Slick Shifting

[BLOWNMM]

Hi guys
I have become aware of a practice called ‘Slick Shifting’ which is meant to speed up a gear change. It was developed by American Hotrodder and Dragster guys in the late 40’s and 50’s. I am interested in hearing of any info first hand from anybody who has done this or any first hand info re the practice.
Bob

[bmcecosse]

Sounds like a gearbox breaker to me. Are you really in such a hurry that 0.1 seconds saved on gear shifting is important to you?

[BLOWNMM]

When gearchanging in a side valve box with antiquated cone synchros at 6000+ RPM double declutching is required. Even with a flywheel lightened mainly on the outer periphery by 2.6 Kilo's. this is painfully slow taking up to 4 - 5 seconds for the engine revs to slow down to enable selection of a higher gear. 0.1 seconds would be better than nothing however for hillclimbing 3 upchanges for a lost time of 12 - 15 seconds is not acceptable - done before even starting. Maybe someone with knowledge of the practice can reply with a more helpful suggestion.
Bob

[simmitc]

6,000+ RPM I'm interested to know what else has been done to the engine?

[bmcecosse]

Can only involve dragging the lever through - maybe even without dipping the clutch... Gearbox breaker for sure.

[amgrave]

The only slick shifting I have heard of is down shifting by raising the engine revs to match the gearbox revs, with practice you can do it with out using the clutch

[BLOWNMM]

Hi Guys
I have done a lot of research into the subject however was looking for maybe some input from MMOC forum members who had first hand knowledge. Have attached 2 links. The first a general outline and the second a specific reference where the poster was slick shifting a Mopar A568 box in a car with a motor with excess of 300 HP and 300 Lbs. ft. torque. These shifts were reportredly done in extremely fast times - see second link page 4 post # 65. It would appear that gearshift times can be obtained much faster than 0.1 seconds. However it would be more reassuring to hear from MMOC members if they have had hands on experience rather than guesswork.
Bob
http://www.atraonline.com/gears/2006/20 ... _05_60.pdf
http://www.turbo-mopar.com/forums/showt ... -Crash-Box

[BLOWNMM]

Hi Guys
My first car was a 1926 Dodge inherited from my grandfather. It had a non synchro gearbox - I also spent a couple of years in the army reserve driving WW2 Studebaker and GMC 6 X 6 trucks with 5 speed non synchro boxes. In a short while after becoming familiar - the clutch was not used - the difference between missing a gear when using the clutch and not using it was
next to nothing.
Bob

[BLOWNMM]

Hi Simittic
Dont know your first name hence the previous reference. My previous car was a 1948 Series E. I became aware of Morris 8 engined cars racing in the GEAR (Golden Era Auto Racers) and other classic car events. I learnt as much as I could from owners and decided to purchase a MM 1952 with basically the same motor. Armed with the knowledge gained from these guys I modified my MM motor. When the dissy curve was mapped and the carb needle chosen on a chassis dyno it produced 38.2 RWKw at 6000 Rpm. This equates to almost 63 flyeheel HP. Needless to say a lot of mods were made to enable this. Overboring by 3.0 mm., forged con rods, forged pistons, enlarged ports and valves, modified cam specs, the list goes on and on. Finally a roots blower pumping 15.2 PSI (a bit over 1.0 bar). Crank is stock standard. There have been several posts re this motor in the recent past. I have had the motor reving to well over 7000 RPM. This was only done to see that it could match that of the Morris 8 engined cars in the GEAR events. However because of the tremendous torque the blower produces at low RPM and the fact that the g'box synchros are almosy useless over about 4000 RPM I tend not to rev it too high.
Bob

[Chipper]

Any pics of this impressive sounding engine?

[les]

Is this a way of changing gear or does it entail a modification to the gearbox?

[simmitc]

Hi Rob, the list of mods certainly explains a bit more The original post didn't mention that it was a hot engine trying for a hill climb, hence Toy's earlier reply that why would you need to save the time. In a Minor, the Police teach good road driving with a definite pause in neutral and gentle selection - gives a really smooth ride; and probably what most people would like. However, there's nothing wrong with trying something different. although I'd be surprised if a standard MM box (and axle?) could take the sort of punishment being suggested; but it certainly sounds interesting. I too would like to se some pictures of the engine and car. It gives me an idea for the Inter Branch Challenge at next year's National Rally

Simon

[BLOWNMM]

Hi Guys
Les - requires modifying the gears as per the two links in the post above of July 20 at 10:26 PM. I have obtained a set of box internals from an old neglected one however there was enough to modify for a trial. It involves removing alternate dog teeth from the gears and alternate teeth from the sliders. Can only be done where the teeth are an even number.
Simon - the side valve gearbox is bullet proof and gear wise much stronger than smooth case and probably rib case. Also has a cast iron box. The fact that the number of dog teeth is halved means the power transmission capacity is halved. However I don't think my relatively low power will be sufficient to strip 12 dog teeth (or at least that's what I am hoping). The rear axle is a Minor 1000 with a 4.22 centre. The half shafts are EN 17 with a UTS of 1130 mP as compared to standard shafts made from EN 8 with a UTS of 700 mP. I do not expect problems from this department.
Chipper and Simon - pics of my car may be seen in the Series MM Register in a thread by Johhno titled 'oil filter' on Tue 5 July at 5:32 PM.
In the second link above the guy who modified the Mopar A568 box removed 18 dog teeth off leaving 18 to do the shifting. This means his box had 20 degrees for the engagement to occur. The MM synchros have 24 teeth leaving 12 to do the engaging. This means my modified box has 30 degrees for the engagement to occur - half as long again as the Mopar box. This makes me confident that the MM box will work probably better than the Mopar box. Have attached a pic of the modded gears. I first heard about it when reference was nade to removing male dog teeth to speed up gearchanging. I spent almost three days googling everything I could think of before the term 'Slick Shifting' appeared. Once this was googled numerous sites were found.
Bob

[les]

Thanks for the reply Bob.

[simmitc]

Ditto, and good luck, sounds very interesting.

[RobThomas]

MM box and back axle share design and components with Wolseley 4/44, 15/50 and MG YB and Z-types so is over engineered for the 27hp Minor. The 6-spline half shafts, for example, cope with 60 bhp in the Nuffield axle'd Z-types. T-type gearboxes look similar and I'd expect they us some of the same components.

MM with a TC engine and box would be nice.




I'd be happy if anyone could refute this info with any facts since it might be helpful in expanding the knowledge of the group.

[amgrave]

Never too old to learn are we. I have never heard of this but it's very interesting.

[BLOWNMM]

Hi Guys
The operation is basically converting a conventional box to essentially a dog box. The torque transmitted by the dog gears has to be momentarily interupted so as to allow the dogs to slide out. The guy with the Mopar box does it by jabing the clutch. The V/8 Supercars here in Oz have sequential boxes ie. all upshifts are by yanking the gearstick backwards. The gear lever is pivoted and when pulling back on the lever the pivot operates and momentarily operates a micro switch which kills the ignition via the ECU to unload the dog gears. This is done on the Holinger boxes formally used and the Albins now used. When watching the V/8 races there is no perceptable miss in the engine as these shifts are made in the 15 to 20 milliseecond range. However this cannot be done with the Morris box because one of the upshifts (2nd to 3rd) is by pushing the lever foreward. This is a no no because of the need to rev the motor for double declutching a downchange from 4th to 3rd and 2nd to 1st. for a trial I am thinking of a hand held microswitch to operate a relay to momentarily kill the ignition to enable the unloading of the dogs for a change to occur until I can come up with a better idea. Would be interested in hearing from anyone with any other ideas.
Bob

[amgrave]

How about mounting the kill switch at the top of the gear stick under the knob

[BLOWNMM]

Amgrave - good thinking. I have so much on my mind now the obvious was not thought of.
Bob