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Everything posted by JMortensen
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Did you measure the control arm length?
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Any news on this? Curious to see if both sides need fixing as a general rule...
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Dynalites are about 3.5 lbs each as I recall. Toyota 4x4 calipers are about 9, and I think stockers are about 7. That's all rough memory, but I think it's safe to say that the two calipers are not so heavy that it will cause problems. Totally unnecessary for braking, but might be the cool thing for drifting, I dunno.
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Not really. Since a corner requires effort from the front AND rear tires (although less from the rears), you can't really separate out the turning to the front and the acceleration to the rear. There is always going to be some unused portion of available grip. Rear drive leaves front grip on the table, front drive leaves rear grip on the table. An AWD car can drive the fronts and rears, and having a little drive to the front, since weight transfers to the rear, is going to be faster than driving just the rears.
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You need a gap between the clutch pedal and the master adjustment clevis. If you install a new master and adjust the rod just a tiny bit too far, then when the pedal is released the port that opens to the reservoir won't open. When this happens, pressure trapped in the system stays trapped in the system. As you drive the clutch fluid gets hotter and expands, so the clutch acts as though your foot is dragging the pedal just a little bit. Harder to get in and out of gear, clutch starts slipping, etc. Eventually it will be to the point where you can't drive anymore. If you let the system cool down for a few hours or overnight, it drives fine again until you put heat into the system again. Been there, done that. You'll occasionally see the same mistake made with brakes, where a person will complain that the brakes just get progressively stronger until the car will barely move and there is smoke coming out of the wheels. Same exact problem but with brakes instead of clutch.
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To be nit-picky, if you're good at setting up a car, it's likely because you use the scientific method. It's not the publishing that makes something scientific. http://www.sciencemadesimple.com/scientific_method.html The steps of the Scientific Method are: Observation/Research Hypothesis Prediction Experimentation Conclusion Maybe I've read your previous posts wrong and you don't work in a scientific manner. Perhaps you do an understeer dance and sacrifice a hamster before a race, I don't know. I kinda doubt it though.
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Science doesn't win races? I seriously doubt you take that stance when trying to figure out what to do to make your car handle better in order to win a race...
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The Honda was faster than the other cars on that day. That proves nothing about which platform is better. AWD has a distinct physics advantage. The quoted fastest lap time on youtube was 1:30.8. Your car went faster than that. Does that prove that a Datsun is faster than a Viper? Or does it prove that YOUR Datsun was faster than THAT Viper on THAT track on the day that you were there? I lapped a 2002 911 Turbo in a 20 minute session at Buttonwillow. Does that meant that my Datsun was faster than a 911T, or that I was faster in my Datsun than the dentist driving the 911T? Does it prove that Front Engine is superior to Rear Engine? I beat two different Vipers in my Toyota truck at autoxes. Does that mean that my Toyota was faster than those Vipers? Or that I was faster in my Toyota than those Viper drivers were at those autoxes? Does it prove that leaf springs are superior to SLA? Anecdotal evidence isn't proof or disproof of a larger theory. Anyone who says that FWD has to be slow is an idiot, and I think that's what you're getting at mostly, but this video proves nothing about the larger argument.
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Threaded collars don't fit on strut tubes
JMortensen replied to mclark999's topic in Brakes, Wheels, Suspension and Chassis
Buy the right sleeves for a 280. -
I need suspension help
JMortensen replied to Matt 78Z's topic in Brakes, Wheels, Suspension and Chassis
Weight of a .060" thick gusset and the welding wire to glue it in place isn't more than a couple ounces at most. I'm sure the weight of the sectioned part of the strut housing that I removed was greater than the weight of the gusset. Trying to think of an easy way to test flex now, because it would be good to have numbers to work with instead of intuition. -
I need suspension help
JMortensen replied to Matt 78Z's topic in Brakes, Wheels, Suspension and Chassis
The spindle itself is a lever arm that is about 3.5" from the middle of the bearings to the back side of the casting, and there is the "ear" that the spindle is machined out of which is another little lever arm for the strut to work off of as well about 1" long from the center of the spindle to the main thicker part of the casting. If the spindle came straight out of a solid casting, I don't think I would have done this mod. I think the effect here that we should be most concerned about would be camber loss in cornering. There may be some issues in supporting the weight of the vehicle vertically as well, with some corresponding neg camber loss under braking, but I think it's very analogous to the strut tower bar, where what you're trying to do is keep the neg camber and not lose it to either that ear flexing over under load in the case of the gusset or the strut tower flexing out under load in the case of the strut tower bar. Weight transfer = lateral g x weight x cg height / track width. Say that is 1.2g x 1200 (weight of one axle) x 21" / 53", or 573 lbs. So that outside tire is now having 1173 lbs of vertical pressure, but that's just the vertical load, and that doesn't account for the effect of the horizontal loading of the suspension through the twisting effect of the spindle as the tire tries to fold under the car. Here my math gets fuzzy, but I think if you just added the length of the levers to the 1' from the hub to the ground, you're going to get 1.375 x the weight, so really we're talking about 1612 lbs, but I think that is an oversimplification and too generous, because it is the convoluted shape that the forces are acting through that makes the structure weaker than the force would otherwise suggest. I think a large offset wheel would also skew the numbers further. Testing would tell the effects for sure, but for those who don't have the facilities to test, this is an easy modification to do and whatever distortion would be caused by welding is easily adjusted out by me, and certainly by most who would bother with this modification. -
I need suspension help
JMortensen replied to Matt 78Z's topic in Brakes, Wheels, Suspension and Chassis
Someone could do some FEA on it and tell you for sure, but for my $.02, the middle of the strut tube is an unsupported span, and the strength is close to the base. -
Vortex Generators on Undertray?
JMortensen replied to 260DET's topic in Windtunnel Test Results and Analysis
I don't think you use vortex generators to create laminar flow. You use them to create the opposite, a vortex. The idea is that when you have flow separation, it's better to keep the flow energized (as in a vortex), so that it can still do something when it hits the control surfaces. I think there might be a case for vortex generators on the underside for the same reason that AirTabs work. They will keep the flow headed in the right direction even if it isn't attached and laminar, but Richard has it right, if the surface is flat and smooth, there isn't going to be a huge boundary layer, so the vg's just aren't needed. -
I need suspension help
JMortensen replied to Matt 78Z's topic in Brakes, Wheels, Suspension and Chassis
Yep. Can't remember where I heard about this, but it seemed like a good idea and literally took about an hour to do both struts. Really easy. Too bad there isn't a way to do something similar in the rear... -
I need suspension help
JMortensen replied to Matt 78Z's topic in Brakes, Wheels, Suspension and Chassis
I wouldn't do droop limiters on a car with that light a spring rate. There's so much droop that you probably won't get to limit much. Just to show the problem, figure a 2800 lb 280 with 50/50 weight distribution and perfect corner weights. With 700 lbs per corner and 200 in lb springs, you're going to have 3.5" of droop. This means the limiter isn't going to do anything until the roll is 3.5" up on the inside. For the subframe mod, you'll see different people quote different numbers. I've never heard 5/16" up, always 3/4" or 13/16". What I did was to remove the little washers on the crossmember then drill another hole directly up from the stock hole on the crossmember. Then I cut a slot between the two holes. Using a bumpsteer gauge I moved the control arm pivot up until the bumpsteer was minimized. In my case I think it was 7/16" up to fix. -
I need suspension help
JMortensen replied to Matt 78Z's topic in Brakes, Wheels, Suspension and Chassis
OBX shouldn't add much understeer. I think if I were you I'd add adjustable TC rods to your list. Caster made a big difference in my car. -
Adjustable front control arm options
JMortensen replied to wheelman's topic in Brakes, Wheels, Suspension and Chassis
I don't know how far you have to go to get x amount of camber sorry. Someone who has recently installed adjustable arms might know... I really don't like any of the aftermarket rear arms on the market. The TTT ones have no bracing and the outboard end is just a flat plate. The new AZC ones have that funky inboard pivot. I know people have run it without trouble, but the design is not a good one IMO. The MM ones have rubber bushings and they have a ton of threads in bending. I do think the ones that I made are the best I've seen, but I'm not going to make any to sell or anything, so you would have to copy the design yourself. EMWHYR0HEN made a nice set with the toe link in the back, but Justin's copies weren't up to snuff. Not sure if those ever got fixed. Cary modified some stockers into an A arm with toe link with the toe link to the rear, those looked simple to make and looked really good too. -
Adjustable front control arm options
JMortensen replied to wheelman's topic in Brakes, Wheels, Suspension and Chassis
For your purposes I would be concerned with which one is longest at the full short setting. I'm guessing you're probably going to want to add camber with them, and I know some of the manufacturers make them so that the stock length is in the middle of the adjustment range. I like that the TTT parts can be ordered to size. Also keep in mind that if you adjust too far (roughly 1/2"), you might run out of tie rod adjustment, then you're into making tie rods, unless someone is manufacturing those now too... -
Looking for the area of a whale tail
JMortensen replied to JMortensen's topic in Windtunnel Test Results and Analysis
I don't know how you could have read what I wrote and thought that I didn't agree that it was effective. I can only surmise that you didn't read it. I was amazed at its effectiveness compared to the wing. Your "test" was worthless and the numbers completely unrealistic, the Nissan Comp numbers are also not believeable, but the wind tunnel results are pretty stunning, and I said as much in my email to McBeath which I posted on the other thread. "If you figure from the test previous that the tail made 253 lbs downforce, that works out to a Cl of 1.1, which seems VERY impressive for a spoiler." EDIT--I also said this: "I've been trying to consider the effectiveness of the whale tail vs wings, and I've come to the conclusion that the whale tail is VERY efficient at producing downforce when using the wind tunnel numbers when compared to the APR wing." -
What is the length of the control arms from center of inner to center of outer pivot?
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That's news to me, I thought because of the offset of the diff it was only the driver's side that had issues. How much did you lengthen the control arms, and how did you test for bind?
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Found some springs in a junk yard today
JMortensen replied to clutchdust's topic in Brakes, Wheels, Suspension and Chassis
I thought MSA sold their own blue springs. -
Looking for the area of a whale tail
JMortensen replied to JMortensen's topic in Windtunnel Test Results and Analysis
Thanks. The point was to compare the whale tail's efficiency to a wing, and it did way better than I expected. Whale tails work! http://forums.hybridz.org/index.php/topic/92212-wing-vs-whale-tail-spoiler/page__st__20