GSAP Question

[Deleted account 250319001]

At the end of the day if you don't use the clutch to allow some slip between engine and transmission, then the mismatch in their speeds when you change gear has to be absorbed somewhere else in the drivechain, putting more stress on it than when the clutch is used. Maybe those with all the sensitivity and mechanical sympathy of a rhino don't feel a thing, but it is still happening!

The software does exactly that

You'd better phone BMW head office and tell them of their flaw in their design

 

[fred_jb]

The software does exactly that

You'd better phone BMW head office and tell them of their flaw in their design

If the software was operating the clutch, as it does on a DCT system, then I would agree with you. However I believe this is not the case with the BMW quickshifter, or any other as far as I know, so this is primarily a mechanical issue. Therefore in this case the software can only mitigate the stresses of clutchless changes, it cannot eliminate them because the engine remains connected to the transmission during the gear change.

In contrast, when you use the clutch during a gear change you momentarily disconnect the engine from the transmission. This means that the drivechain only has to mechanically synchronise the speeds of the input and output shafts within the gearbox to suit the new ratio, which involves overcoming much less mechanical inertia than forcing the engine to adopt a suitable speed for the new ratio. Meanwhile the engine, because it is disconnected from the transmission, can easily have its revs dropped (when changing up) or raised (a blip when changing down) so that when the clutch plates re-engage the speeds of the engine and transmission are more or less equalised, and any remaining disparity is absorbed by some slippage in the clutch plates before they fully lock together.

Fred

 

[Deleted account 250319001]

The software does it all for you, in an instant. Cutting the power for a split 100th of a second on upshift, and blips it on a downshift.
The majority of those that disregard, or even slag off any new technology usually don't have it, and the saying "Its rubbish" makes them feel better.
they used to say you'd suffocate in a vehicle if you traveled more then 30 miles an hour. Glad they got that wrong LOL

 

[fred_jb]

The software does it all for you, in an instant. Cutting the power for a split 100th of a second on upshift, and blips it on a downshift.
The majority of those that disregard, or even slag off any new technology usually don't have it, and the saying "Its rubbish" makes them feel better.
they used to say you'd suffocate in a vehicle if you traveled more then 30 miles an hour. Glad they got that wrong LOL

Yes - and those software initiated actions mitigate the mechanical shock to the system which would otherwise be greater, but they don't and can't eliminate it. All that cutting the power though software does is make it a little easier for the transmission to forcibly reduce the engine speed to suit the new ratio as a higher gear is selected. Similarly the blip speeds up the engine just as one gear disengages and a lower one engages, so reduces the disparity between engine and transmission as the new lower gear takes over.

However you can't get away from the fact that you are forcing engine and transmission speeds to equalise to suit a new ratio while remaining connected. Without the benefit of the clutch, which is designed to make this process much easier and less mechanically stressful, then this does put more strain on the transmission. However, if you don't understand what a clutch does and why it is there, then there is no point in continuing the discussion.

This is just stating the facts - it is not knocking new technology. I have GSAP and I have previously owned a bike with DCT (dual clutch transmission) and to me GSAP is just a reasonably successful cludge, whereas DCT which has software control of the clutch is the real deal.

Fred

Edit: Definition of cludge: Slang. 1. A system, especially a computer system, that is constituted of poorly matched elements or of elements originally intended for other applications. 2. A clumsy or inelegant solution to a problem.

 

[MrMcNamara]

You’re the engineer, you tell us

I think we all know he is just full of S***e & no real world engineer

 

[ChazzyB]

Yeah, the quickshift down the box is so much a cludge that other premium manufacturers are falling over themselves to implement it on their bikes. The system is great. I love barreling towards a corner tip-in point, braking and down-shifting simultaneously, all without touching the clutch lever. Or trying to blip the throttle while also pulling hard on the front brake.


Oh, and yes, the GS does have a slipper clutch.

 

[Geekay]

The LC gs does have a synchromesh box though? There’s lots of talk here that it isn’t a synchro box. How does this change the discussion?

Scroll down to “transmission” and it states it’s a “6-speed helical synchromesh”

https://www.bmw-motorrad.co.uk/en/m...re/technicaldata.html#/section-technical-data

My 2016 gsa has GSAP and I have to say I love it. Up and down the box it work fantastically well. But I do sometimes feel a little unsympathetic using it to go down the box.



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[Prawnini]

The LC gs does have a synchromesh box though? There’s lots of talk here that it isn’t a synchro box. How does this change the discussion?

Scroll down to “transmission” and it states it’s a “6-speed helical synchromesh”

https://www.bmw-motorrad.co.uk/en/m...re/technicaldata.html#/section-technical-data

My 2016 gsa has GSAP and I have to say I love it. Up and down the box it work fantastically well. But I do sometimes feel a little unsympathetic using it to go down the box.



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For all the comments on this post I feel it is a great piece of kit and makes my ride enjoyable, what more do you all want??? It’s a feckin Motorcycle ffs!


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[fred_jb]

Yeah, the quickshift down the box is so much a cludge that other premium manufacturers are falling over themselves to implement it on their bikes. The system is great. I love barreling towards a corner tip-in point, braking and down-shifting simultaneously, all without touching the clutch lever. Or trying to blip the throttle while also pulling hard on the front brake.


Oh, and yes, the GS does have a slipper clutch.

I would agree that GSAP clutchless downshifts are less problematic than upshifts, and work quite well, maybe because it is quicker to increase engine speed with a blip while in the process of a downshift, than it is to slow the engine down for an upshift, so there is probably more of a speed mismatch when a clutchless upshift is made.

Also, as you say, for downshifts you do have the safety net of the slipper clutch on recent models which will prevent any tendency to lock the wheel if the engine speed is not quite synchronised when the lower gear engages.

I find it is the upshifts which make me wince a little because you can definitely feel the shock through the transmission. It is worse in the lower gears when you can easily feel it, but even in the higher gears you can feel or at least hear a muted thump as the gear goes in, which I don't particularly like.

It is still effectively taking a system which was originally designed to use a clutch and bolting hardware and software onto it to make clutchless changes less mechanically traumatic than they would otherwise be. Similar systems have been around for quite a long time now so I don't think it's a case of other people copying BMW.

Interesting comment on this here (taken from the Wikipedia page on quickshifters: https://www.cycleworld.com/2015/07/...shifters-have-negative-effect-on-gearbox-life

Fred

 

[ChazzyB]

The LC gs does have a synchromesh box though? There’s lots of talk here that it isn’t a synchro box. How does this change the discussion?

Scroll down to “transmission” and it states it’s a “6-speed helical synchromesh”

Well I never! Is that why I don't have to double-declutch on gear changes! Oh hang on, I've never had to do that on any bike...

 

[ChazzyB]

For all the comments on this post I feel it is a great piece of kit and makes my ride enjoyable, what more do you all want??? It’s a feckin Motorcycle ffs!

Shaun, I'm with you chum. I love it. And I think I'm mechanically more sympathetic than many I meet.

 

[Prawnini]

Shaun, I'm with you chum. I love it. And I think I'm mechanically more sympathetic than many I meet.

Cheers Charles, if I wish to use the clutch I can but why when it is a near seamless without it. If I ride it properly and change gear at the right time it works very well.


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[Geekay]

Well I never! Is that why I don't have to double-declutch on gear changes! Oh hang on, I've never had to do that on any bike...

I don’t get it?

I’ve read this whole thread and most of the way it was stated that it was not a synchromesh gearbox (comment 33 as an example). I was just saying that it is a synchromesh gearbox.

As I also said - I think it’s great and I use it a lot both up and down the box. And this is on my supposedly ‘poor’ 2016 model


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[Andrew997]

I don’t get it?

I’ve read this whole thread and most of the way it was stated that it was not a synchromesh gearbox (comment 33 as an example). I was just saying that it is a synchromesh gearbox.

As I also said - I think it’s great and I use it a lot both up and down the box. And this is on my supposedly ‘poor’ 2016 model


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I stand by comment 33 , regardless of what it says on the bmw website. For GSAP to work it must be a dog driven gearbox. Dog gearboxes don't have syncromesh.

 

[ChazzyB]

I don’t get it?

I’ve read this whole thread and most of the way it was stated that it was not a synchromesh gearbox (comment 33 as an example). I was just saying that it is a synchromesh gearbox.

As I also said - I think it’s great and I use it a lot both up and down the box. And this is on my supposedly ‘poor’ 2016 model


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I think I'm confused as to it being a synchromesh gearbox, as to my (limited) knowledge, motorcycle gearboxes are usually constant-mesh gearboxes. All the gears mesh and turn all of the time, but only one set transmit drive. Synchromesh gearboxes were developed to allow gear changes in cars without having to double-declutch or just crash through the gears. Bikes have never needed to do that. The handbook doesn't call it a synchromesh gearbox. I would place money on that being marketing bullshit.

 

[fred_jb]

I think I'm confused as to it being a synchromesh gearbox, as to my (limited) knowledge, motorcycle gearboxes are usually constant-mesh gearboxes. All the gears mesh and turn all of the time, but only one set transmit drive. Synchromesh gearboxes were developed to allow gear changes in cars without having to double-declutch or just crash through the gears. Bikes have never needed to do that. The handbook doesn't call it a synchromesh gearbox. I would place money on that being marketing bullshit.

Yes - I agree. Some of the stuff on BMW's website mentions synchromesh, but the term is notably absent from the more detailed descriptions. I would have thought that clutchless changes would be potentially quite destructive to a synchromesh gearbox.

 

[Engineer]

What a load of old tosh. MY GSAP is seamless and instant. No human hand and foot could make it more mechanically sympathetic........
Utter Tosh !

Not tosh at all, I can change gear far more smoothly than the GSAP especially downshifts.