Dog engagement gear boxes

[AirCooln]

I've been in talks about my power plant for next year, and the subject of dog engagement gear boxes has arisen. I've never used one, and have not quite having mastered rev matching yet on a syncho box. Should I even consider one of these? Would it help the learning curve? Would the average person destroy the thing in a few laps because the skill isn’t completely there yet.

Thoughts and insight would be appreciated.

Admittedly this and straight cut gears certainly has a degree of coolness!

[slucas]

Have you thought about a straight cut close ratio 4 syncro box?
Maybe not as cool as a JK dog box but way less expencive.
How much HP/torque are you making?

I didn't have any trouble at all adapting to a dog box and in the case of a Mini they are much sturdier than the stock item.
Dog boxes seem to like being shifted quickly and with authority, just the sort of thing you want in a race car.Unlike most dog box racers ,I allways used the clutch;it's a Mini ... say no more.
There may be a number of used boxes around (I have 2) but be aware that they may have racing ratios that would kill you at a standing start (1.7 first gear , almost like starting off in 3rd gear)

[John Powell]

I've driven two race cars with crash boxes, and they weren't hard to get used to - it just takes a bit of practice. They do give faster, cleaner shifts, both up and down, and usually come with the ability to install different ratios for each gear, both of which may save you a few tenths of a second per lap, depending on the track. The downside is that these tenths usually come at a much higher price than a production-based gearbox. So, if you have the budget, go for it, and if not, suffer with us other poor sods. ;)

[Marsh]

I've never driven an H-pattern, but I've driven bike-engine powered cars and I thought it was quite easy to transition (actually 2nd autocross I ever drove was in an SAE car and I was clutchless shifting by the end of my first run).

[malcolm]

yeah, I've only driven sequentials... but remember, if you aren't certain about your rev-matching, you can still use the clutch on downshifts. It's only the upshifts where the clutchless shifts make a difference.

[Steven Scala]

Hooey.

Even if you are sure about your rev matching, I'd recommend dipping a bit of clutch on downshifts.

Likewise, unless you feel you need to be hard on the car in order to get the most out of it, giving a touch of clutch on upshifts is a good help. You can then reallocate a bit of your dog-ring budget into your tire budget...

Outside of karting, most of my racing was with a Hewland box. Back in the old Bridgestone Academy series, I consistently qualified on front row 'despite' giving cursory clutchpedal taps on up- and downshifts, against guys who were shifting clutchless. With the Hewland Mk9, at least, any differences between the two techniques could be measured in hundredths of a second - margins that are easily swallowed up by normal detail mistakes commonly made while driving over 9/10ths (especially on DOT radials with light downforce), or passing lapped traffic.

[AirCooln]

Thanks for the excellent feed back. Sounds much easier to live with with then I had anticipated. I thought you had the revs pretty much exact, or risk horrible noises and severely worn internal parts.

I went and secured a good used one this morning. Cant wait to try to try it out!

[Marsh]

Originally posted by AirCooln
I thought you had the revs pretty much exact, or risk horrible noises and severely worn internal parts.

For clutchless downshifting that's true, but just a little clutch pressure is enough to make it childs play, and anybody can updshift without the clutch (again I've never tried on an H patter, but I doubt it's that much harder?)

[malcolm]

in one formula car that I tested, left foot braking helped a lot, so I had to do clutchless downshifts, and they were fine... mind you, this was a sequential, so like Marsh, I am not 100% sure if the same would apply to H pattern...

edit:

I thought you had the revs pretty much exact, or risk horrible noises and severely worn internal parts.

that's the whole point of a dog-box. they allow the dogs to be a little out of sync, and still be able to engage. Sure, the farther they are out of sync, the higher the wear on the gearbox... but a little difference in speed isn't too bad.

[CobraStang]

The only clutchless shifting I've done is when I broke the clutch cable on my motorbike about 60 miles from home.
Starting at a green light without a clutch can be...interesting! :)

[Marsh]

Originally posted by CobraStang
The only clutchless shifting I've done is when I broke the clutch cable on my motorbike about 60 miles from home.
Starting at a green light without a clutch can be...interesting! :)

At least you can bump start a bike by yourself.