Double De' Clutch 101...

[Mopar92]

I had a conversation at the Glen with an ex 3 day grad and a newer driver of the series. Then, the discussion became 4 people large, etc. I just got an email from a historic racing guy I coach about it. So, I am going to put in my 2 cents about it. First of all, I do believe that there is a small misconception about what is really taking place inside the gearbox. We've all said it in short hand, but you are not JUST matching the rpm's of the engine and rear tire. You are matching the rpm's of the motor/new found lower gear set/rear tire. So, in other words, I do not believe that you are trying to match input shaft (connected to clutch/motor) and the output shaft. I believe that we are trying to match the actual gear meshing speeds. I am only talking very old style non synchronized and non dog ringed gearbox's. You literally have to come to a stop to get it in some gear if you do not match these speeds. I got to drive one of my Grandfathers 12 speed Freightliner when I was very young. It is a delicate procedure even with an 80,000 lb rig. He would demonstrate to us by shifting with his right hand holding a 1/2 full coffee cup, and bumping it with his wrist into the higher/lower gear without spilling a drop. Here are the steps again.

Full throttle, down the straight and into the brake zone, you do your version of threshold braking and then....
1-Brake
2-Clutch in
3-Bump to neutral
4-Clutch out (this has to take place to spin the input shaft!)
5-Blip 4,500-5,000 is a generic number and works very well in most boxes
6-Clutch back down/in
7-Downshift to lower gear
8-Clutch out
9-Start thinking about trail braking at this point
You Should have been on the brake the entire time of this downshift and even after it. A lot of guys will have the tendency to release the brake once the downshift is complete. You are not done braking. The tire wall does not care what gear the car is in! Use the brakes!


Here's the quicker version of what I just discussed. I am ok with teaching this to certain guys in the schools.

1-Brake
2-Bump (to neutral) You can easily bump it out of gear with 0 force.
You really need to time it just as you let off, and not after, because you will get some negative torque from the engine braking.
3-Blip
4-Clutch in
5-Downshift
6-Clutch out.
What we did here was save the step of wasting time with a clutch in/out just to get it to neutral. I believe this is a wasteful step. The reason I still had the "guy" use the clutch on the downshift is simple. We are still learning and there will be some messy downshifts and soft blips and the clutch will absorb some of the mistakes.

Full race "double clutch"-
1-Brake
2-Bump (to neutral)
3-Blip
4-Pause for 2 milliseconds ( I consider this a step in the downshift)
5-Stick it in lower gear.

You do NOT need to use the clutch to downshift a true non synchomesh or dog ring gear box. It is, however, a lot easier on the car if you use the clutch. A clutch is cheaper than a broken gearbox or worse, and over reved engine. The clutch just softens the mistakes. But the moral of the story is that you MUST blip the throttle with the box in neutral in order to internally match the gear set speeds.

Next, let me try to show you the difference between the gearbox's.
Fully Synchronized gearbox such as a modern day manual transmission. You could order a syncho gearbox in 1949 I believe in the US. It could have been earlier. I don't know.

1-The Dog ring gearbox. The dog rings engaged the gear set. When you hear that "Kapow" when you stick it into gear, and the whole car shakes, and the mechanics flip you off, this is what you are hearing, not the gear engagement itself. Can you see the little triangular pieces? Those are dogs. The driving shaft has an interlocking set that goes into those, hense turning the gear. I used Pegasus's pictures. Thanks Pegasus. One last word of advice. When you drive an RT 2000 car with our Sequential gear box, do NOT ever rev the motor to engage 1st or reverse gear. I don't need to point fingers, but if you guys want, come to grid just before a race, and I can show you how many people don't even know how to put a car into gear, much less shift properly. If you rev the motor and put it into gear to get it to mesh, you are a dog killer as Bruce MacInnes would say. We mean dog ring. If you can't get the car to go into neutral because the dog teeth are not lined up, simply let the car idle, pump the clutch once. Wait a second, and pull it back to first. It just needs to reshuffle the teeth. Please don't ever rev a car up to put it into gear. If you thought it was in gear, and the motor revved up, and it was not in gear, or even kicked out of gear, count to 5, and then pull back on the shifter. This could decide if you finish the race or take yourself out because of a poor 1st gear engagement.


Here is the dog ring that engages the gear. The shifting forks slide these dogs back and forth.










Synchronized gear set. The shift forks will slide the synchos, much like they slide the dog rings. Same concept.


You can see the little "mini gear" looking fingers. They will help start the meshing into the new gear be it up or down shifting. Even if the synchos are worn to death, meshing is still much easier because of the Helical cut to the gear teeth alone.

[Mopar92]

Just to make it very complicated, my 1951 Ford 8N tractor that I use is not synchonized and it does not have a dog ring either. It uses helical cut gears and YOU are the syncho. It is not designed to be shifted on the fly for that reason. However, I just had to... I hated slipping the clutch and starting it in 3rd or 4th gear. You double clutch upshift it, and double clutch down shift. However, one small issue... it's a hand throttle !

[GT-Subject]

Holy crap!!! I knew you weren't BS'ing me about two years of engineering school. Nice dicussion of the operation of a syncro and non-syncro tranny. By the way, nice tractor - we had one in the 50's - it was a great vehicle to learn the real meaning of double clutching. Although I did have quite a bit of trouble threshold braking the thing.

[Jim Pace]

Nice tractor!
Nice description of proper technique. If you learn to shift properly you can drive anything by modifying it slightly to fit that gearbox. Understanding WHY you are doing it is certainly part of the solution.

For years I had several WWII military trucks all non-synchro. Dbl clutch the upshift and dbl clutch w/ blip on the downshift.

Did I mention nice tractor?
JP

[badgersid]

you redneck sloping forehead close eyed mutant.did you have that written on your hand.

and i will say this again and again mel is a very very lucky girl. to have a really nice bright and good looking.

tractor

[Mopar92]

Thanks guys. Yeah, it breaks my heart to see a guy park a show room stock car or a Koni car because " the synchros are toast". To quote Stevie Dee , just "DTB", drive the *itch. Sometimes the synchro chews up a gear, but that is rare, they are only made of brass usually. Knowing the inner workings definately means knowing just about any car. Paul, the beauty of the tractor braking is that it has a lot of (only rear) brakes and turns in loose... IN addition to that, it has differential braking. I have mastered the bush hog. Go down, cut hard left, stomp left brake only, spins on left rear wheel, back to power and repeat until the grass is cut. It's a redneck 0 turn mower. The little Ford 8N is a real joy to ride, much less work with. It is a real work horse. My next door neighbor bought some new little $20,000 2 cylinder diesel and he laughed at my 8N. That was until I pulled his butt out of a ditch! Earlier in the year, a giant hay farm down the road bought a huge dually tractor that was over $120,000 with XM radio and all that. He broke down in front of the house. Some computer shut down it's auto shuttle shift. So, the little 8N fired up in 30 degree weather and I towed him back, although it was working hard and only in 1st gear.... Yeah, I have pulled 2 John Duuueeer's home! 1951 Baby....

[LimeRockRacer]

How about a Tractor Pull Memorial?

[ORBlues]

>>Thanks guys. Yeah, it breaks my heart to see a guy park a show room stock car or a Koni car because " the synchros are toast". To quote Stevie Dee , just "DTB", drive the *itch. Sometimes the synchro chews up a gear, but that is rare, they are only made of brass usually.<<

Not sure if you are being too hard on guys with sychros. Once the friction surface is gone (which does the synchonization rather than the blip) you need to treat it like a non-synchro, but with a much smaller margin of error. The teeth are so fine it can seem almost impossible and once the teeth are damaged it is all over. Even if dog rings are rounded off, you might be able to keep going by holding it in gear - sometimes.....

Of course if you double clutch with a syncho box it they will last almost forever as you take most of the load off the friction surfaces.

ChrisZ

[Yarab]

You must be a mind reader I just pulled out all my books last night to make sure my sequencing was right during my shifting. I reviewed all of the info you presented above, but it took the engineering and driving gods about 45 pages of confusing mumbojumbo to describe it. I like the 3 paragraphs much better. After you have 2 997's blow up on you, you start thinking it is you.

I thought that was a Hoyt-Klagwell.

Thanks

Ron

[cdh]

good stuff Duke, really need to see a pic of the 8N towing your civil war cannon

[Rosso]

WOW Keith! That's a great piece of technical writing on a subject (gearbox internals) that is almost universally misunderstood. Can you explain women next?

[5&counting]

Keith,

What about:
Brake
Clutch in
Huge Throttle and of course some brake
Downshift
Clutch out
POWER

[Slowhands]

Originally Posted by Mopar92

Here's the quicker version of what I just discussed. I am ok with teaching this to certain guys in the schools.

1-Brake
2-Bump (to neutral) You can easily bump it out of gear with 0 force.
You really need to time it just as you let off, and not after, because you will get some negative torque from the engine braking.
3-Blip
4-Clutch in
5-Downshift
6-Clutch out.

Keith,
Question: as you let off what? The gas? If so, does this mean you actually have to bump it AS you are going to the brake and not AFTER?

[Mopar92]

Harsha, I brake and bump it to neutral at the same time, otherwise it is a little more pressure to get it out of the gear and into Neutral. Because the engine is providing torque on the gears from decelleration. It prolly' wont hurt anything, but the least resistance, the better I think. Matt Franc, you are single clutching you rat *astard.... Works, but then again, you don't have to fix them at night... PS, I need a dimmer switch for a 1967 Dodge Dart...get me one....

[Mopar92]

Originally Posted by cdh

good stuff Duke, really need to see a pic of the 8N towing your civil war cannon

Doug.... Here... you know what you are doing.. use your imagination.

[dalyduo]

What a great thread.

[John Greist]

And the school cars with the Hewland 4 speeds will teach it all - to those able to learn.

[GEORGE]

If any of the School cars came up for sale I would buy one. I really loved the technique of a true Manual box.
I would not be interested in the R/T 2000 though.

[John Greist]

Originally Posted by GEORGE

If any of the School cars came up for sale I would buy one. I really loved the technique of a true Manual box.
I would not be interested in the R/T 2000 though.

You'll have to get in line behind Revere and me. We both want one and I've spoken with Todd. Shifting and slip angles as well. When the new car arrives....

[dalyduo]

I would guess there will be an RT with a Mazda motor in it way before there will be an all new race series car... Which means your school car purchase may be quite a ways off.
Had a chance to fling one of the school cars around the upper autocross at LRP a few weeks ago... Good fun.

Originally Posted by John Greist

You'll have to get in line behind Revere and me. We both want one and I've spoken with Todd. Shifting and slip angles as well. When the new car arrives....

[rslonaker]

Originally Posted by GEORGE

If any of the School cars came up for sale I would buy one. I really loved the technique of a true Manual box.
I would not be interested in the R/T 2000 though.

It is called a Crossle 35. Club Ford in SCCA world. Usually in the $10k-17k range. At least the last time I checked. GREAT CARS.

[John Greist]

Just look at Rob's slip angle. What fun!

DD. Sometime, SBR will run through the Neon crate engines they had when the Mazda deal was done so the swap will be coming. That change will start TJR threads buzzing as there will likely be teething problems as there were when the Dodge engines replaced the Fords. Maybe the CG will go down toward Ford level with attendant effects on handling which would prompt changes in springs/dampers, etc. Interesting time when engineers and testers have fun and sentient customers follow the process with interest or angst.

[dalyduo]

Agree on all counts Dr...

Most of the RT teething had been done when I showed up five years ago. The change from Michelin to BF Goodrich brand tires took over a year to sort out. The appearance of the all purpose G-Force tire and the Hansford device really put the fun back in the series. The G-Force street tire was in many circumstances faster than the hockey puck slicks it replaced and a terrific rain tire as well. The Hansford made subtle car differences less meaningful and costly to racers. After the hamster device appeared you heard much less griping about cars not being equalized.

SBRS has the world market pretty much cornered on all things Neon engine related. In a few cases they may be the only source for things like heads and engine contoller chips. Apparently there may be enough inventory to run another couple of years.

You'd hope they'd use that lead time to properly sort out the Mazda engine install. Certainly in their best interest to do so for both the sponsor and the customer. In the end we'll all get to be testers but giving Jason, RB, MHP, JP, Rob and the other instructors who know the difference a chance to sort it would really improve the quality of the experience.

Originally Posted by John Greist

Just look at Rob's slip angle. What fun!

DD. Sometime, SBR will run through the Neon crate engines they had when the Mazda deal was done so the swap will be coming. That change will start TJR threads buzzing as there will likely be teething problems as there were when the Dodge engines replaced the Fords. Maybe the CG will go down toward Ford level with attendant effects on handling which would prompt changes in springs/dampers, etc. Interesting time when engineers and testers have fun and sentient customers follow the process with interest or angst.

[John Greist]

DD,

I was back a car generation in 1995, when SBR went from Ford to Dodge engines in the Formula cars, presently used for schools. We raced them until the RTs came along in 2000 and that transition was easier. After Ford to Dodge, the extra power in unrestricted cars had JP and Barry Waddel lifting before the Kink. I have video of them running together which was glorious. It was heart stopping to see JP with oversteer in the Kink, quickly flicking it away and checking his watch a few seconds later at the flag station heading to Canada.

The brakes proved inadequate for the greater weight and higher speed and they literally had 90 degree gutter pipe ducting air to the fronts which still wasn't enough. While the rotors obviously cooled between 8 and Canada, the fluid could boil at 8 and you'd find no pedal at Canada, so in sequential races, Revere ended on the tires across the gravel at Canada and I in the gravel. This was late race in both cases, so hard to anticipate - learned about testing the pedal on straights.

Lou Dagastino came in and with the testers you listed, dealt with the Neon's higher CG and other issues caused by the engine swap and made the Formula car a gem. With restriction and other changes, JP could say at the Kink on van arounds , "The car will do it," and after lots of incremental work, Revere and I got flat through the Kink. Still more fun to go flat in a Formula car there than an RT or even FC.

It wouldn't surprise me that SBR'll work on a Mazda engined car and take it to all the tracks to find the wrinkles we all know are lurking, waiting to be found. At least I bet the testers would like to be developing the car with the Mazda engine as well as the Mazda decal.

[Mopar92]

Wait just a minute.... the first right of refusal is as follows...
John, Revere, Keith...

[John Greist]

Originally Posted by Mopar92

Wait just a minute.... the first right of refusal is as follows...
John, Revere, Keith...

Right you are, as always...

[Mopar92]

What is interesting is that the folks that say you dont need to double clutch that 4 speed are right. You don't need to, but when you do, it sure goes in with no click... nice and sweet.....

[Rosso]

Originally Posted by Mopar92

Wait just a minute.... the first right of refusal is as follows...
John, Revere, Keith...

LOL - If it were only so simple as just buying the car. Two years ago I met a guy that lives up the street at a neighborhood holiday cocktail party. Said he was going to do the 3-day school at Daytona in January or February. Told him he would have the most fun he would ever have in a car with his clothes on. He did. Got hooked. Bought a vintage racer of some MG or TR description. Fun, but not competitive and fragile, blew up a couple of motors. Not fun to blow up. Bought a vintage sports racer with a "real" race motor. Now competitive and durable. Fast forward to last month - now relatively inexpensive vintage sports racer sits in a fully stocked 30-foot double deck trailer painted to match the humungous Prevost motor home he bought to tow the lot. But he's only spent $15,000 on the race car!!??

[dalyduo]

What do you expect from a guy who lives at a coctail party.

In the end I suppose it's whatever you have to do to feel like you're at the party, so to speak. For what he's spending on a trailer and motor home he could run a few skippy seasons, learn a slew of new tracks and really sharpen his driving skills. But if I didn't have all the good Skippy instructor feedback, comaraderie and skill building I'd want a Prevost too!

Originally Posted by Rosso

Two years ago I met a guy that lives up the street at a neighborhood holiday cocktail party. Said he was going to do the 3-day school at Daytona in January or February. Told him he would have the most fun he would ever have in a car with his clothes on. He did. Got hooked. Bought a vintage racer of some MG or TR description. Fun, but not competitive and fragile, blew up a couple of motors. Not fun to blow up. Bought a vintage sports racer with a "real" race motor. Now competitive and durable. Fast forward to last month - now relatively inexpensive vintage sports racer sits in a fully stocked 30-foot double deck trailer painted to match the humungous Prevost motor home he bought to tow the lot. But he's only spent $15,000 on the race car!!??

[John Greist]

Originally Posted by dalyduo

What do you expect from a guy who lives at a coctail party.

In the end I suppose it's whatever you have to do to feel like you're at the party, so to speak. For what he's spending on a trailer and motor home he could run a few skippy seasons, learn a slew of new tracks and really sharpen his driving skills. But if I didn't have all the good Skippy instructor feedback, comaraderie and skill building I'd want a Prevost too!

For many, it's as much the fun of the scene as performance in the car and that's true at all levels of racing. What's really fun, is winning at the scene and before winning, all the years learning how to win from the great folks at SBR. Fun is fun, but keeping the focus on learning more is the best fun I've had and am having now in FCs.

[John Greist]

Originally Posted by Mopar92

What is interesting is that the folks that say you dont need to double clutch that 4 speed are right. You don't need to, but when you do, it sure goes in with no click... nice and sweet.....

With all the time one has in the brake zone, why not double clutch even the sequential to gentle the box a little? What scum bag doesn't double clutch - OOPS - except between 10 and 11 at Mt. Tremblant... Guilty as charged

[Rosso]

Originally Posted by dalyduo

What do you expect from a guy who lives at a coctail party.

In the end I suppose it's whatever you have to do to feel like you're at the party, so to speak. For what he's spending on a trailer and motor home he could run a few skippy seasons, learn a slew of new tracks and really sharpen his driving skills. But if I didn't have all the good Skippy instructor feedback, comaraderie and skill building I'd want a Prevost too!

Hey, I've lived WORSE places! None the less, an unfortunate choice of sentence structure, eh?

But, I have always said that if not for the steady, moderating influence of my lovely CPA wife, I would probably live in a cave (or a neighborhood bar - and not in the current neighborhood) and spend every nickel on race cars.

[Slowhands]

Originally Posted by John Greist

With all the time one has in the brake zone, why not double clutch even the sequential to gentle the box a little?

Correct me if I'm wrong, but I think the double clutch is only effective for boxes you can slip into neutral between gears to spin up the output shaft.

Originally Posted by Rosso

Hey, I've lived WORSE places! None the less, an unfortunate choice of sentence structure, eh?

No, Thurber would call that a SUPERB choice of structure. You don't appreciate your own literary gifts.

But, I have always said that if not for the steady, moderating influence of my lovely CPA wife, I would probably live in a cave (or a neighborhood bar - and not in the current neighborhood) and spend every nickel on race cars.

And what, may I ask, is wrong with that?

[dalyduo]

John,
Don't know anyone going through life with more joyful wise awareness of the process than you while dragging Revere along by the ear as well. Youth is wasted on the young because they usually don't how to evaluate and enjoy the journey. From where I sit you're an inspirational vibrant prototype of a life well lived with a lot more to enjoy!

Originally Posted by John Greist

For many, it's as much the fun of the scene as performance in the car and that's true at all levels of racing. What's really fun, is winning at the scene and before winning, all the years learning how to win from the great folks at SBR. Fun is fun, but keeping the focus on learning more is the best fun I've had and am having now in FCs.