The idiots guide to a dogbox

[wrightman90]

What is a dogbox? They sound amazing!

http://www.youtube.com/watch?v=dmJH84FnQa8&fea...

[Evil Edna]

I am more than prepared to be corrected but...........

I think you are getting confused between straight-cut gear boxes, where the meshed gear teeth are (yep, you guessed it) straight cut, not helical.

A dogbox refers to a 1st gear which is engaged when the gear lever is left and down. This leaves 2nd and 3rd in the same plane, opposite each other, as opposed to 1st and 2nd being opposite each other.

As demonstrated in the video clip, straight cut boxes are very noisy.

I think this is correct but, I am not 100% sure.

[Utterly Clueless]

I dont care what box it is, what it does or how it sounds.

that guy is NUTS a good driver but mind numbingly mental all the same.

Kudos to him i say.

[Ferg]

Evil Edna said:

A dogbox refers to a 1st gear which is engaged when the gear lever is left and down.

No, that's a 'dogleg'.

A dogbox describes how the gears engage, with 'dogs' rather than a synchro hub.

Edited by Ferg on Wednesday 29th April 19:59

[Evil Edna]

Ferg said:

Evil Edna said:

A dogbox refers to a 1st gear which is engaged when the gear lever is left and down.

No, that's a 'dogleg'.

Ahhhh......, I see.

So what are "dogboxes" then?

All conventional manual boxes (and DCT autos) have "dogteeth" gears that are engaged by a collar, which is moved by a selector fork, which is moved by the gear lever..........etc

The question still remains....what is the definition of a "dogbox"?

[crugbun]

I thought it was to do with the large 'dog' teeth on engagement gears instead of syncro baulk rings which wear out.. The gears are all straight cut for sure, but this alone does not a dog box make.
The whine is from the final drive, not the gearbox.

Edited by crugbun on Wednesday 29th April 20:08

[northandy]

Ruddy hell, how quick was that car compared to the others !!!

[LeeThePeople]

Ferg said:

Evil Edna said:

A dogbox refers to a 1st gear which is engaged when the gear lever is left and down.

No, that's a 'dogleg'.

A dogbox describes how the gears engage, with 'dogs' rather than a synchro hub.

Edited by Ferg on Wednesday 29th April 19:59

Thats how I understand it too, I bought my Evo with a dog box already installed and its by far quicker than similar powered Evo's.

[fastfreddy]

This will help you understand more what a dogbox is capable of:

http://www.youtube.com/watch?v=asFwDpLe1xo&fea...

[PJR]

crugbun said:

The whine is from the final drive, not the gearbox.

Generally, whining transmission noise comes from whatever parts have straight cut gears. Be it the final drive or the gearbox itself.
This can be demonstrated quite easily with most manual road cars. Reverse gear is nearly always straight cut, and you'll notice the noise then. But as you tend to go backwards slowly, the noise isn't quite a whine, but more of a mechanical groan, of sorts. Which turns into a whine as the speed picks up.

Back to the dog engagement shenanigans.. This in itself doesn't really account for any particular noise above a straight cut box (besides the odd crunch). Its just a crude, but robust way that the gear engagement is done. But the gears will wear faster.

P,

[Holst]

northandy said:

Ruddy hell, how quick was that car compared to the others !!!

I think he must have qualified well down the grid.
The cars he was supposed to be racing had gained such lead on him that you never see them in the vid, you just see him blasting past the slower classes, many of them move over to let him pass. Fantastic to watch though the way he overtakes so many people on the first lap.

[beejay]

What I think I know, FWIW

Dogbox, regular manual box with dog engagement. They have no synchronisers, just a dog clutch to engage the gears. Hence you have to rev match yourself when changing gear. On the plus side they're much easier to change without using the clutch as they will tolerate a relative high differential speed between gears when bashing them in. Also simpler than synchros and less delicate. Usually found in trucks, bikes and race apps.

Dogleg refers to the gear selector pattern. wiki article shows the layout. Puts the most used gears (ie 2nd and up) together over two gates hence a little quicker to scoot the shift lever about.

Straight cut refers to the gears themselves being cut, well, straight ie parallel to the axis of the shaft. Road gearboxes uses helical cut gears as they're much quieter, however they produce thrust loads along the shafts which can chew up shaft bearings quickly in race applications. SC gears are whats making all the noise in the vid

Seriously doubt the diff is making the whine. Its a RWD BMW hence "conventional" rear diff, it'll be a hypoid bevel of some type and hopefully quieter than that! Frequency would also suggest it's coming from something more high speed too, like a SC gearbox.

[Sam_68]

beejay said:

Dogbox, regular manual box with dog engagement. They have no synchronisers, just a dog clutch to engage the gears. Hence you have to rev match yourself when changing gear. On the plus side they're much easier to change without using the clutch as they will tolerate a relative high differential speed between gears when bashing them in. Also simpler than synchros and less delicate. Usually found in trucks, bikes and race apps.

Dogleg refers to the gear selector pattern. wiki article shows the layout. Puts the most used gears (ie 2nd and up) together over two gates hence a little quicker to scoot the shift lever about.

Straight cut refers to the gears themselves being cut, well, straight ie parallel to the axis of the shaft. Road gearboxes uses helical cut gears as they're much quieter, however they produce thrust loads along the shafts which can chew up shaft bearings quickly in race applications. SC gears are whats making all the noise in the vid

All Korrect!

I'd add that dog engagement boxes offer a much faster gearchange. Baulk ring synchromesh won't allow the next gear to engage until the speeds have synchronised.

Standard technique for upchanges on a dog box is to preload the gearlever with light finger pressure, then lift the throttle slightly to unload the gears, whereupon the dogs will disengage and the next gear will select itself pretty much instantaneously, and you can be back on the power as fast as you can move your foot. They're the quickest way to change gear that there is, without resorting to tricksy electronic paddleshift stuff.

...and you don't have to rev match, it's just kinder to the dogs if you do.

Also, the main reason for using straight-cut gearboxes for racing is not due to the thrust loads in helical gears, but simply that they absorb a lot less power.

I've got a straight-cut, dog-leg and dog-engagement box in one of my cars; FWIIW, the noise isn't so appealing by the time you've done a 300-mile cross-country round trip sitting next to it. If a straight-cut box for regular road use appeals, spending a couple of days with a Black and Decker hammer drill strapped to one ear, at full revs, should give you some idea what you're letting yourself in for!

Edited by Sam_68 on Wednesday 29th April 22:55

[wrightman90]

Sam_68 said:

beejay said:

Dogbox, regular manual box with dog engagement. They have no synchronisers, just a dog clutch to engage the gears. Hence you have to rev match yourself when changing gear. On the plus side they're much easier to change without using the clutch as they will tolerate a relative high differential speed between gears when bashing them in. Also simpler than synchros and less delicate. Usually found in trucks, bikes and race apps.

Dogleg refers to the gear selector pattern. wiki article shows the layout. Puts the most used gears (ie 2nd and up) together over two gates hence a little quicker to scoot the shift lever about.

Straight cut refers to the gears themselves being cut, well, straight ie parallel to the axis of the shaft. Road gearboxes uses helical cut gears as they're much quieter, however they produce thrust loads along the shafts which can chew up shaft bearings quickly in race applications. SC gears are whats making all the noise in the vid

All Korrect!

I'd add that dog engagement boxes offer a much faster gearchange. Baulk ring synchromesh won't allow the next gear to engage until the speeds have synchronised.

Standard technique for upchanges on a dog box is to preload the gearlever with light finger pressure, then lift the throttle slightly to unload the gears, whereupon the dogs will disengage and the next gear will select itself pretty much instantaneously, and you can be back on the power as fast as you can move your foot. They're the quickest way to change gear that there is, without resorting to tricksy electronic paddleshift stuff.

...and you don't have to rev match, it's just kinder to the dogs if you do.

Also, the main reason for using straight-cut gearboxes for racing is not due to the thrust loads in helical gears, but simply that they absorb a lot less power.

I've got a straight-cut, dog-leg and dog-engagement box in one of my cars; FWIIW, the noise isn't so appealing by the time you've done a 300-mile cross-country round trip sitting next to it. If a straight-cut box for regular road use appeals, spending a couple of days the a Black and Decker hammer drill strapped to one ear, at full revs, should give you some idea what you're letting yourself in for!

Thanks very much for the responses, much appreciated. What car do you have a dog-engagement box fitted to, and how much are they to buy (sam_68)? Are further modifications required to your car for them to work?

[Sam_68]

wrightman90 said:

What car do you have a dog-engagement box fitted to, and how much are they to buy (sam_68)? Are further modifications required to your car for them to work?

Mine's a Hewland LD200 5-speed and it's fitted to the Westfield on my profile.

Cost depends on the box (application, how many gears, H-gate or sequential etc.). Have a look at Hewland's web site or Quaife's web site to get some idea. I'm thinking about changing my dogleg LD200 for a sequential Hewland JFR, and it would cost me about £5,500+VAT, plus the custom components to make it fit my particular installation (mounting brackets and, on the FW400, a nose-piece casting to carry a bearing for a long input shaft, to reduce the length of the propshaft and so prevent 'whirling')

Assuming you can find one that's specifically designed to fit your car, there's no particular need to change other components, though in practice you'll often need new propshafts/driveshafts, mounting brackets, linkages etc. to complete the installation of a 'standard' dog box from a company like Quaife.

I really wouldn't recommend one for road use, though - the gearchange is very fast and satisfyingly positive on the track, but for road use, apart from being irritatingly noisy, they're pretty clonky in traffic and the dog rings are basically a service item, designed to be frequently replaced (every season's racing is not unusual).

Edited by Sam_68 on Wednesday 29th April 22:57

[windy1]

Crikey, the knowledge on this forum is laughable