30 replies to this topic

[GeoffR]

Is this getting close to a seamless transmission? I realise it is apure drag racing gearbox and only works on up shifts but seems to be pretty close to a seamless shift. 

 

 

[kikiturbo2]

apart from the lever mech, it is just like any other dogbox, or sequential dogbox, used in other forms of racing..

[PeterScandlyn]

For a non-tech person (myself) that was a brilliant piece. Thanks GeoffR   

[Lee Nicolle]

apart from the lever mech, it is just like any other dogbox, or sequential dogbox, used in other forms of racing..

That style of shifter has been around for decades, drag racers were using them on Muncies in the 60s. The tear the crap out of regular synchros as they change really fast. Here in Oz we had the Impala straightline shifter.  drag racers used them on Ausisie 4 speeds in the 70s.

These days Dragracers are all girlies with their automatics!!

Though WHY on earth do they persist with bloody Powerglides, 2 speed auto is plain stupid. 1950s tranny behind modern engiones!! Drrr.

Turbo 400s and Torque flites make some sense. Though modern 4 speed autos should be better, as well as stronger. 

Though the Dodge 8 speed is too many

[mariner]

A nice piece of brutal old fashioned engineering - and I'm not being sarcastic saying that.

 

Way back some US Dirt Modified car guys used a 2 or 3 speed Powerglide without any torque converter . The front pump which drives the clutch lock up had a by pass hose plumbed in leading to a lever controlled valve in the cockpit. At the start you closed this by pass valve and the clutches locked up. Then you used the manual shift override to switch gears if needed. On dirt tracks you usually stayed in top and I guess some of the brutality of a clutch shift without any torque converter cushioning was reduced by the low adhesion on dirt.

 

Anyway you could throw the thing away if it got worn as US junkyards were full of old Powerglides at low cost.

 

More here https://www.jalopyjo...erglide.367610/

[Greg Locock]

I had a box made for the EB 4 speed gearbox that allowed me to switch to any gear and lock the lockup clutch. So i could drive it like a manual. Obviously the LUC wasn't designed to act like a real clutch, and would have burnt out if used for real starts. But for testing while moving it all worked very well.

[gruntguru]

I did the same on a VN Commodore. Just a switch wired to the OBD connector allowed you to lock the TC. Great for towing - could haul a heavy trailer uphill in any gear you chose (except 1st).

[Greg Locock]

The production EB gearbox was calibrated so if you put it in '3' then it held 3rd gear with the LUC engaged. This was worth about 5 l/100 km when towing a big horse trailer at high speeds.

[gruntguru]

I used to own an EF - probably the same story as the EB. I would often pull the stick back to third, uphill on the highway. Even without a trailer I could see a couple of litres/100km improvement vs leaving it in "D" and letting it unlock the TC.

 

Interesting how most autos are not necessarily calibrated for best economy under all conditions. I was towing a big trailer on the highway with a current Isuzu diesel ute recently. Cruise control on - 100 km/hr. Left in "D" it would unlock the TC when the grade dragged the speed down to about 95 and the trip computer showed a big jump in fuel usage. Putting the shifter in the "manual" side of the gate, it would stay in top gear, hold the speed better and use 1 or 2 l/100km less.

Edited by gruntguru, 24 September 2018 - 22:02.

[GeoffR]

So having started this thread in regard to quick shift (seamless) gear boxes, and being an old rally freak, what gear boxes are a number of cars in this clip using, where there is a minimal audible between gears??

[Kelpiecross]

I think there is quite a difference between the gear changes as in the first gearbox video and the "seamless" changes as in F1. The "seamless" changes in F1 are so quick that (allegedly) two gears are actually engaged at once so there is no interruption of power flow at all. Presumably the two-gears-at-once situation is allowed by slight the flexing of the gear teeth - normally two gears engaged at once would result in a mighty crunch and bits flying in all directions.
I have read that F1 would use epicyclic gear layouts and clutch packs etc. if it were allowed by the regulations.

[kikiturbo2]

So having started this thread in regard to quick shift (seamless) gear boxes, and being an old rally freak, what gear boxes are a number of cars in this clip using, where there is a minimal audible between gears??

 

 

Most of these rally cars, as well as all R2, R4 and R5 cars use sequential dog boxes with some sort of load cell in the lever that is used to detect a shift and execute a short ignition cut. WRC cars use the same but with a hydrauilc/pneumatic/electric actuator. The same is true of all the GT3 cars, porsche cup cars, etc. The base is the same, mechanical sequential box with or without maunal actuation. The main reason for automation, as in pneumatic/hydraulic actuation is actually in the longevity of the box, not the speed of the shift. With automatic actuation you get the right shift every time, as dogboxes actually like fast shifts, and not being agressive enough will damage them + with automation you can program in a perfect throttle blip.

As for F1, I presume those gearboxes are much more advanced but never opened one of those..

[kikiturbo2]

I think there is quite a difference between the gear changes as in the first gearbox video and the "seamless" changes as in F1. The "seamless" changes in F1 are so quick that (allegedly) two gears are actually engaged at once so there is no interruption of power flow at all. Presumably the two-gears-at-once situation is allowed by slight the flexing of the gear teeth - normally two gears engaged at once would result in a mighty crunch and bits flying in all directions.
I have read that F1 would use epicyclic gear layouts and clutch packs etc. if it were allowed by the regulations.

 

With a normal dogbox you have a lot of play in the dogs... gears always mesh. With a lot of play in the dogs you can allow for two gears to be engaged for a brief ammount of time so that when the next dog set makes contact the first one will loosen up and can be disengaged quickly.... This is only my presumption of how it works though.. But my initial info of there being lots of play in the dogs is a fact..

[Kelpiecross]

I think that with the gearbox in the video there is clearly a "neutral" when the sliding dogs are not engaged to either gear set. From what I can research on the internet the F1 "seamless" gearboxes are essentially the same - except that there are two separate computer-controlled hydraulic-actuated shift systems that allow only a couple of milliseconds between one gear being disengaged and another being engaged - a couple of milliseconds, being for all practical purposes, instantaneous or "seamless". Apparently different F1 teams use slightly different and secret methods. I seem to recall that there was much discussion and argument on this forum about this subject a few years ago. I think "Autogyro(?)" got banned from the forum because of his continued insistence that the shifts were not (and could not be) "seamless" but that there must be some very slight time gap of no power flow during the change. Looks like he might have been right after all.

[kikiturbo2]

it really depends on what you call a shift.. in a dual clutch trans you can have seamless shifts and it is implemented like that in some cars... As for dogboxes.. sure, you have to have a point where the dogs do not touch anything, otherwise there would be no neutral.. However, if you have separate actuators for each shift fork, you can engage the next gear, wait a bit for the dog to make contact, and then pull out of the previous gear... if you have fast controll and actuators that is... that would be seamless in a sense that it would be uninterupted... True seamless doesnt exist in a mechanism with individual gears as the meaning of seamless would be that you wouldnt notice the change...

 

As I said in that "fight" we had about seamless..  just launch a porsche 991 turbo S from standstill and you will see a 1-2 shift where it will engage second and accelerate trough the shift.. it is a weird and wonderfull feeling, even though I dont like dual clutch boxes..

[Lee Nicolle]

A nice piece of brutal old fashioned engineering - and I'm not being sarcastic saying that.

 

Way back some US Dirt Modified car guys used a 2 or 3 speed Powerglide without any torque converter . The front pump which drives the clutch lock up had a by pass hose plumbed in leading to a lever controlled valve in the cockpit. At the start you closed this by pass valve and the clutches locked up. Then you used the manual shift override to switch gears if needed. On dirt tracks you usually stayed in top and I guess some of the brutality of a clutch shift without any torque converter cushioning was reduced by the low adhesion on dirt.

 

Anyway you could throw the thing away if it got worn as US junkyards were full of old Powerglides at low cost.

 

More here https://www.jalopyjo...erglide.367610/

A power slide is a 2 speed, a tough old thing but has TWO gears. Fast and faster! And dropped from use in 1968!! So at best 50y/o

Using autos on dirt has not been uncommon. more so IF the class does not allow a quick change diff. Plus some people do not seem to have kept manual boxes together.

Yet in the not so distant past I know of a car that was on the pace and had a 6cyl Holden gearbox and an Austin A90 diff. With a happy little 450hp Chev engine. This mid / late 90s!

One other not quite so on the pace but still competitive used a  converterless powerglide and a Morris LC3 diff, and that this century.

[Lee Nicolle]

I used to own an EF - probably the same story as the EB. I would often pull the stick back to third, uphill on the highway. Even without a trailer I could see a couple of litres/100km improvement vs leaving it in "D" and letting it unlock the TC.

 

Interesting how most autos are not necessarily calibrated for best economy under all conditions. I was towing a big trailer on the highway with a current Isuzu diesel ute recently. Cruise control on - 100 km/hr. Left in "D" it would unlock the TC when the grade dragged the speed down to about 95 and the trip computer showed a big jump in fuel usage. Putting the shifter in the "manual" side of the gate, it would stay in top gear, hold the speed better and use 1 or 2 l/100km less.

Ford 4 speed autos are ok for towing,, with the proper cooler. Really you should lock in third and performance mode for towing.  But if you are very aware you can use 4th [overdrive] for quite long distances. But as soon as the engine starts to lug put it back in third. And still use cruise

My Landcruiser,,, not so friendly. 110k, turn cruise on and it goes back to third and a thousand+ rpm more.  That is with the 5 speed auto which still has a full 500 rpm gap between 4th and 5th. Even driven solo it goes back to third when you simply kick it back to overtake. And at 3500 rpm does not really accelerate anyway.

But when towing in cruise you see 3500 far too often,

The previous 4500 4 speed  auto one was far better and torquier And used no more fuel.

Short stroke V8s are hardly good for towing in a 2.5 tonne 4wd

[Lee Nicolle]

There is numerous brands of racing dogboxes around from the US. Jerichos, G Force, and earlier  Sainz,  Doug Nash which became a Richmond made item. All have their good and bad points and all have been used with vertical gate shifters for drag racing.

Or H patterns for road and oval racing. The Richmond comes as a race box with dogs or a sychro box for street use.

Plus ofcourse Bert boxes, and others that are 2 speed with a reverse  for dirt. With couplers instead of a clutch

[Lee Nicolle]

Most of these rally cars, as well as all R2, R4 and R5 cars use sequential dog boxes with some sort of load cell in the lever that is used to detect a shift and execute a short ignition cut. WRC cars use the same but with a hydrauilc/pneumatic/electric actuator. The same is true of all the GT3 cars, porsche cup cars, etc. The base is the same, mechanical sequential box with or without maunal actuation. The main reason for automation, as in pneumatic/hydraulic actuation is actually in the longevity of the box, not the speed of the shift. With automatic actuation you get the right shift every time, as dogboxes actually like fast shifts, and not being agressive enough will damage them + with automation you can program in a perfect throttle blip.

As for F1, I presume those gearboxes are much more advanced but never opened one of those..

Which is similar to the gearboxes used in V8SC with the ignition cut.

You look with the in car footage of these cars and when they make a mistake you end up totally in the wrong gear as you have to row through the box for the right gear, whereas a H pattern  you simply go through the gate for the right gear.

That is the reason for those many seconds lost doing so. 

But dog boxes have been around for probably a 100 years... or more.Early cars and trucks had them. Just improved technology these days to make them both fairly light and fast to change.

Look at PPG here in Adelaide, they convert many production boxes to dog actuation which are used a LOT in rallying and overseas small cappacity racing as well

And they do a T5 version for full size Aussie cars as well

[blkirk]

I've seen drag racing dog boxes where the dogs have ramps on the back side.  The selector is split so that 1st stays engaged while you slide it into 2nd.  Once 2nd engages and overdrives 1st gear, the 1st gear dogs try to back drive.  Since the back sides of the dogs have ramps, the ramps just kick the 1st gear selector out of engagement.  It works great for drag racing, but would be totally useless in a road race.  The transmission would pop into neutral every time you lifted off the throttle.

[blkirk]

it really depends on what you call a shift.. in a dual clutch trans you can have seamless shifts and it is implemented like that in some cars... As for dogboxes.. sure, you have to have a point where the dogs do not touch anything, otherwise there would be no neutral.. However, if you have separate actuators for each shift fork, you can engage the next gear, wait a bit for the dog to make contact, and then pull out of the previous gear... if you have fast controll and actuators that is... that would be seamless in a sense that it would be uninterupted... True seamless doesnt exist in a mechanism with individual gears as the meaning of seamless would be that you wouldnt notice the change...

 

As I said in that "fight" we had about seamless..  just launch a porsche 991 turbo S from standstill and you will see a 1-2 shift where it will engage second and accelerate trough the shift.. it is a weird and wonderfull feeling, even though I dont like dual clutch boxes..

 

If I were building a dual clutch transmission, I would put hall sensors on each end of the gear shafts.  By watching the phase shift between them, I could work out how much torque each shaft was transmitting.  Feed that back into the clutch control algorithm and you can synchronize the slippage of the clutches over a short period of time to smoothly transfer the load from one shaft to the other.

[kikiturbo2]

actually they do work like that. Individual shaft speed and slippage is an input parameter. Dual clutch boxes will actually allow some slip, depending on driving mode, to increase comfort.

I have seen porsche pdk box actually engage both clutches at the same time to allow for a fully seamless shift and maximum acceleration. First time you feel it it is quite weird..

[blkirk]

actually they do work like that. Individual shaft speed and slippage is an input parameter. Dual clutch boxes will actually allow some slip, depending on driving mode, to increase comfort.

I have seen porsche pdk box actually engage both clutches at the same time to allow for a fully seamless shift and maximum acceleration. First time you feel it it is quite weird..

 

I never could understand why that one guy fought the idea so hard.  Either he was denser than lead or the most determined troll I've ever seen.  It could go either way.  Even in single clutch transmissions, there is always a moment of slip as you engage each gear.  The length of the slip controls the tradeoff between clutch life and gear life/passenger comfort.  Short slips are bad for the gears and passengers.  Long slips are bad for the clutch.  But I expect everyone here already knows all of this.

[gruntguru]

I never could understand why that one guy fought the idea so hard.  Either he was denser than lead or the most determined troll I've ever seen.

 

He was a transmission "expert". Even experts can sometimes fail to understand a basic concept.

[mariner]

auto shift certiianly does aid transmission longevity. Tony Southgate tells the story of how, soon after he joined Audi as the Le Mans design consultant, a young guy came to the Audi office with a simple gadget.

 

It was a pneumatic shifter he had designed for mototbikes and Tony plus Audi realised it was the answer to the Le Mans teams dreams as it reduced shifting wear.

 

That alone made it worthwhile as transmission failure was BIG Le Mans problem, Audi even re-designed the car to speed up mid race box changes 

[Kelpiecross]

This is how a seamless 'box works:


He doesn't mention that none of this would work without the use of a double re-entry over-and-under confabultor manifold incorporating a spondulo valve.

Edited by Kelpiecross, 06 October 2018 - 13:44.

[Kelpiecross]

Here is the original discussion on seamless gearboxes:
https://forums.autos...less-gearboxes/

A pain-in-the-arse old Gerrard (aka Autogyro) may be but he is more correct than incorrect. Seamless 'boxes shift in a couple of milliseconds but they are not truly "seamless". A typical road-going automatic (even going right back to Borg Warner DGs of the early fifties) are actually seamless as there is no interruption of power flow - two gears are engaged at once and the clutches/bands slip appropriately to adjust to the different gear speeds over the change.

A truly "seamless" 'box would actually be illegal in F1 as it would constitute a type of CVT. Which is why epicyclic arrangements are not allowed in F1.

[Kelpiecross]

I've seen drag racing dog boxes where the dogs have ramps on the back side.  The selector is split so that 1st stays engaged while you slide it into 2nd.  Once 2nd engages and overdrives 1st gear, the 1st gear dogs try to back drive.  Since the back sides of the dogs have ramps, the ramps just kick the 1st gear selector out of engagement.  It works great for drag racing, but would be totally useless in a road race.  The transmission would pop into neutral every time you lifted off the throttle.

I think the gearbox in the original video above may be of this type you describe. Note the ramps on the dogs and the split selector. A "normal" constant-mesh dogbox (as in a truck doesn't have the split sliding selector rings. I think a "seamless" 'box as in F1 may be of this basic layout but with the shifting (and timing) by hydraulics and computers etc.

Edited by Kelpiecross, 08 October 2018 - 09:40.

[kikiturbo2]

auto shift certiianly does aid transmission longevity. Tony Southgate tells the story of how, soon after he joined Audi as the Le Mans design consultant, a young guy came to the Audi office with a simple gadget.

 

It was a pneumatic shifter he had designed for mototbikes and Tony plus Audi realised it was the answer to the Le Mans teams dreams as it reduced shifting wear.

 

That alone made it worthwhile as transmission failure was BIG Le Mans problem, Audi even re-designed the car to speed up mid race box changes 

 

yeah, I was told once by guys in porshce motorsport that when carrera cup cars went from manual sequentials to pneumatically operated sequentials there was a marked drop in the ammount of gearbox maintenance and repair required. And the gearbox was basically the same...

[GeoffR]

Sorry for the bump for this thread, but listening to an in-car with Craig Breen on Rally Finland's Shakedown stage in a Hyundai i20 WRC, there appears to be no discernible pause with gear changes, almost super fast automatic transmission ..........

 

https://www.youtube....h?v=H_f6wWHrs4Y

[kikiturbo2]

WRC still uses a sequential dogbox but is is pneumatically operated (or hydraulically, or with some other powered actuator)... combine the ecu control of the actuation, with really precise ignition cut  and you get really fast shifts....