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Hi guys,

I am working on developing a new differential. It will mainly make things simpler when it comes to the design. It'll behave like a 100% locked diff in a straight line and a 100% open diff at turns. The main issue is, if I succeed in developing it, and get it on to a car for testing, the car will not have any engine braking.

I personally don't have much experience in off road driving or driving down the hills. Hence I would want you all to tell me if any of you would actually want a car that does not engine brake. Keeping in mind that the torque distribution will be perfect. This diff wont have any tyre scrubbing as in case of locked diffs and LSD's. Also, no electronics would be needed at all, as in case of E-diffs. This differential will also be cheaper to produce. The biggest issue is the lack of engine braking.

Please help.

Hey,
It's an interesting idea. Could you please quantify the advantages of the differential that you are designing. As in, what is the exact problem area you are addressing with this design and what would be the practical advantages?

To answer your question in one line:
I would not like to drive a car without engine breaking.

The reason being, I assume that if there is no engine braking, that means the engine and drivetrain are practically disconnected everytime you lift off the accelerator. Which would imply that the engine would return to idle RPMs. I do not understand what would happen when I accelerate again. How would the RPMs of the wheels and the engine synchronize?
A disconnection between the engine and the drive train makes the car unstable. Especially when driven fast, while entering corners, this could result in adverse effects on the stability because it essentially means you have one less control mechanism, viz. the Accelerator. However, this might not be applicable to more sedate drivers.

Maybe my assumptions are wrong. Thus, it would be great if you could provide more details.

Hill or offroad driving without engine braking is going to be very difficult. The brake pads will be chewed out in no time.

ujjwalb,
It sounds like an interesting idea. I would love to know more details. Samurai is right though, engine braking is very important in certain situations especially when going into corners, driving downhill and in snow/less traction/off roading situations.

Looks interesting for sure. But we can't really sacrifice Engine braking for this invention as going downhill really needs strong braking force, which is provided by the engine.

If you're design is patented, can you share details?
I've heard of a college project of a differential which uses fluid coupling (eerily similar to a torque converter) instead of Bevel gears. Am I close to the guess?:D

I am not much of an off-roader but here are the reasons why I love me some good engine braking :D and can't imagine giving it away

1. Allows me to shift the weight of the car effortlessly
2. Reduces risk of loss of traction or hydroplaning
3. Allows me to carve corners like a pro
4. Increases the life-span of my brake pads
5. Overall just feels like a crucial factor in maintaining control of my car :)

We had a Ford Zodiac in the 70's that had a lever called Overdrive. This actually activated an epicyclic gear train located after the gearbox. When I used to pull this lever the engine could turn the wheels but you would not be able to turn the engine if you pushed the car, even in gear. So no push starts with the Overdrive on.
On highways, taking the foot off the gas pedal would result in a feeling of going into neutral and the car would coast. Pressing the pedal upto the required engine speed would give a feeling of engagement. FE would shoot up in these trips. However, Overdrive was very enjoyable on highways once you let off the gas pedal after the car has picked up speed.
However, in cities lifting the foot off the gas pedal would give a feeling of sudden increase of speed and one would feel as if someone is pushing the car from behind with the intent of ramming the car in front. Hasty use of brake pedal was required. Very unnerving even on plains. Never used to engage it on slopes.
Don't know why the concept faded out. Maybe because of the cost of the extra epicyclic gearbox. I would love to have a manually engageable Overdrive even today.

posting reply from a friend .

Hello, interesting post - is your differential built around sprag clutches of some kind ?
In any case, as you might have surmised by now, losing engine braking would not be a very welcome idea in the real world.
That said, if you're unable to solve the engine braking problem within your differential itself, it's still not the end of the world.
Maybe you could consider specific or niche applications for your differential - like motor racing, railways, & stuff.
In any case, the very best of luck for your idea :thumbs up

What will happen if one wheel is stuck in a rut / slush while the car is turning? Will the differential be open or closed? What determines if the car is going straight or is turning?

CDM

If you are trying to put over-running clutch (as in the case of a bicycle rear wheel) and trying to comeup with a solution to eliminate the differential, then I would like to inform you that a company called Torsen differentials has already developed it.

I had come up with the same idea long back (I had no internet access then.), but when searched on net I came to know that Torsen already manufactures it.

Having two over-running clutches at the wheel ends helps in eliminating the differential but causes loss of engine braking.

If you have a different idea, nice to know about it.

Hi ujjjwalb,

I have never had any problems with the differential of any car that I owned in last 20 years. So was the case with all my friends and relatives.

So, I wonder, why do you want to develop a new differential? Which problem in the existing design are you trying to address?

Will your proposed design be 100% open even on slight turns, like while changing the lanes? Will it contain any friction clutch?

A number of cars have had a freewheel in their drivetrains, notably Rover, and some 2 stroke powered cars. Do some research to find out user experiences of these, and why these are not used any more.

As for feel, drive an (older) slushbox. (In fact in a few, freewheeling was a 'feature'.)

My feeling too, but since this is can be a new monetisable idea, can't really ask about it!

Regards
Sutripta

The main advantages of this differential would be:
1. Simpler design and production that a LSD
2. The two wheels would still be free to rotate at their own speed when required, unlike a LSD which always creates some dependence.
3. It will be lighter than a LSD. (Can't give an exact figure, but I'm sure it'll be significant amount of weight)

Well, I tried to simulate this condition on my Alto. In fifth gear, the engagement didn't feel sudden or anything that would make me nervous.


No, my idea is not patented. Hence cannot share details. And you're not anywhere close to with your guess. :P

I originally thought about it for my Baja SAE ATV. I spent a lot of time thinking a way to eliminate the lack of engine braking. I think I almost got a solution. Lets see how it goes.

Well, then most of the torque will get transferred to the other wheel.

See the advantages that I have mentioned in this post.
yes, it will behave like an open differential while changing lanes. No, it will not contain a friction clutch.

Thanks for the reply. Will the wheels loose power while changing the lanes?