Dog engagement gearbox / Layout

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german4inline
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Dog engagement gearbox / Layout

Post by german4inline » Sat May 09, 2015 2:38 pm

Guys,
is anyone experienced in gearbox technologies ? I want a dog gearbox for my Renault Alpine and a hungarian guy offers them for an really affordable charge. His appearently able to make the ratios to my desires and as well other nice Features as limited slip, helical gears a.s.o.
Probably some of you knows that dog engaments are sometimes critical in gear changing, to go higher is no problem with just flicking up the foot from the gas pedal without using the clutch.
Shifting downwards is much more tricky. When looking for information about that, I found a youtube of Pfitzner gearboxes where Pfitzner shows how to shift a dogbox in a Subaru (?) on public roads. It´s really impressive how smooth it works, amazing !
I guess it depends on how the dog geometry is designed, which angles on the gear engangements a.s.o. Is someone experienced in this technologies, how all that matters? Would talk with the hungarian that I want to ride the car sometimes in traffic, not only trackdays. Furthermore, I want to have helical cut gears to minimize the whine what makes you ringing the funny farm...

Brian P
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Re: Dog engagement gearbox / Layout

Post by Brian P » Sun May 10, 2015 10:51 pm

Every motorcycle has a dog-engagement gearbox.

There's a reason that they are sequential and without an (intentional) neutral anywhere except between 1st and 2nd (i.e. that you cannot select neutral at high road speed and then drop it into gear with a large difference in shaft speeds). False neutrals in those conditions tend to break stuff. Been there, done that.

autogear
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Re: Dog engagement gearbox / Layout

Post by autogear » Tue May 12, 2015 3:50 pm

Interesting!

Dog-rings aren't great for everyone; especially in street traffic. You can design a lower mass synchro to do a similar job in road racing as a dog ring; without the violence that can be imparted. For most club racers, this is way more than adequate, and much cheaper to maintain.

We are helical gearbox designers. You can see some work here http://www.powerblocktv.com/episode/MC2 ... VJXrrkhFxU

I suspect your hungarian friend is welding lugs onto existing helical gears. It can be done well, but it takes a lot of skill. If the welds are poor; they don't hold together well.

german4inline
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Re: Dog engagement gearbox / Layout

Post by german4inline » Tue May 19, 2015 5:22 pm

autogear wrote:Interesting!

Dog-rings aren't great for everyone; especially in street traffic. You can design a lower mass synchro to do a similar job in road racing as a dog ring; without the violence that can be imparted. For most club racers, this is way more than adequate, and much cheaper to maintain.

We are helical gearbox designers. You can see some work here http://www.powerblocktv.com/episode/MC2 ... VJXrrkhFxU

I suspect your hungarian friend is welding lugs onto existing helical gears. It can be done well, but it takes a lot of skill. If the welds are poor; they don't hold together well.
No, you are wrong. He doesn´t definitly weld on any dog rings or something. The gears are made out of billet as I´m really sure. It´s incredible what new parts the box features. It includes a LSD as well, looks really nice, maybe a bit too massive. What I don´t like is straight cut gears due to whining noises and the dogs are sharp edged what might causes poor gearchange quality once riding relativly slow in traffic ( thats not the usual condition, but might happen sometimes). My car is not just for circuit.
I know the solution to turn off the gears on sychromesh boxes and change the ratios by shrinking new gears on and do some TIG welding for safety. So you can keep the expensive synchro gears teeths in original condition. With the closer ratio, sychro works should work much quicker. I know some cars where it works without issues. Might be a solution for me if the dogbox wouldn´t work as I would like to do.

morerevsm3
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Re: Dog engagement gearbox / Layout

Post by morerevsm3 » Thu Jul 09, 2015 8:39 am

you have to be aggressive and firm with a dog box, try and be gentle like you do with a synchro box and you will damage it, and get false neutrals, here is a Samsonas dog box from Lithuania in my friends race car here in Australia-

https://www.youtube.com/watch?v=bthhTBNbgg4

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