JJLudemann's Design Thread

[DanW]

I got some 7075, and then, without marking it, tossed it into my small shop repository that contained all else -- 2024, 6061 etc.

Is it now forever lost... or is there some way of knowing which pieces are the super alloy without having a microscope and a lab full of metalurgists to look at it?

Thanks,

Chirs

A niton gun(nuclear analyzer) can tell you the chemical composition. Most metallurgical inspection companies can check them for a reasonable fee. Good reason to mark your material stock.

[R. Pare]

I got some 7075, and then, without marking it, tossed it into my small shop repository that contained all else -- 2024, 6061 etc.

Is it now forever lost... or is there some way of knowing which pieces are the super alloy without having a microscope and a lab full of metalurgists to look at it?

Thanks,

Chirs

These are chemical kits available that you can use to identify the major alloying elements. Here's one:

http://koslow.com/metal_test_kits/15...e758a6b8d1bac4

Just Google "metal test kit" and you should get a bunch of hits.

Once you get them sorted, you will want to mark them. Easiest thing is to just buy a variety of cheap spray paints in different colors, make a chart of which color you want to use for each alloy you expect to ever have, and spray each piece both when you first get it in and then on any leftovers. Paint pens of different colors works as well.

So does just marking them with a Sharpie "7075', "6061", etc.

[nulrich]

An old machinist's trick: put a mixture of lye (sodium hydroxide) and water on bare aluminum. Here's a chart showing the resulting color difference between various alloys.

6061 and 7075 are easy to differentiate with a hammerless center punch. 7075 is a lot harder, so the indentation is noticeably smaller.

Anodizing can reduce the fatigue life of aluminum in very high cycle applications, although a 50% reduction in fatigue strength is unusual, under normal conditions it's quite a lot less. A dichromate seal after anodize restores fatigue strength to essentially the same as bare aluminum (although it reduces hardness).

7075 is very susceptible to stress corrosion cracking, which can reduce fatigue strength by 90% (!), so it's especially important that it be coated. I prefer anodize (with a dichromate seal), as the resulting coating is much more durable than iridite.

Nathan

[Christopher Crowe]

-- and sorry for shanghai-ing the thread.

[R. Pare]

Anodizing can reduce the fatigue life of aluminum in very high cycle applications, although a 50% reduction in fatigue strength is unusual, under normal conditions it's quite a lot less. A dichromate seal after anodize restores fatigue strength to essentially the same as bare aluminum (although it reduces hardness).

Actually,about half the tests that I have read have shown the 50% reduction, but also quite a few showed no reduction at all! Go figure....... Since none of use are going to go to the lengths of actual controlled, lab-grade testing and highly controlled anodizing processes, the safe thing is to plan for the worst.

Actually, in most of our applications, it isn't long-term fatigue that is the issue - the parts are most likely designed to be operating at well above the fatigue limit and actually much closer to the yield point. In those cases, the problem then becomes the strength and brittleness of the anodizing - it will crack at much lower stresses than the parent material, cause a stress riser, and the crack then propagates through the aluminum. Seen way too many times un-anodized parts that operated well for years without breaking get replaced with a new anodized part and break very quickly.

And Nathans advice on 7075 corrosion is spot on - it can start corroding VERY quickly after machining, and especially so if the coolant used is not of the correct PH. Best practice is to wash the parts off immediately after taking out of the mill or lathe, and then oil it.

Now - back to JJ's originally scheduled program!

[JJLudemann]

This may be something that's so obvious no one's ever mentioned it, but I can't find any references to this on ApexSpeed. It appears Suzuki GSX-R1000 engines support OBD-II onboard diagnostics, which would automatically supply RPM, throttle position, coolant & oil temp., air intake temp., manifold pressure, outside pressure, battery voltage, O2 sensors, fuel injection times, gear position, and on and on. The stock engine doesn't seem to have a standard OBD-II connector, but maybe there's a non-standard one somewhere. I can't find it on the wiring diagram unless it's the totally unlabeled one in the upper right next to the ECU connector. I assume people with data acquisition systems are tapping into OBD-II data somehow, but I can't find info on how this is done. Also, I've seen mention of OBD-II to CAN bus adapters, which it seems would connect easily to CAN-bus data loggers. Is that how it's done? This guy:

Blue Monkey Motorsports / Cal Sportbike

has something that interfaces to a PC, and there are off-the-shelf OBD-II to Bluetooth adapters that will get the data into a smartphone, which can then use off-the-shelf applications to display everything. Like this:

Youtube video of Torque Android App & OBD-II Bluetooth adapter

This looks promising because you can use the phone's video camera, accelerometers, and GPS to make a pretty decent data acquisition system almost for free. Can one of these off-the-shelf OBD-II to bluetooth adapters be adapted to a motorcycle engine, and then are the commands compatible?

Is this all like "duh, everyone knows that" or is this all new? It looks like engines are finally getting complicated enough that I can understand them. (:-)

-Jim

[Jnovak]

My son Brian has this figured out. Our data system reads the ECU and gets all the data. I am no expert on this but I will point Brian to this post.

Thanks ... Jay Novak

[JJLudemann]

I do love the Internet so!

Yes, the OBD-II connector is the unlabeled one on the upper right of the wiring diagram. On the wiring harness it's located right next to the dealer-mode connector, which is also unlabeled on the wiring diagram. Sooner or later companies will learn not to try to keep things secret from the Internet... It's the pretty yellow and black plastic connector. So I found this great site that has a whole forum dedicated to hacking GSXR ECU's:

ECU Hacking GSXR Forum

And a sticky right there near the top is the ECU pinout for 2007-8 GSX-R ECU's. Did I mention I love the Internet?

B/Br: Sensor Ground E2
Bl/W: COV1 SSW
Bl/B: COV2 SPL
Bl/G: COV3 RXD1 (receive data)
Bl/Y: COS2 TXD1 (transmit data)
R: Vcc Sensor +5V DC

Still have to figure out what SSW and SPL are.

-Jim

[RobLav]

The 2011 ZX-10R has a CAN+ and a CAN- located on the ECU/connector. The pin location is in the AIM documentation.

[Wright D]

[FONT=Verdana]The AIM should be able to read in the CAN data from the GSXR too....we have done it for several different ECU's, even the new Performance Electronics ECU (EDGE, but not related to Gary)[/FONT]

[JJLudemann]

Sorry I haven't updated in a long time. Life gets in the way, sometimes. But I have been working almost continuously, and the body buck is nearly finished. I added a couple of updates to my blog:

Building the Body Buck: Part 1, Ribs & Foam
Fabricating the Suspension Attachment Points

-Jim

[Astro]

Hi JJ, I've been following your build-up for quite a while & I am seriously impressed with what you have been able to acheive, and also in a country which is not conducive to racecar manufacture. Your documentation of your processes and end product have enthused and inspired me. I plan to build a bike engined open wheeler for hillclimbing. As I can't afford to buy a suitable car outright, I am left to manufacture my own. I understand that this will probably result in a car which is more costly than to buy now,"but such is life". I notice that you use a Jasic 200A AC/DC tig welder. How would you rate this welding unit? Have you had any issues at all with yours? I have seen your welds and they look good. I am considering buying one. I have a 200A DC tig currently but would love to be able to weld aluminium and a foot control would be just fantastic. I look forward to ongoing documentation of your build.
Thanks, Pete.

[JJLudemann]

Hi JJ, I've been following your build-up for quite a while & I am seriously impressed with what you have been able to acheive, and also in a country which is not conducive to racecar manufacture. Your documentation of your processes and end product have enthused and inspired me. I plan to build a bike engined open wheeler for hillclimbing. As I can't afford to buy a suitable car outright, I am left to manufacture my own. I understand that this will probably result in a car which is more costly than to buy now,"but such is life". I notice that you use a Jasic 200A AC/DC tig welder. How would you rate this welding unit? Have you had any issues at all with yours? I have seen your welds and they look good. I am considering buying one. I have a 200A DC tig currently but would love to be able to weld aluminium and a foot control would be just fantastic. I look forward to ongoing documentation of your build.
Thanks, Pete.

Thanks for the interest. I've found the Jasic welder to work extremely well. Haven't had a single problem with it. The only deficiency is that when you plug in a pedal control, the welder automatically goes to full scale. In other words, you can't use the pedal to modulate between zero and 60 amps, for example. With the pedal, you only get the full range from zero to full power. The way I've gotten around this is to set the machine for DC pulse welding at maximum frequency (300 Hz.?) and I can then control the max power by adjusting the duty cycle. But at this point I don't use the pedal control at all.

As Nike says, "Just Do It".

-Jim

[JJLudemann]

I'm getting a little behind in my blogging, but here's the latest update:
Finishing the Body Master Pattern

Attached is a photo of the body buck just before I started making molds. I just finished pulling the last mold today, but that will be the subject of the next blog entry.

There was also another blog entry I didn't mention here:

Building the Body Buck, Part 2

Enjoy!

-Jim

[JJLudemann]

I have these dual-adjustable gas-pressure spring/shock units and I need to know the correct length for finalizing the suspension design. The manufacturer has lengths available from 260 to 290mm and the units aren't marked, so that's no help. With the shock at the full extension stop, I measure 280mm. With moderate force (20-30 pounds) it will compress to about 275mm, at which point it becomes difficult/impossible to compress further with my hands. Is this the length to use, as maybe that's where the damping really starts, or should I just design it so the shock is 280mm at full droop? I believe the mfr. offers 275mm but not 280mm, by the way.

Thanks,

-Jim

[S Lathrop]

To calculate the static length of the shocks, you need to start with the load that that corner of the car will have to support.

Say you have 250 lbs. at the tire, the motion ratio is 1" wheel movement to 0.9 " shock movement, you then have to support 277 lbs. force at the shock. Compress your suspension unit until you have 277 lbs. force and measure the length. That is you static length. Measure the force at 1 in. above and below that point and you can calculate the spring rates you will be seeing. I would guess that a spring rate in the 450 to 550 lbs./in. is where you will fall at both ends of the car.

In a car with bell crank suspension, the bell crank angle is critical. Because of this I prefer to have the free length of my shocks adjustable. From you description it sounds like you will need to design a droop limiting system for the shocks. As a starting point, I use 1" droop. I then install the springs to support the car at the correct ride height without preload so that the load of the car compresses the springs sufficiently to achieve the ride height I want. If I make a big change in spring rates, I can change the shock length to compensate. The amount of droop you allow for the suspension is a very important tuning factor in getting the handling just right.

[JJLudemann]

I would guess that a spring rate in the 450 to 550 lbs./in. is where you will fall at both ends of the car.

In a car with bell crank suspension, the bell crank angle is critical. Because of this I prefer to have the free length of my shocks adjustable. From you description it sounds like you will need to design a droop limiting system for the shocks. As a starting point, I use 1" droop. I then install the springs to support the car at the correct ride height without preload so that the load of the car compresses the springs sufficiently to achieve the ride height I want. If I make a big change in spring rates, I can change the shock length to compensate. The amount of droop you allow for the suspension is a very important tuning factor in getting the handling just right.

Thanks so much for the quick answer. It's because bell crank angle is critical that I want to make sure I've got this right. So you can only get preload if the damper is at full extension, unless you have an external droop limiting system, right? Would you ever want preload on a properly adjusted F1000 car? Maybe to keep the ground effects at the proper ride height under all but heavy loads?

So assuming we don't want preload and the bell cranks have to be in the correct operating angle range, the ride height adjustment has to be done first with the spring support rings on the spring/damper units to get the bell crank angle correct, and then with the pushrod length adjustment, right? And the first adjustment will change with different spring rates. You could also do it by adjusting the spring/damper chassis mounting points, but that's heavily loaded and an adjuster could be heavy. I'm thinking about having spring/damper mounting points that could be changed out to give a different length range, but not infinitely adjustable ones.

Why is the max droop critical? Once the spring is at max extension, you get no more normal force on the tire with additional droop. What am I missing here? Maybe the springs have to be soft enough to extend to 1" droop (for example) to maintain tire contact pressure.

Thanks so much,

-Jim

[S Lathrop]

Droop limiting is very common. Most often it is used at the front of a car to control chassis movement, in particular roll. It also controls front ride height within limits set by the spring rate and the spring travel.

At the top levels of racing, teams will setup dampers with springs so that they have a standard load at a certain length. In this way, you can change the spring damper in the pit lane and the car will go to the previous ride height. When I do a spring change, I calculate how much to adjust the push rod to get the ride height I want with the new spring rate. I can make a spring change in the pits in a few minutes and have the car as close as it would have been had I changed the springs on the setup pad and adjusted the ride height.

With an above ground front roll center, you get some jacking force as the car corners. With low spring rates, this results in the front rolling more and the front ride height rising during cornering. With stiffer springs this jacking tendency is not as great because the car does not move as much with a change in loads. The solution often chosen is to preload the front shocks. This limits how far the shock will extend as the front is unloaded. Zero droop is the condition when the front does not drop when it is jacked up. The springs have enough preload to support the car at ride height. When you increase the loads, the car does go down.

Now when you roll the car, with zero droop, the roll center is at the contact patch for the inside tire and for the car to roll at all, the front must go down on both sides. In single wheel bump you still have the spring rate of the springs. Thus you can get a high roll rate without a correspondingly high single wheel roll rate. You will get this effect any time you run out of droop on the inside tire.

When I setup a car, I set the springs with no preload but the spring perches are touching the spring. The in this cars, droop is limited to the distance the spring is compressed to support the car. Either adding preload or setting the spring perch some distance from the spring will change handling. Whether or not the driver feels anything depends on all the other settings you have. But if you are close to the limits of performance, you will feel very small changes in things like preload. Preload in any amount will have an effect similar to a stiffer spring. Again you have to find the point at which preload has a noticeable effect.

I don't usually use preload but when I do, I have used adjustments as small as 1/6th of a turn on the spring perch to get the setup just right.

Most times, using the spring perch to set ride height won't have a noticeable affect. But I don't set ride height with the spring perches because when I do, I am making more than a simple ride height change. If you have a bell crank that has a variable motion ratio, you are again changing several variables when all you want to do is change ride height if you use the spring perches to change ride height.

A F1000 is a very high performance car. As such you need to really get to the top of your game when it comes to setups and tuning. These cars perform very close to Formula Atlantic or F3. Little things make very big differences.

[JJLudemann]

Droop limiting is very common...

At the top levels of racing, teams will setup dampers with springs so that they have a standard load at a certain length...

With an above ground front roll center..

you can get a high roll rate without a correspondingly high single wheel roll rate...

When I setup a car, I set the springs with no preload but the spring perches are touching the spring...

I don't usually use preload but when I do, I have used adjustments as small as 1/6th of a turn on the spring perch to get the setup just right...

I don't set ride height with the spring perches...

A F1000 is a very high performance car. As such you need to really get to the top of your game when it comes to setups and tuning. These cars perform very close to Formula Atlantic or F3. Little things make very big differences.

Thanks a lot for this explanation. It comes at just the right time, and I'm sure I'll refer back to it many times as I get closer to being on the track. Don't worry, I'm not underestimating the thought and precision that will go into getting a good suspension setup.

Along those lines, yesterday I met with the most famous race car driver in Thailand, trying to get him interested in helping test the car. He expressed concern about the control arms not having some sort of a weakened or flattened place near the base so that they break there during a crash rather than intruding into the cockpit. I've tried searching the Internet, but I can't figure out what he's talking about. He says all modern race cars in Europe have this. Does anybody have a hint?

-Jim

[provamo]

get another driver!

[Brett Lane]

Hey Jim,

Not 100% sure what you're getting at, but this protection is provided by the rod end. Being of a certain material with a known shear strength, in a crash the rod end should fail first.

[racerdad2]

Will anti-intrusion bars will alleviate his fears ? I like the other driver idea... Perhaps one of the hot shoes on Apex would enjoy a test driving vacation to Thailand ? :thumbup:

[R. Pare]

I think that he is speaking about the machined ends where a spherical is staked in in place of a rod end.

That type of end - at least every one that I've seen - are actually a LOT stronger than the usual 5/16 or 3/8 rod end shank.

[JJLudemann]

get another driver!

Heh, heh. I'd like to get this guy involved, though, as it would make the project much higher profile.

Hey Jim,

Not 100% sure what you're getting at, but this protection is provided by the rod end. Being of a certain material with a known shear strength, in a crash the rod end should fail first.

I tried to explain that we want the control arm to buckle in the middle rather than break at the base where it might intrude into the cockpit, but that didn't help.

Will anti-intrusion bars will alleviate his fears ? I like the other driver idea... Perhaps one of the hot shoes on Apex would enjoy a test driving vacation to Thailand ? :thumbup:

I showed him the anti-intrusion bars and explained how they work, but no joy.

I think that he is speaking about the machined ends where a spherical is staked in in place of a rod end.

That type of end - at least every one that I've seen - are actually a LOT stronger than the usual 5/16 or 3/8 rod end shank.

That could be it. Maybe he was saying they were stronger, not weaker. Thai is one of the hardest languages in the world to translate. Next time I can show him a photo of one of those and ask if that's what he's talking about. I was thinking maybe he misunderstood the purpose of the machined inserts that accept rod ends and go into the end of aero tubing. I have round tubing with round inserts. I'd be surprised if those aero-shaped tube inserts are intended to be sacrificial in a crash.

Thanks,

-Jim

[JJLudemann]

I see in one place the GCR defines a fuel cell as the bladder plus the metal enclosure, and then in another place states that there must be a metal bulkhead between the driver compartment and the compartment containing the fuel cell. Does this mean that, in an F1000 car where the driver is lying on the fuel cell, there must be two layers of metal between the driver and the bladder? How do current cars implement this?

Thanks,

-Jim

[Mike Devins]

One layer of .062 aluminum is sufficient.

In addition to that make sure that there is no sharp edges, that no dirt can get in between the cell and the enclosure and there is a way to get the cell out in order to inspect, maintain and/or replace.

[JJLudemann]

One layer of .062 aluminum is sufficient.

In addition to that make sure that there is no sharp edges, that no dirt can get in between the cell and the enclosure and there is a way to get the cell out in order to inspect, maintain and/or replace.

Thanks, Mike. Am I correct in assuming that it's OK to have to drill out about 80 rivets to access the fuel bladder? You only have to remove a single panel, and don't worry, one can't drill into the fuel bladder when drilling the rivets.

-Jim

[JJLudemann]

OK, next question: What's the maximum number of teeth I might ever want on the rear sprocket? I have a 2007 GSX-R1000 with the standard drive sprocket (17 teeth? It's hard to count) and currently have enough room for a 50-tooth rear sprocket. Is that enough for the short, twisty tracks in Thailand? It's certainly enough for the F1 track at Sepang, Malaysia, right?

Thanks,

-Jim

[ghickman]

50 tooth rear sprocket is fine, I highly doubt you'd ever need to use it unless you are running on something resembling a kart track. Then gear it to only use maybe 4th or 5th as your top gear.

Do you have the Excel Spread sheet that has the gear calculator vs speed for the GSXR1000 gearing? If not I can email it to you.

Jim you will also want to purchase 15 & 16 tooth primary sprockets. Those are the most commonly used.

[JJLudemann]

50 tooth rear sprocket is fine, I highly doubt you'd ever need to use it unless you are running on something resembling a kart track. Then gear it to only use maybe 4th or 5th as your top gear.

Do you have the Excel Spread sheet that has the gear calculator vs speed for the GSXR1000 gearing? If not I can email it to you.

Jim you will also want to purchase 15 & 16 tooth primary sprockets. Those are the most commonly used.

Thanks for the info. I don't have the GSXR1000 gear calculator. Could you email it to me at the same name as my ApexSpeed account at Yahoo.com? Are the 15 & 16-tooth sprockets a Suzuki part or custom made?

-Jim

[JJLudemann]

I was just re-reading the GCR (I know, I know, I should get out more) and it occurred to me that the height limit on "aerodynamic devices", rim height, must be one of those rules that the old hands just know how it's always been interpreted. I say this because it must not apply to rear wings, based on what I see racing. Or is there some other verbiage that countermands that? Is a windshield an aerodynamic device? A side pod? How about the whole body above the rims, because to an engineer that's certainly an aero device?

More importantly for me, would this rule mean that a symmetrical airfoil-shaped roll hoop fairing with a zero angle of attack would be illegal? Current plan was to make that out of fiberglass, but if I made it out of steel and welded it to the roll hoop does it become structural, and legal?

Also, what ever became of the forward-facing-gap controversy? Is a faired roll hoop a forward-facing gap? What about a rear wing supported by end plates, or a front wing supported by two pillars?

Sorry for all the questions. The answers may be obvious to people who've been SCCA racing for a while, but they're not to me.

Thanks,

-Jim

[S Lathrop]

That rule dates back to the days of "sports car noses", i.e. March and Ralt of the early '70's.

The rule was intended to keep people from enclosing the front wheels. If you made the track narrow enough, you could have a full fairing in front of the front tires.

A more fun debate might be about where the rules allow the nose of the car to be higher than the wheel rim forward of the front wheels. As I remember, the VDs were caught out on this issue until it was resolved.

[formulasuper]

......

....Sorry for all the questions. The answers may be obvious to people who've been SCCA racing for a while, but they're not to me.

Thanks,

-Jim

Trust me Jim, the answers are not obvious to a lot of us long time SCCA racers.

[R. Pare]

If I remember correctly, up until sometime in the early 90's, that particular rule stated "bodywork" instead of "aerodynamic devices", which is why you see the low footbox area bodywork on cars of that and earlier years. In '92 or so, the VD came over with the the first of the higher footbox area bodywork, and the rule was subsequently re-worded to accommodate them.

[JJLudemann]

I see belatedly that the same discussion is going on in another thread. The F1000 dimension table refers to the FC drawing, and on the FC drawing "dimension E" points only to the rim height from the front, but the FC table's text says "maximum height of any aerodynamic device forward of the front wheel axis". So that must by why I didn't think this was an issue until I panicked today .

But that still leaves the question of forward-facing gaps...

-Jim

[S Lathrop]

But that still leaves the question of forward-facing gaps...
-Jim

That is in the eye of the beholder. It has never been defined but has been fought over a lot.

[JJLudemann]

That is in the eye of the beholder. It has never been defined but has been fought over a lot.

Seems to me that someone should be able to read the rulebook and design a car with an almost certain chance of being legal. A rule that no one knows the meaning or purpose of makes that difficult. In my case, if I end up selling cars in Thailand, my Thai friends say they'd still want a prototype to pass SCCA homologation because Thai people don't trust Thai people. An SCCA homologation would be a reassurance that the car is considered safe and built to some set of international rules. To get a US homologation I'd have to ship a car to the US and back at great expense in time and money, or convince an SCCA inspector to come to Thailand for an all-expenses-paid vacation. And if the car is in the US and needs changing, it becomes a logistical nightmare.

Even for US racers, when someone builds a car and spends the substantial time and money required to get it to a race, if it fails inspection that will be a HUGE disappointment.

Does anybody have any idea what this rule is supposed to mean?

Thanks,

-Jim

[JJLudemann]

Things are moving along quickly now that I've found CNC and laser cutting shops that can do the work, and most of the design has been gone over with a fine-toothed comb. I'm actually using wrenches to install parts, although that's followed immediately by using wrenches to remove the parts. But at least the parts can be made to fit. Also, the body molds are finished. Yay!

-Jim

[Jnovak]

Seems to me that someone should be able to read the rulebook and design a car with an almost certain chance of being legal. A rule that no one knows the meaning or purpose of makes that difficult. In my case, if I end up selling cars in Thailand, my Thai friends say they'd still want a prototype to pass SCCA homologation because Thai people don't trust Thai people. An SCCA homologation would be a reassurance that the car is considered safe and built to some set of international rules. To get a US homologation I'd have to ship a car to the US and back at great expense in time and money, or convince an SCCA inspector to come to Thailand for an all-expenses-paid vacation. And if the car is in the US and needs changing, it becomes a logistical nightmare.

Even for US racers, when someone builds a car and spends the substantial time and money required to get it to a race, if it fails inspection that will be a HUGE disappointment.

Does anybody have any idea what this rule is supposed to mean?

Thanks,

-Jim

Jim, I have homologated lots of cars with the SCCA and it is not necessary that anyone actually inspect the car to get it homologated. Photos are acceptable. You may require an analysis document of a PE to sign off on your roll bar if it is of an "alternative design". The only time that an inspector needs to see the car is to get it inspected for a log book or at a race.

Now getting a log book is not the same as getting the homologation completed. A log book is required to race at an SCCA event. You will not need that in Thailand.

[S Lathrop]

The forward facing gap business goes back to the '70 and before. It was part of the body of rules that restricted or prevented the use of airfoils and other shapes to generate down force.

If a part has an obvious function other than creating down force, then you are legal. structures that are associated with the function of the engine are not subjected to this restriction.

The rules on roll bar fairings have recently been changed so that such a structure would not be considered a forward facing gap and therefore prohibited.