Technical 'stuff' - for those what asked :-)

[BB-Q]

Well, ok- I'll go first.

I found that very interesting- but I'm amazed at how basic it is.

[Ian7]

Yes I enjoyed that,a good read,... I`ve been a mechanic for 37 years and its a job your always learning, you never know it all and I still enjoy it although the electronic technology on todays cars is getting the better of me.
I used to visit the Pod back in the late 70`s and then other things took over my life and I finally came back about 2 years ago (a very long break), lured back by the top fuellers my interest has grown to all the other classes as well, its taking a while to understand them all but I`m getting there.I`ve been able to find out a lot about fuel engines, which really interest me, and by the wonders of the internet its become possible, we never had that before, straight from people who know what they are talking about,so thanks to you guys for filling in the finer details with excellent stuff like this.
Now, clutches, thats a real grey area for me, so any info on them would be great, TF clutches, how do they work? what is a clutch cannon?
Regards,
Ian

[BB-Q]

Ian7 said:

Now, clutches, thats a real grey area for me, so any info on them would be great, TF clutches, how do they work?

Black magic.

They've all sold their souls to Santa!

Hope that helps

[Tet]

Ian7 said:

Now, clutches, thats a real grey area for me, so any info on them would be great, TF clutches, how do they work? what is a clutch cannon?

Clutches on a top fuel car are no different to a multi-plate clutch on a road car in principle -- alternating discs and floaters, providing friction over a large contact area. Push the discs/floaters together and the friction increases, thus locking the clutch up. Allow them a bit more freedom to move and you slip the clutch. But where a road car has a pedal activated clutch, the clutch on a modern fuel car is activated by timers, preset by the tuner before the run. The clutch itself is centrifugal. The cannon is simply a hydraulic ram that physically prevents the clutch fingers from flying out and fully engaging the clutch.

When you hear about people tuning a fuel car, most of what they're doing is configuring how the cannon moves during the run. That in turn controls how much the clutch locks up. The aim is to keep the car right on the limit of traction. Lock the clutch up too soon, and you overpower the track. Lock the clutch up too slowly and you run the risk of not providing enough load for the nitro to burn. Remember that in a modern fuel car, there is no gearbox, it's simply direct drive to the rear wheels, via the clutch. In a methanol car, the driver can short shift if things aren't going to plan. In a fuel car, the driver is much more at the mercy of the settings put into the car by the tuner, and has correspondingly less control over the car during the run.

That should do as a brief overview. I'm sure Cliff or Peter can provide more details if necessary.

[BB-Q]

Ok, so that explains things pretty well.

Can we then view the cannon as a type of hydraulic release bearing, that has a timed release?

And how is the clutch locked up/not set off during the burnout?

Unfortunately/fortunately (depending on your point of view) this is one of those subjects in that each answer usually brings up another question. Still, I can think of much worse subjects to discuss!

[Ian7]

Thanks for that, all becomes clear now, so when the crew guy flicks a switch in front of the steering wheel just before pre stage is he activating the timers? also something is pulled out from the throttle linkage area up by the hat, is that the throttle stop?

[Tet]

Ian7 said:

Thanks for that, all becomes clear now, so when the crew guy flicks a switch in front of the steering wheel just before pre stage is he activating the timers? also something is pulled out from the throttle linkage area up by the hat, is that the throttle stop?

The switch is probably to turn the datalogger on. Although the current range of dataloggers have storage to spare, the previous generation used to have much less, and if they were switched on before the burnout, they would fill up their storage before the run itself. Hilarity ensured when on some cars the datalogger switch was placed next to the kill switch... mentioning no names, of course :-)

The timers are usually activated by a switch under the throttle pedal. When the driver's foot is flat to the floor, the switch starts the timers running. The bit being pulled out of the throttle linkage by the hat is indeed the throttle stop. It's an incredibly high tech device -- just a simple rolled pin or similar that physically prevents the throttle from being fully opened. That means the pedal doesn't reach the floor, so the timers aren't activated on the burnout. After the car has backed up from the burnout, the crew chief removes the stop, and takes the car to the line, fully armed and ready to go. When the tree runs, the driver hits the loud pedal, the switch starts the timers, and if the crew chief has got it right, 4 and a bit seconds later, the car's crossing the line at 300mph+

[Nitrohaulic]

I'm still getting my mind acclimated to the world of blown nitro (nostalgia funny in progress that some here know about) and will pass along a thought or two that Frank Oglesby posted for us on classicfunnycarboard.

It has to do with burnouts but, the pedalfest mention above made me think about it. Frank explained to us how a barrel valve is made for idle or wide open throttle and nothing in between. He said his car broke after a burnout and he almost didn't tear the engine down, then he was glad he did because he found warped valve reliefs smiling up at him. He figured out that a lot blown up engines during runs were set up for it on the burnout, and told us to NEVER let the engine labor at part throttle as the tires dry off and start to pull at the end of a burnout (like you wouldn't hesitate to do with a bracket car). He said you'll kill your engine right then, even if it doesn't show up right then.

Makes sense if you think about it. If the barrel valve is half closed, it's not like half the amount of air is coming in because the butterflies are only half open! I don't think they do much restricting on a blown engine until almost closed. You've pretty much got half fuel and full air. Add load? LOL.

He also wrote about designing the throttle pedal so that the pivot point is about 25/75 under your heel if you want to really be able to control your burnouts. Rotate your foot instead of moving your leg.

Great to see how your car's coming along. From what I read on your other thread, your money went the opposite direction that ours did this year! Last year I accumulated a rolling chassis, a Lencodrive, blower, billet crank, and BME rods (all used except the last two, and those were second hand deals). This year it's been a starter, pair of valve covers, and a Promag! It's like we've mirrored each other. I started out strong, then slowed down.

Still like to check in here and see how you folks are doing now and then. ( Translated, keep an eye on you! )

[Furyous]

Thanks Jon, I think I was one of the of the original posters after tech stuff.

That does all look quite straight forward once its explained in laymans terms.

[Benni]

Hi John (and others in the know) :
what is "backsiding a piston" ?
Regards,
Benni

[MotorPsycho]

a good thread on classicfunnycarboard about burning and backsiding pistons

http://www.classicfunnycarboard.com/cgi-bin/ikonbo...