straight cut or helical gears?

[Jono]

This is probably going to be a daft newbie question but..... .....can you have synchromesh with straight cut gears?
Jac Mac recommended I go for a Jerico or Tex Racing trans in my V8 Cortina fast road/track car (sorry non-'40 question again), but I think they are all straight cut and not sure if I can live without synchromesh as I'm too young and have always been pampered with synchroboxes in all my cars so far.

My other concern is noise, while it may not be an issue while on the track, I'm hoping to use it for weekend fun road driving as well, and if it sounds like this YouTube - Straight Cut Gears I think I may end up (a) deaf,and (b) single.
In case link doesn't work its a youtube vid, entitled "straight cut gears" posted by user TheGara.

What do you guys think, do many of you run straight cut on the street? How do you find them?

Thanks
Jono

 

[wanni]

Jono,
straight cutted does not mean noisly if some geometry strategies has been taken during the calculation. Long teeth with a thin base and grinded are not noisly at all.
The mission of straight cutted gears is to avoid axial forces which are generating losses and heat.
Why they are always togheter with dog ingagements?
Because the base of a tooth is wider in an helical gear then in a spur gear. The helix angle is higher by decreasing the width of the gear. This means that your gearbox shall be longer then it is if you want to transfer the same torque. That.s why the dog ingagement....because the stroke necessary to ingage the gear with dogs is about half of the stroke necessary to do it through a synchro. Generally we are talking about 5 mm for dogs and 9 mm trough a synchro. The 4 mm you gain in stroke could be used to increase the width of the gear.
Conclusions:
Angle with synchros = OK
Straight with dogs = OK
Angle with dogs = OK ++
Straight with synchros = KO - -

Ciao Wanni

 

[Sandy]

Jono -

I don't hear anything out of the ordinary in the video except the engine is too quiet, add a large solid roller cam to your build and loud exhaust and you should be fine, and I'm guessing you can drive around town wearing a helmet so you should be good. Someone should have stuff that driver into the wall, but he was quick and shifty to to speak OOps, not Nascar...

Seriously some people can't take the sound at all and it gets on their nerves very quickly. Others don't mind it at all. If it is a grocery getter and for picking up the kids at school, might not be a good idea. But if a racer, might just be fine.

I hate seeing people with a 10,000hp car fire pumping out of the pipes complain their car is loud or the A/C doesn't get cold and it's hard to hear the stereo. Screw that, race cars don't have a stereo Find really what you want for the car and that will likely dictate what you should do with the parts going into it.

One other option for gearboxes are the Richmond Gear T10's and the 5 and 6 speed synchromesh boxes. The Super T10's might only be Chevy style, but they do have 5/6 speeder for Fords. I have a 5 speed version of the Richmond box (not T10 style) and it seems like it is a very heavy box vs. T10's and a bit large. Another place to do some looking is for some of the small top loaders that seem to do ok, but are getting pricey as well. And don't throw out the idea of using a chevy gear box behind the ford, I think you can get several bellhousings and a pilot bearing that will do the job (I have a Tilton twin plate with that set up).

Last thing is somewhere I saw someone that was doing straight cut gear in either the Tremec TKO or WC T5's, but might not be worth it if expensive.

Great to have the Fox commenting and his expertise as well!

Sandy

 

[John S]

... and if it sounds like this YouTube - Straight Cut Gears ...

What a great circuit (I know, I live only 3 miles away from the Dutch TT-circuit)!
What you hear is not the straight cut gears, but the crown wheel (or whatever it's called).

John

 

[Jac Mac]

Jono,

If you MUST have a quiet trans then you could look into a 'New' toploader from David Kee.
Fairly old now and not the quickest shifter in the world but tough. Only two basic sets of ratios- wide with 2.78 low gear & close with 2.32 low gear. Input shaft is a bit marginal with lots of traction & torque; ie 15" wide slicks & 450 + ft lbs. Alloy case etc available for this, along with dog kits if you wish to say have dog engagement on 3/4 gear and synchro on 1/2 gears. Gears remain helical.That way you can keep your Ford ALLFORD with no substitute GM parts to weaken the drivetrain.

The BMW in the video sounded like it had an all indirect trans as the sound increased in direct relation to car speed a bit like a 'noisey' Quick Change, not engine RPM. A normal Hypoid CWP would be on its last legs if it made that much noise. I can honestly say I have never ever heard that much noise from a Jerico etc, in fact I would want to know why!
Have to say the guy driving was doing an excellent job.

You young overprotected fellas dont know what your missing, my first driving experience was on the farm tractors & trucks--All 'crash' box's, no synchro at all, ( and on occasions a similar amount of brakes ) you learn how to double clutch properly on downshifts real quick when its also your only means of slowing down!

Jac Mac

 

[Andy Besic]

I have to agree with Jack Mac. The noise in that video was the quick change rear end and not the trans.

 

[Sandy]

Hey Mr. Mac -

Thanks for the David Kee tip. I totally forgot about him. My 'Shelby Buddies' always talk about him but I always discredited them for no other reason to be different Jerico vs. TexTrans, etc. They look very nice and not crazy priced for a NEW gearbox, and hey, what's wrong with a Chevy gearbox on a Ford

Sandy

 

[Jac Mac]

Hey Mr. Mac -

and hey, what's wrong with a Chevy gearbox on a Ford

Sandy

Sandy----- Have you never watched that TV programme---- ''You are The Weakest Link''--

Jac Mac

 

[Jono]

Thanks guys, if most of the noise in that clip is from the rear end then maybe I shouldn't worry too much. Sandy, I take your point about people with noisy powerful cars complaining, (maybe this isn't the place to mention I was looking into ways to retain a heater while still shifting the engine backwards a fair distance.....), Like most I love the deep sound of a V8 and good exhaust, but whiney noises are a different thing.

The main issue for me is driveability rather than the noise, I'm wary of shelling out hard cash on a 'box only to find I'm not skilled enough to get the best out of the car cos I'm a molly-coddled product of the synhromesh generation. Can anyone explain a bit more how dog engagement boxes work (or post a link to a "gearboxes for dummies" website)? Be gentle, I'm aware I've got a lot to learn here....

As for Chevy vs. Ford box, I don't mind too much, as long as the engine is Ford based that will do for me. As it will be road driven at least some of the time, A richmond 5 or 6 speed does look attractive, especially as a road trip to Nurburgring is on the cards once my build is finished, 4th gear for a couple of hours on the Autobahn could be a bit testing.....

 

[Russ Noble]

Jono,

This is Hewlands recommendation for technique.

[SIZE=-1] "Manual.[/SIZE]
[SIZE=-1] Best method: With no assistance from the engine management, the driver must lift off the throttle sufficiently to allow the dog ring to be pulled out of engagement. He should then stay off the throttle long enough to allow the dog ring to engage with the next gear. In practice, the driver can move the gear lever faster than he can move his foot off and back on to the throttle. Therefore the effective method is to apply load to the gear lever with your hand and then lift the throttle foot off and back on to the pedal as fast as physically possible. In lifting your foot, the loaded gear lever will almost involuntarily flick to the next gear before the foot is re-applied to the throttle. [/SIZE]
[SIZE=-1] Another method is to load the gear lever with your hand, stay flat on the throttle and dab the clutch to release the dog ring. The overall effect on the gear shift is similar to the above method, but clutch wear may become a big issue.[/SIZE]
[SIZE=-1] The worst method (most destructive and definitely slowest) is to attempt to change gear in a `passenger car / synchromesh` way, i.e. lifting off the throttle, dipping the clutch, moving the gear lever, letting the clutch up and re-instating the throttle. The method causes unnecessary clutch wear, does absolutely nothing to help come out of gear and usually causes dog wear whilst engaging the next gear. This wear is due to several reasons. Firstly, it is impossible for a driver to co-ordinate the complicated sequence of all five physical movements accurately. Consequently the engagement dogs often find themselves engaging whilst the throttle is applied. The lever is usually pulled more slowly as it was not pre-loaded, lengthening the `danger zone`. [/SIZE]

[SIZE=-1]Successful down-shifting, has similar rules applied regarding speed of shift. Unloading the dogs is done in the opposite manner obviously. Whilst braking, the dogs must be unloaded by either touching the throttle pedal or- my preferred method- by dipping the clutch. However, one sharp dab of clutch or throttle is appropriate per shift. Continued pressure on either will cause dog damage for different reasons. `Blipping the throttle` just before engagement is advisable if the rev drops between gears are over 1300 rpm, as this will aid engagement and stabilise the car. [/SIZE]

[SIZE=-1]TOP TIP for ease of downshifting: Make the downshifts as late as possible in your braking zone (i.e. at lower road speed), because the rev drops between each gear are then lower. So many drivers make the mistake of downshifting as soon as they begin braking, causing gearbox wear, engine damage and `disruption` to the driving wheels. [/SIZE]

[SIZE=-1]This is a subject which can be much expanded on, but I feel that these are the basics, which I hope are of use."

Hope that helps. A bit different to the old truck type crash boxes that we all [/SIZE][SIZE=-1]learnt to drive with. [/SIZE][SIZE=-1](Well Jac Mac anyway! The rest of us are too young!!)

Cheers,
[/SIZE]

 

[Jac Mac]

Thanks guys, (maybe this isn't the place to mention I was looking into ways to retain a heater while still shifting the engine backwards a fair distance.....), As it will be road driven at least some of the time, A richmond 5 or 6 speed does look attractive, especially as a road trip to Nurburgring is on the cards once my build is finished, 4th gear for a couple of hours on the Autobahn could be a bit testing.....

Jono,

Pardon my warped sense of humour, but the heater issue wont be much of a problem with the motor set back around 12", dont even try to retain the original, it will turn into an engineering nightmare- have a look at some fwd control vans etc, they often have heaters that are remote from the screen etc and can be fitted in a more convenient area & ducted to the reqd areas.

Richmond-- only the 6 speed is OD in top, 5spd is 1 to 1 in 5th.

Jac Mac

 

[Dutton]

Jono,

Initially I refrained from commenting because your post asked for street impressions and, as I never had a dog box on the street, I just can't help you there. Like more than a few in the group, however, I did spend quite a few years (and too many $$) racing and I can tell you, without any doubt, that driving a car with a straight-cut-gear-dog-ring-box was one of the most enjoyable experiences I've ever had with a transmission.

Keeping in mind that my time with this kind of box was on-track, I never even considered the whine because, for the most part, it just wasn't all that noticable. These transmissions are a snap to learn; if you're competent using a synchro box, you won't have a hard time at all learning how to shift, up or down. In my case I found the learning curve for matching revs on a downshift the challenging part. No doubt you'll pick it up faster than I did...

The boxes are really simple to disassemble/reassemble when it comes time for new dog rings. A wise move would be to pick up a manual on the trans before you start a disassembly for the first time, pay attention to the order of assembly and orientation of the parts, and torque things correctly when you're done. It really is a walk in the park!

The only part of the maintenance some aren't fond of is having to remove and install the trans now and again. If you're good with that (or have a dependable crew), you're set.

Best,

T.

 

[Iain]

Jono,
Not sure if this of any interest to you but here goes. The racing "scene" here in Australia is dominated by what are locally described by V8 Super cars the entire field without exception use a 6 speed H pattern gearbox manufactured locally by an engineering compay in Melbourne called Holinger Engineering, ( I know its sacrildge (Spell check ) to mention the P word but he also manufactures all the gear sets for the 2007 Carrera Cup 997's, thats right the Porsche factory buy their racing gear sets from Australia). The Super cars are front engine cars with windsor V8s. I have the same box in a Cobra that I have been racing for 5 years. The gear sets are all dog tooth engagement but are helical cut not straight cut, apart from selecting first gear which some times can be a bit clunky there is no more noise from the box than a standard road box. The box its self is quite small by comparison to Tremecs or Richmonds and I guarantee can take all the punishment that can be handed out on the track, the speed of the shift as pointed out by other forum members is only constrained by the opertor. The preffered shift proceedure is to run the engine up to its rev limiter and use the momentary loss of pressure on the box as the engine fluffs a bit (thats an Australian technical term !) to slam it back into the next gear. I have abused my box for the last 5 years and all we have ever done is change the oil.

Hope this is of interest, I have some photos of the gear sets somewhere and will post the when I find them

Regards

Iain

 

[Iain]

Russ,
Where did you get that description of gear shifting from ?
Iain

 

[Russ Noble]

Iain,

Hewland.com go to FAQ's.

Cheers

 

[andys]

My dog box experience parallels those mentioned above. From my experience, they are easiy to drive and smooth when at competition speeds. They can however be pretty clunky when going slowly as evidenced in the video; In the initial stages of that race when the driver was forced to drive erratically and off line, you'll notice how much gear banging was going on. Once up to speed, it was nice and smooth.

Andys

 

[Jono]

Russ,
Sounds simple (or at least less daunting) when you put it like that. I guess like anything else you can be told how to do it a thousand times but no substitute for pratice.

Jac,
Yup, I think it will probably be plenty warm enough, now you mention it. I've got a melted patch on my carpet already just from the current V6 exhaust. My main worry is having a hot air blower for demisting, its quite likely I could need that in the height of summer, especially if this year's has been anything to go by. Anyway, I'll look into alternatives.

I hadn't actually looked at the richmond ratios, Imust pay more attention...

Thanks to all for further advice/reassurance. Might go see what I can find out about these Holinger boxes. From what Fox1 said earlier, I take it that helical and dog engagement combined is a good thing...

The next thing is:, assuming pretty much a free choice in terms of gear ratios (e.g. tex racing), how do you go about choosing? Bearing in mind that whatever I start with will have to be a good all-round gear set as I wont be able to afford multiple sets, at least for a while.......
I know it will depend on rear diff ratio and tyre size, but both of these are still undecided as well..

Thanks
Jono

 

[Iain]

Jono,

I have attached the gear chart from my Holinger to this message, if it does'nt come thru email me and I will send it direct. You can alter the various inputs, diff ratois, tyre dia etc

Iain

 

[David Briggs]

Shifting a Hewland is not hard, I only use the clutch to launch in 1st, clutch is not used again until you are back in the pits, upshifts at redline require a slight release of the throttle and right back on, downshifting is release throttle and as gear lever is sliding thru nuetral wing the throttle to match the engine speed to the track speed of the selected gear, all of this is great fun on the track but would be a huge pain in the keister on the street. As for straight cut gears I think is a little too "Boy Racer" and unneccesary on a street car, sort of like those ultra noisy timing gears.
IMHO
Dave

 

[Jono]

Thanks for spreadsheet. i've got a good little programme called gearcalc which gives you a graph of ratios, tables of speed/rpm, rpm drops between gears etc. Would try and post it up but not sure it will work as it's an exe file. Would it work if I zipped it?

My problem even with that program is that although it will show me attainable speed in each gear etc. I'm not sure if the ratios are practical e.g. will I just spin the wheels in 1st or will it be a complete slug off the line....