieved that in steel is an open question) the included angle-driven rack location should have no effect on bump steer, accepting of course that shimming represents deviation from the ideal (or maybe return to it?). Of course, moving the rack fore and aft (changing included angle) changes required tie-rod length, but as long as the rack ends lie on the line to the instant centre a geometric study should confirm no effect on bump steer per se.

I too thought I would go the Maval or Flaming River custom MII-based rack route, but after my first suspension design I compared my desired rack length to various stock racks and found that I was within a half-inch or so of the MGB. So, pragmatically, I changed (increased as I recall) my front track and did another suspension iteration to confirm that my design still worked. I recall that I needed to fiddle the track another eighth or so, and after that I declared victory, since I was probably working inside the tolerances of my physical model.

Thank you for dragging me back from page 3!


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PostPosted: January 2, 2015, 10:58 am 
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Thank you, Warren.

I'll bet ice sailing is fast with what must be a pretty low coefficient of friction on your boat's blades (?).

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: January 3, 2015, 9:07 am 
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Lonnie-S wrote:
I'll bet ice sailing is fast with what must be a pretty low coefficient of friction on your boat's blades (?).

And I'd bet that it's colder than a well-digger's arse!

Good to hear from ya, Warren! Happy 2015!
:cheers:

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Quinn the Slotus:Ford 302 Powered, Mallock-Inspired, Tube Frame, Hillclimb Special
"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: January 3, 2015, 9:51 am 
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Lonnie and JD,

Yes it's fast. With low drag on the ice you sail at 3 to 4 times wind speed (about 15mph wind that day), although even a few inches of snow on the ice sends drag skyward and speed downward. Dressing properly involves layers, because you work hard while sailing, and can get too warm. Nothing so disconcerting as having your glasses fog up inside your goggles. But in between races you often add a layer because you get cold standing about.

Best wishes,

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PostPosted: May 1, 2015, 8:46 pm 
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Here is where I admit envy of the guys doing 3-D CAD design work. My front suspension is in place (I say in place: close examination will show tack welds and the rack isn't bolted down) so it's time to work out the rad and nose mounts and figure out a bumper to keep Nova Scotia DOT happy. The second picture is a crude mock-up of nose and rad. The nose needs to drop an inch or two which means I'll need a hood blister, but the rad fits inside with room for fan and hoses. So I think I'll start with fitting the nose first .... I may need to narrow it a smidgeon too.


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PostPosted: May 2, 2015, 7:13 am 
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Hey Warren! Glad you finally thawed out after that ice-boat race! How did you do in the race, anyhoo? Win the "Almost Hypothermia" class, did ya???

Making progress on the project car too... That's a good thing! Keep chippin' away at it, you'll be driving soon.

:cheers:
JDK

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JD, father of Quinn, Son of a... Build Log
Quinn the Slotus:Ford 302 Powered, Mallock-Inspired, Tube Frame, Hillclimb Special
"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 2, 2015, 10:07 am 
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Does anybody use "travel bars" to get the right rack length? They can be made adjustable. They can make bump steer go away.


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PostPosted: May 2, 2015, 10:22 am 
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You do look like you're getting close to a rolling, running vehicle, Warren. I just marvel at the fact your chassis isn't all oxidized after sitting as bare metal. If I did that here at the coast, I'd be spending 2-3 days taking off light rust with emery cloth and wire wheels.

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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