Gear changing on sequential BEC's?
Discussion
Hi,
I've read that upshifting on a sequential gearbox on my Westfield Megablade should be done as follows: Pre-load the gear lever, lift off the throttle briefly whilst changing up (without the clutch) and then straight back on the accelerator. Having tried this out earlier this evening on a blast around Sussex it certainly seemed far quicker than the usual clutch way when screaming up through the gearbox, and I've got it down to an almost seemless shift that takes fractions of a second, however I'm concerned that this is damaging the box - is this the case? What's the recommended way of shifting up through the box?
I haven't found a good way of downshifting, should this be done in the usual way (i.e. similar to a car gearbox, with the clutch?). The other thing that I hear is recommended is shifting as quickly as possible (both up and down) is the best way of minimising wear to the gearbox - is this right?
Cheers!
I've read that upshifting on a sequential gearbox on my Westfield Megablade should be done as follows: Pre-load the gear lever, lift off the throttle briefly whilst changing up (without the clutch) and then straight back on the accelerator. Having tried this out earlier this evening on a blast around Sussex it certainly seemed far quicker than the usual clutch way when screaming up through the gearbox, and I've got it down to an almost seemless shift that takes fractions of a second, however I'm concerned that this is damaging the box - is this the case? What's the recommended way of shifting up through the box?
I haven't found a good way of downshifting, should this be done in the usual way (i.e. similar to a car gearbox, with the clutch?). The other thing that I hear is recommended is shifting as quickly as possible (both up and down) is the best way of minimising wear to the gearbox - is this right?
Cheers!
Yep all good advice, clutchless upchanges are fine as long as you're getting them right which sounds like you are. Downchanges should always be with the clutch but as you've been told, do everything as quick as possible as there's no syncromesh like in a normal car so just bang it down as soon as you start dipping the clutch to minimise the time the dogs are in partial engagement.
I also find its better if you're changing down a few gears (and therefore braking for a couple of seconds or more) to do most of your braking first then bang down all the required gears in quick succession, rather than banging it down and getting lots of engine braking at higher revs.
I also find its better if you're changing down a few gears (and therefore braking for a couple of seconds or more) to do most of your braking first then bang down all the required gears in quick succession, rather than banging it down and getting lots of engine braking at higher revs.
Edited by LocoBlade on Wednesday 12th September 21:54
Cheers Chris (not Colin), more good advice! One more thing - I still can't get hold of Colin Denyer, but having booked the car into Westfield to get the RAC rollbar fitted next weekend (they'll fit it for £300 which I thought was quite reasonable considering the amount of cutting required), they offered to do a complete suspensio set up as they would a factory car for £180. This seems a bit steep, but I'm guessing once it's done, only needs looking at every year or so, what are your thoughts? Just unsure once it's set up, how often it needs checking, and therefore whether it's worth just paying them to do it.
Cheers!
Cheers!
I shift up in my fireblade car in a similar way. I don't bother pre-loading the gear though, I just back off a fraction and move the gear stick firmly. Works best when caning it, if I'm pootling I use the clutch. On the downshift I'm told it is possible to change without the clutch but I can't get it right so I just stick to using the clutch and a bit of heel and toe where needed. On track I do a lot of braking in a straight line in the high gear and then very quickly bang down the box just before the corner so I only need to balance the revs in the lowest gear. Gawd knows if it's the right way but it works for me. My (uprated) clutch has lasted nearly 5k so far with umpteen trackdays and some very dodgy trailer loading at times so it's not doing too bad.
Bike gearboxes are dog engagement, rather than the synchromesh found on road car boxes.
Hewland's website gives some good advice on how to treat them.
Edited to add:
Apart from the clutch (which, as Jubal's post suggests, can be a weak point on BEC's), your main problem is that incorrect use will knock the dogs off over time. Again, this situation is worsened with a BEC because the dogs were designed to be working against much lower loads in their original (bike) application.
Hewland's website gives some good advice on how to treat them.
Edited to add:
Apart from the clutch (which, as Jubal's post suggests, can be a weak point on BEC's), your main problem is that incorrect use will knock the dogs off over time. Again, this situation is worsened with a BEC because the dogs were designed to be working against much lower loads in their original (bike) application.
Edited by Sam_68 on Thursday 13th September 12:20
Hi James
I'd check/search on the Westie site to see people's thoughts on the standard factory setup because I seem to recall mixed comments on it, it may be more road biased for example which is not what you want if you're planning lots of trackdays. A better bet for track biased setup may be http://www.racecardoctor.co.uk/, Dave is on Pistonheads (here) and based down in Kent I think. He's set up quite a few track Westies including his own S2000 engine'd car which is very tasty.
Sorry you've not been able to get hold of Colin though, I did call him after posting the number and gave him a heads-up that you may be calling so I know the mobile still works. If you're still interested for future maintenance you can email me your details and I'll get him to call you back.
Chris
I'd check/search on the Westie site to see people's thoughts on the standard factory setup because I seem to recall mixed comments on it, it may be more road biased for example which is not what you want if you're planning lots of trackdays. A better bet for track biased setup may be http://www.racecardoctor.co.uk/, Dave is on Pistonheads (here) and based down in Kent I think. He's set up quite a few track Westies including his own S2000 engine'd car which is very tasty.
Sorry you've not been able to get hold of Colin though, I did call him after posting the number and gave him a heads-up that you may be calling so I know the mobile still works. If you're still interested for future maintenance you can email me your details and I'll get him to call you back.
Chris
Edited by LocoBlade on Thursday 13th September 20:00
andygtt said:
Think by load he means weight
Yep, but (in acceleration at least) you can only apply as much load/torque on the dogs as the engine can muster, just means it goes (relatively) slower with more weight.I did put the semi tongue in cheek bit though because I wouldnt disagree that overall, the gearbox gets a harder life in a car than a bike.
LocoBlade said:
Does the engine suddenly produce a lot more power (load) when its installed in a car then Sam?
No, of course not. But if the driver gets it even slightly wrong, then the dogs are being slammed into engagement against the resistance of 500kg sitting on 2x7" wide patches of sticky rubber and short final drive gearing, versus 275kg on a single, much smaller patch of rubber and much taller final drive gearing in their intended application.
As with the whole BEC vs. car engine argument, what ultimately matters is thrust at the tyre contact patches. BECS get their massive acceleration by using extremely short gearing to compensate for the engines' (relative) lack of torque. But, as we all know, for every action, there is an equal and opposite reaction. The corollary of using gearing to generate enough thrust at the tyres to accelerate 500kg very quickly is that it is reacted back through the transmission.
The power is the same, but the instantaneous loadings on the transmission, particularly if the driver gets it slightly wrong, are very much greater.
Again, I'd refer you to what Hewland (who know a thing or two about gearbox design
) have to say about the suitability of dog engagement gearboxes for road use.That's not to say they don't work. Just don't expect to get 200,000 mile intervals between rebuilds as you'd expect from a modern synchromesh gearbox.
Edited by Sam_68 on Friday 14th September 08:24
LocoBlade said:
andygtt said:
Think by load he means weight
Yep, but (in acceleration at least) you can only apply as much load/torque on the dogs as the engine can muster, just means it goes (relatively) slower with more weight.It's less-than-perfect gearchanging that destroys dog-engagement gearboxes, not the power/torque they are asked to transmit once the gear has been engaged.
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