What's the guy with so many of you lot driving autos?! =P

[OSL-060]

Plus it sounds cool

I'll admit to blipping downshifts just for onlookers benefit in an injected 304
I love bikes for the same reason too, 2 stroke 250's like the RGV's, such a sweet sound on the downshift...and that lovely 2 stroke smell.

 

[mixin]

Great Post Mixin, it's explained really well. But I've got one question, isn't the process during the downshift actually referred to as 'Double De-Clutching'?

I've never heard it referred to as that. To declutch is to disengage something, so for every declutch action you would need a clutch action -ie the pressure plate pushing the driven plate against the flywheel & pressure plate facings.

And even with the older straight cut gears no blipping/rev matching is required on the upshift. Simply clutch in> neutral> clutch out>clutch in>upshift>back on the throttle. Maybe you meant this anyway and I'm reading it wrong.

Bevel cut gears came into chevs in 1929 - making them far easier to drive, and upshifting became easier, but it was only an interim measure until synchros on 2nd & top (3 speed) were introduced in the early 30s.
To drive a '28 chev you actually need to double clutch it on the way up too - which sounds the opposite of what needs to happen.
However, the layshaft in vintage gearboxes slows down so quickly, that even when going up a gear, the shaft has slowed way too far to allow the next gear to slip in. Thus you need to let the clutch out in neutral, give it a rev to speed up the layshaft, then push the clutch back in & grab the next gear, then release the clutch.
If you grind them, you'll never get it in!

I think you are confusing straight & bevel gears with straight & helical teeth - the 2 most commonly used modern designs.
Helical teeth eliminate the whine you get with a straight cut gear, and are used in all forward gears in modern cars, while straight cut gears are usually found in reverse - but these are bevelled to allow easier shifting!

Straight sided gears are not like a "straight cut" gear as found in a racing box - straight sided gears are gears where the teeth are the same shape right to the edge - meaning the side of the gear still has the full profile of tooth exposed.
Bevel-cut gears have the end of each tooth machined into a taper to alliw it to slip in easier - this taper looks like the taper on a synchro ring.

In the older boxes, the actual gear slid along a shaft & the outside teeth of the gear engaged & disengaged.

In the 30s, the more modern design was introduced where the gears are in constant mesh with the external teeth, and internal teeth actually lock on & off the mainshaft to transmit drive. This is one reason why synchro boxes are so much easier to drive.

As for Heel and Toe or what it really is 'toe and heel'... I wouldn't say it originated as a separate shifting method. It's simply double declutching with a more precise rev match over the blipping technique.

Heel & toeing was essential in racing in the 40s & 50s, and was even essential until the early 70s in Australian touring cars.
It wasn't until the mid/late 70s that non-synchro boxes finally died a long & painful death!

For those who seem confused, it refers to you toe being used on the brake pedal to slow down, while you angle your heel out to blip the throttle whilst maintaining consistent braking. It can be difficult to master - especially in a stock commodore - the pedal spacing isn't real good.

Most of the wanker "heel toeing" I see on the streets today isn't even done properly - heel toeing refers to using all 3 pedals at once.

Too many ricers I see think they are cool by pretending to heel toe.
You hear the blip & downshift out of them, but when you don't see no brake lights, then you know they are wanking themselves!!!

 

[Bec]

Double-clutching an old vehicle needs rev matching when the gears are in compression for it to be smooth (well sort of...there was nothing really smooth about the old truck I drove for a while :b: )

I don't use heel toe, as I only rev match when I need to downshift up a hill. This keeps the smoothness and power up to it nicely. I really don't see a reason to use it any other time (other than the racetrack, or a sweet sounding car purely for other's enjoyment). It's just a waste of energy

 

[OSL-060]

Thanks Mixin, yet another interesting post Being more than 50 years before my time I was confusing bevel cut with the straight cut gears which I knew a little of, you learn something new everyday. Imagine having to drive a vintage beast everyday, with bi monthly clutch cable lubrication from so much bloody use. You'd have a monster left leg too

 

[mixin]

Can you imagine having to oil your rocker gear every morning & wind the crankhandle over?

 

[davo]

who the hell thinks clutch in blipping the throttle and clutch out is double clutching

tomate-o, tomar-to. i used the wrong term, sorry.

yes really its only single clutching... ive just always called it double clutching for some reason.

I have driven fire trucks with non syncro box's, that is when you do the real double clutching.

I dont even think about it when i drive a manual these days, its just the automatic reaction.

Like i said before, i get these habits from riding the bike, where if you dont blip every downshift, you have a very dissapointing ride.

 

[jetspin_vn]

To heel toe correctly, one must double clutch whilst under brakes. Left foot is used for clutch, while the right is braking and throttling AT THE SAME TIME. (for the blip and re-engagment)

It takes literally months of untidy shift work and inaccurate brake pressure to master. Don't believe anyone who tells you its easy because its not.

I can do it, but only because I took the time to learn it.

EDIT / DISCLAIMER: Even then, it only really comes into play when your racing up to corners with the intention of coming out with the throttle firewalled, which on public roads you shouldn't be doing anyway.

 

[Torana]

Then your in the same gear throuought the entire corner, and power out of first shift to second (without the clutch if your good ).

Do you mean to change gears without using the clutch?! Even if the car's off and you're just palyin' 'round with the gearstick, you should ALWAYS use the clutch. I'll use the clutch ALWAYS 'cause I like money and I don't like costly repairs. Just my thoughts...

 

[mixin]

To heel toe correctly, one must double clutch whilst under brakes.

Err, no....
In a car with a synchro box (no commodores were ever made without them on all forward gears), you only single clutch & blip the throttle to raise the revs to match the next gear. There is no need to double clutch as the synchros take care of the shaft speed matching.

Blipping the throttle on a downshift only raises the RPM to prevent the compression lurch upon releasing the clutch - that is all that is needed to make for a smooth drive in any manual commodore, and minimise wear.

In a racing situation, the transfer of weight off the rear wheels means compression lock is a real danger when downshifting under brakes - thus it is essential to heel toe.

That is the essence of heel-toeing in a car with a synchro box.

Not even the V8 supercars double clutch, they simply heel toe to match the RPM & road speed - and they have no synchros, but it's a dog engagement box does work differently.....


If you have pulled down a few manual boxes & replaced synchros, you will understand exactly how they work & why doubleclutching - as opposed to heel toeing, is not necessary.

 

[Bec]

Do you mean to change gears without using the clutch?! Even if the car's off and you're just palyin' 'round with the gearstick, you should ALWAYS use the clutch. I'll use the clutch ALWAYS 'cause I like money and I don't like costly repairs. Just my thoughts...

I drove my VC for ages with minimal clutch use. The clutch plate and cable were stuffed - it had just enough to not stall at a stop. I had to tighten the cable every couple of days.
I would only use the clutch when stopped and changing into or out of first (and reverse of course, although it was impossible do do this quietly!). It took a few days to get a feel for the gears, then the changes were smooth as silk.