JF2 Build

[formulasuper]

How's the new JF2 coming along Jerry? Any photos? Or is it being built in your super secret skunkworks?!

[jerry freeman]

The JF2 is almost off the jig. I will start a build thread shortly when there is a little more to see. It's going ok but never fast enough. Work is picking up a little so I should be able to buy parts a little quicker. There should be a preview of the unfinished cad model.

Scott the only thing super secret about my shop is how much money the wife knows I'm spending.

Jerry

[RussMcB]

Jerry, that looks fantastic!

Do I see you've been influenced by the Phoenix F1K.10? Your sidepods remind me of that car.

The only thing I'd like to see is rounder transitions in the engine cover area. Of course, that's a lot easier for me to type than for you to build. :-).

[jerry freeman]

Yea Russ, I plan on buying the side pods, undertray, and diffuser from Dustin at Phoenix. It won't have the chimneys though.

The cad model is not finished. Mainly the body part. That's the hardest part for me to draw. This car will have rounded edges and smother transitions.

I need to get the build thread going I guess so we can move out of the classifieds.

Jerry

[-pru-]

I need to get the build thread going I guess so we can move out of the classifieds.

[jerry freeman]

Here's the first look. It still needs to be flipped around to finish welding and it has some rust that needs to be cleaned up. Overlooking that, let the criticisim start. That's how I learn and make improvements. I'll add some info as I go. Time for some sleep.

Jerry

[Christopher Crowe]

-- congratulations on completion of chassis number 2! This JF chassis clearly has to be stiff as hell. What does she presently weigh?

Congrats on completing this very tough part of the process!

Chris Crowe

[jerry freeman]

When I get the motor out I will weigh the bare frame. Unfortunately I never weighed the first chassis to compare.

It's stiff, I just hope the frontend is stiff enough.

Jerry

[billwald]

Excellent looking work Jerry! The JF2 looks awesome. Bring it south sometime.

Is JF short for Jet Fighter?

[jerry freeman]

Thanks Bill. There's nothing that resembles a jet fighter outside Redstone Arsenol in Huntsville, AL.

The JF stands for (just fu..ed). Story of my life. Doesn't stop me though. If I want to keep froom going back to driver school I will have to go south in Jan. Something I've wanted to do for a few years now. Working hard on it. Work sucks and I need $6000 quick. We'll see.

Jerry

[jerry freeman]

It's moving at a snails pace but there is progress. The first corner is tached and being checked and measured. Cad model and real life aren't always the same. Got the a-arm fixtures built also so I can build at will. Hopefully I want need to many corners.

For those that are still wondering what the hell kind of front end is that just google F1 V-Keel front suspension. It was on the '05,'06,'07 Renault and the '07 Red Bull.(unless I missread the info) The '05 and '06 Renault were obviously constructor and driver world champions.

The goal is to combine the best mechanical grip (like the Citation) with the raised nose best aerodynamics to get the Alabama A.. Kicker. Just need to find a driver with those large attachments. If you can't tell I'm excited about the new car even though it's not even rolling yet. Back to work.

Jerry

[jerry freeman]

Finally got the motor out of the chassis and weighed the bare frame. It's 145 pounds without the steel belly pan I will weld on. Anybody want to give the bare weight of other bare frames?

Jerry

[JohnPaul]

Check this out there is some info:

http://www.apexspeed.com/forums/showthread.php?t=45143

[jerry freeman]

Thanks JP.

I have a sherman tank as usual.

Jerry

[R. Pare]

Jerry:

I hope that the rear leg of the front lower a-arm is just a mock-up piece - we found that braking loads are high enough (on the FC, and the FB loads are higher) to have to increase the strength of that leg substantially.

[ASRF1000]

Jerry,

With the steering rack positioned that low and that far forward, will the steering shaft interfere with left foot braking? Just something that stood out to me.

Looks great! Keep up the good work!!!

[Christopher Crowe]

-- the most loaded arm in the car! Does anyone know (by real measure, not just the theoretical) how much load is going through that tube and pick-up point? I mean with all road undulations and the curb-hitting all in. Wonder if there's ever been a load-cell device used to get a real measure...

Hey, and the car's coming together, JF; like the raised-nose and keel system. One of these days, someone's going to really maximise the use of under car air by way of a high nose, I would think. Good luck with her!

[jerry freeman]

Richard,

That is the real a-arms. The rear bottom tube is 7/8 X .065 round 4130 chrome moly. Please let me know what you think it should be.

Jon,

The steering rod column runs along the floor between your feet just behind your heels and then turns up to the column at the steering wheel. You can left or right foot brake. I right foot brake but want to start getting better at the left foot. Until I get some kind of assisted shifter I will keep using the clutch on downshifts.

Jerry

[S Lathrop]

Jerry

Look at the table ttp://www.aircraftspruce.com/catalog/mepages/4130streamline.php.

I can tell you that the 1.349x.571 is not strong enough for the lower a-arm on my FC. We had to increase the tube size when we increased the front track to the maximum allowed. Look at the round tube equivalent numbers. You do not gain a lot of strength from using .065 vs. .049. You do gain a lot of weight.

We use .049 throughout the chassis and suspension except where rules require more or we have a special situation.

When our design was adapted to school cars, we built the lower control arms from 1" round tubing.

You are building a car that might see over 3Gs in cornering and braking loads. The recent versions of Mitchell software will calculate the loads on the suspension links.

[R. Pare]

Jerry:

Your worst loading will be under braking (I think, or a combination of braking and cornering), and you should be able to calculate the loads relatively easily. Rough tracks make it even worse, of course.

I guarantee that your 7/8" tube will bend real fast, especially with it as long as it is - the longer they are, the bigger a cross-section it needs to resist buckling.

Also, the upper ball joint rod end needs to be at least 1/2" (can't tell what size it is in that pic), with as little thread as possible exposed or it will also bend under braking - we've even seen FFs bend them when 1/2" of thread was exposed, so it wouldn't surprise me on an FB, if even a 1/2" joint is close to being borderline.

I'd hate to hear that you trashed all this work on it's maiden voyage!

[jerry freeman]

Richard,

The top rod end is 1/2 in and I definately try to keep the threads screwed in all the way and use shims to adjust the camber. I used this and 3/4 rod ends on the bottom of my first car. I have spherical joints on the bottom of this one. The old car took a pretty hard hit straight into the left front and didn't break any rod ends. I have 3/8 at the pickup points. Bent some but no breaks. Doesn't mean it won't happen though. This car will "HOPEFULLY" be faster and brake harder than the last one so I'm back to redesigning the bottom front a arms. Thanks Steve and Richard.

PS. In the future tell me these things before I finish welding them. JK.

Jerry

[R. Pare]

Guess that I will have to renew my license for my crystal ball after all!

Upper a-arm inner joints can probably be 5/16 Aurora MM series - helps keep from tearing up pickup points in a crash. The upper a-arm doesn't see as heavy load as the lower in cornering, except for the forward link under braking (compression again), but the link is a lot shorter than the lower rear, so it cannot buckle as easily.

[john f]

Take a look at this:

http://www.engineersedge.com/column_...lumn_ideal.htm

Might help you size your arms.

john f

[jerry freeman]

Had a few people ask about the car so I thought I would try to post some pics of the SLOW progress. Thought I would be alot farther along by now. Typical story, got time and no money or got money and no time. Such is life. It is a roller though. I'm thinking about putting a 2 x 4 in it for a scrub brake so I can have the daughter push start me down a hill just to drive it. I need to get back to the track.

Jerry

[JohnPaul]

Great job Jerry. I wish i had a 1000th of your talent.

[jerry freeman]

Great job Jerry. I wish i had a 1000th of your talent.

JP, that and a couple dollars will get you a bad cup of coffee. Or broke and miserable. I obviously don't like coffee.

Jerry

[Rick Ross]

Nice work, Jerry.

[Christopher Crowe]

A real progression from the JF-1, I think. I don't think people realize the massive amount of work that goes into design and construction of a race car. Or, you could say it's easy. Like building a model car kit... with no directions and no parts!

Congrats on Number 2!

[carnut169]

Looking good Jerry!

[glenn cooper]

The dude has skills. Mad skills...

[S Lathrop]

Just a little detail for you to consider when you do the front wing.

I build my front wings with 3 ribs per side, an inner or mounting rib, middle and end rib. I run the spar between the 2 middle ribs. The idea is to have the first failure point of the front wing at the middle rib on either side. If you run the spar to the end rib, the first failure point will be at the inner rib. In minor impacts you only loose 1/4 of the front wing vs 1/2.

[jerry freeman]

Steve,

I read where you said that in another post a little while back but I had already made what you see now. I completely agree with you. I destructively tested the design I have now at Barber and it did exactly what you said.

Problem is, I'm affraid to build a wing like that because I'm going to put the winglets(second element) on it and I don't want it to collapse at the end of the back straight at Road Atlanta. If I was an engineer or had access to FEA I would be willing to do that because I would have confidence in it. I have confidence in what I build now because I know it will work. I bought a wing once when I was building super comp dragsters that didn't have a spar tube in it and it collapsed on my customer at 140 mph. He wasn't very happy even though I replaced it for free.

Any pointers on how to do it would be much appreaciated. And no I'm not going to buy an expensive one when I can build one for $100 for those who were going to suggest that.

Jerry

[S Lathrop]

I use a spar of 1.125 .050 4130. My flaps are 11 inches wide, 8" cord. on a wing that has an 11" cord. No problems at all. My wing skins are .032 6061 T6 so nothing special there either. I do have the bracket for the flap aligned with the middle rib.

I would guess that the max down force you will see is 250 lbs. Try using sand bags to test the wing.

[jerry freeman]

Thanks Steve. One day I would really like to talk to you in person.

Jerry