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View Full Version : front wheel drive- powering only one half shaft



darryl
03-13-2017, 12:26 AM
A few days ago I started wondering about how to add auxiliary power to a front wheel drive vehicle, say electric assist. You could add something to the engine, like replacing the alternator with a combo alternator/motor, but that involves the engine. Apart from that, there are the two half shafts. The idea was to add some kind of custom hydraulic drive that would surround one or both half shafts and power them directly. Two would be more complicated than one, hence the question- could one half shaft be powered this way without having steering or other control issues? Both front wheels would get powered anyway, since they are coupled through the differential.

Stupid idea, possibly. But the question is, would driveability be adversely affected?

J Tiers
03-13-2017, 12:54 AM
I can see it being affected in some conditions....

How about powering the REAR wheels? An electric drive and differential would work fine, and would provide a boost without invasive actions on the front drive.

CCWKen
03-13-2017, 01:04 AM
The differential is key since the speed of each shaft changes depending on the direction of travel. That's what differentials do. Adding to or changing the speed of a half shaft could affect control. Adding assist would have to go in front of the differential or have some pretty complicated control to sense when one shaft turns at a different speed than the other. A note here: Some cars already sense wheel speed changes to control antilock brakes and/or traction control.

JRouche
03-13-2017, 01:26 AM
Like Ken was precluding
. There is not enough speed to make some good voltage. And they are wasting fuel doing the stupid experiment. .I dont have any money. I want to help get these generators to where they are needed...

danlb
03-13-2017, 01:38 AM
Your bigger challenge in adding electric assist to an existing design is to do it smoothly and in a way that will play well with the existing controls and safety features. You might end up with jerking, cogging or failure to work with cruise control, ABS, etc.


What objective are you trying to achieve? Mileage? Emissions? Acceleration? Torque for towing or hills?

Dan

PStechPaul
03-13-2017, 02:04 AM
Some discussion of auxiliary electric power for cars:

http://www.electric-cars-are-for-girls.com/can-i-hook-the-electric-motor-straight-to-the-rear-differential.html

http://www.diyelectriccar.com/forums/showthread.php/rear-wheel-assist-fwdi-worth-iti-9128p2.html

https://rts.i-car.com/collision-repair-news/general-motors-eassist-electric-system.html

http://99mpg.com/Projectcars/mikesinsight/

http://www.abovetopsecret.com/forum/thread894460/pg1

http://www.pstech-inc.com/SHAMPAC.htm (my original idea for DIY hybrid conversion)

darryl
03-13-2017, 03:22 AM
I don't have a particular goal in mind, but perhaps a useful thing would be able to bring the vehicle from stopped up to say 50 or 60 k on the auxiliary power, and also store the reverse of that- decelerating it to near stopped from any normal steady speed. The engine would be left running, and clutched in probably about where you'd be in the second from highest gear.

I still think a flywheel/hydraulic system would work here, since it's not needed to propel the vehicle for any distance. The recoverable energy would be a fixed quantity- even at 100 kph the amount of energy is not a huge quantity and the system could be fairly small and light. The trick would be to design a hydraulic 'translation device' which would be small enough to mount in the limited space available where the half shaft resides (assuming the original idea). Of course in a conventional rear wheel drive you have a couple points where you could access the drive shaft easily enough to add such a system.

If any such thing could be added to a front drive vehicle by using the rear wheels, then some access to driving the rear wheels would be needed. You would likely have to remove the wheels and sandwich a drive 'disc' of some sort between the wheel and the brake drum or disc. It would be better if you could drive an axle directly, but I don't think you would normally have access to that on a front drive vehicle- except for the front wheel drive half shafts. You could always do a mechanical conversion to the rear and sub in parts from a rear wheel drive- probably something with independent suspension so there isn't too much change required in the original suspension.

That's kind of an interesting concept- four wheel drive with the rear wheels using the auxiliary power system, whatever it is.

flylo
03-13-2017, 04:49 AM
How much/long will this be used? If only to get out of being stuck or all the time?

1-800miner
03-13-2017, 08:46 AM
I am not quite understanding your application.
If you are getting the power assist from your existing engine, aren't you robbing Peter to pay Paul?

HWooldridge
03-13-2017, 09:06 AM
I think the closest thing you get to "free" energy is a flywheel, which still has to be started so it's not free either. For example, a hay baler will work off the PTO without a flywheel if the tractor is big enough - but the flywheel helps smooth out the baling and handles clumps. If I understand the original question, you are looking for short term assistance and that is one mechanical way to do it. However, flywheels are generally pretty large - the one on my JD baler weighs about 200 lbs.

A.K. Boomer
03-13-2017, 09:40 AM
A few days ago I started wondering about how to add auxiliary power to a front wheel drive vehicle, say electric assist. You could add something to the engine, like replacing the alternator with a combo alternator/motor, but that involves the engine. Apart from that, there are the two half shafts. The idea was to add some kind of custom hydraulic drive that would surround one or both half shafts and power them directly. Two would be more complicated than one, hence the question- could one half shaft be powered this way without having steering or other control issues? Both front wheels would get powered anyway, since they are coupled through the differential.

Stupid idea, possibly. But the question is, would driveability be adversely affected?

Your probably talking less than 10 ponies so not thinking your going to be getting into a whole lot of torque steer or anything too serious, but your idea should just be shelved for all kinds of reasons most of all complications and extra weight and way to many conversion systems, along with taking power from the engine to then add back into the system after you've converted said power to electricity to then run a motor to then run a hydraulic pump, to then run a hydraulic motor,

Your better off to just focus on tweaking the engines efficiencies - much can be done, running synthetics in all the drivetrain - proper max tire inflation and also hypermileing driving techniques

when gas was 4 bucks a gallon it's how I consistently got over 50mpg's out of my toyota tercel that was only rated 33

big improvement

took an exhaust pyrometer and gauge - an air fuel mixture gauge and a custom made potentiometer tapped into my computers oxy sensor link...

total extra car weight --- maybe about 1lb
complications? done in a day.

J Tiers
03-13-2017, 09:45 AM
It's old, old news. been done for a decade at least.

A neighbor has a hybrid of that type. I forget if it is a honda or what, but it combines a gas and electric motor, NOT the ways a Prius does, it seems NEVER to run on the electric alone. Apparently it runs on a small gas engine, and uses the electric as a boost only.

Seems stupid to me, but apparently it really does work.

A.K. Boomer
03-13-2017, 09:48 AM
Where they shine is in the city - regenerative braking puts city fuel economy almost as good as highway and that's saying something...

A.K. Boomer
03-13-2017, 10:12 AM
I even took it so far as to create a progressive throttle cam, helps you not overshoot your mark and keeps you in granpa mode, still had full throttle if you really wanted to put the effort into it for when you needed it,
this is stock;

http://i146.photobucket.com/albums/r249/AK_Boomer/DSC00377.jpg (http://s146.photobucket.com/user/AK_Boomer/media/DSC00377.jpg.html)

this is modified;
http://i146.photobucket.com/albums/r249/AK_Boomer/DSC00388.jpg (http://s146.photobucket.com/user/AK_Boomer/media/DSC00388.jpg.html)

machining custom values into a potentiometer;

http://i146.photobucket.com/albums/r249/AK_Boomer/DSC00394.jpg (http://s146.photobucket.com/user/AK_Boomer/media/DSC00394.jpg.html)

glowshift gauges installed with ability to adjust mixture ratio's and NOT melt a hole in my pistons... ;

http://i146.photobucket.com/albums/r249/AK_Boomer/DSC00393.jpg (http://s146.photobucket.com/user/AK_Boomer/media/DSC00393.jpg.html)

Joe_B
03-13-2017, 02:11 PM
Stay away from hydraulics, they are horribly inefficient.

RB211
03-13-2017, 02:14 PM
I see where you are going with the differential setup. Rest assured, Toyota already did this with their synergy hybrid drive that is in my second gen Prius. Look it up on how it works.

danlb
03-13-2017, 02:42 PM
Where they shine is in the city - regenerative braking puts city fuel economy almost as good as highway and that's saying something...

That's a common misconception. As one with 15 years of hybrid driving experience, I've learned that the "in town" savings come from the simple fact that most hybrids turn off the gas engine when it's not needed. The regeneration from braking is limited by how fast the batteries can accept the charge without undue heating. I recall that my car will recover (on average) about 10% of the energy via braking. Part of that is because some energy is lost to friction, air resistance, rolling resistance, etc.

Turning off the engine, on the other hand, saves 100% of the energy needed to keep an engine idling. At a 2 minute stoplight it equates to about the power used to travel 1 mile at a steady freeway speed. Where Boomer is hypermiling by turning the engine off, the hybrids do that automatically restarting it as soon as it's needed again. In a 30 minute shopping trip, the engine may be turned off as much as half of the time.

Boomer's disadvantage is that he loses power steering/brakes/ air conditioning when he cuts the engine to cost downhill or to a stop sign. One of the challenges that the early hybrids had to overcome was to develop reliable systems to run all the the systems that normally run off the engine.

danlb
03-13-2017, 02:58 PM
I see where you are going with the differential setup. Rest assured, Toyota already did this with their synergy hybrid drive that is in my second gen Prius. Look it up on how it works.

Are you sure? The last time I looked at the Synergy Drive concept, it used a planetary gear system (ring gear, sun, planetary) with two of the three gear sets being driven (power input) at any particular time. Over simplified, the gear that is not driven becomes the power output.

It's a neat design that allows the gas engine to run at any desired RPM regardless of the speed of the wheels. If the optimum RPM for the engine creates more energy than is needed to move the car, the motor/generator is engaged too in order to store the extra energy.


Dan

A.K. Boomer
03-13-2017, 03:09 PM
Yeah all the above although your recovery on braking should be more than 10%

and my tercel was so light no need for power steering anyways, and still had power brakes up to three different engagements --- and I live in semi-arid conditions so when the AC compressor stops I was still getting cooled off by the residual cooling effect of the evaporator --- not just the storage of the unit, the ice built up in it and then after that the water evaporating ---- im constantly teaching people out here in the MT's to get off the AC on the climbs and then utilize it for the descents,,, it's free braking and AC going downhill and helps save pads but costs dearly going up...

I can get a good 5 solid minutes of cooling effect long after shutting the ac off, good for most of the short local hills around here... and it keeps the evaporator more efficient by removing the ice...

I was into the lower 40's in town driving and I did not even own a hybrid,,, not bad for a car that was rated at 33 mpg highway :p

RB211
03-13-2017, 04:47 PM
Are you sure? The last time I looked at the Synergy Drive concept, it used a planetary gear system (ring gear, sun, planetary) with two of the three gear sets being driven (power input) at any particular time. Over simplified, the gear that is not driven becomes the power output.

It's a neat design that allows the gas engine to run at any desired RPM regardless of the speed of the wheels. If the optimum RPM for the engine creates more energy than is needed to move the car, the motor/generator is engaged too in order to store the extra energy.


Dan

How the torqued is shared between the gas engine and electric motors is no different than if you took a differential, and placed the gas engine on one output shaft, one of the electric motors on the other output shaft, and the traditional input shaft was used as the output shaft, with the second electric motor being used to control the torque sharing, by applying torque to the planetary

darryl
03-13-2017, 08:27 PM
Thought about the original question a bit more- now I realize that if auxiliary power of some sort is driving one half shaft, and the engine is not engaged, the other wheel will get no power- the ring gear will just spin freely. If the engine is engaged, then as long as the engine supplies more torque than the auxiliary power, both front wheels will get power but it will still be off balance. Ok, I see it now- not a good idea.

danlb
03-13-2017, 09:26 PM
Darryl, that's an odd way to end a thread. It leaves no nits to pick!

It was an interesting idea.

Dan

J Tiers
03-13-2017, 10:00 PM
Thought about the original question a bit more- now I realize that if auxiliary power of some sort is driving one half shaft, and the engine is not engaged, the other wheel will get no power- the ring gear will just spin freely. If the engine is engaged, then as long as the engine supplies more torque than the auxiliary power, both front wheels will get power but it will still be off balance. Ok, I see it now- not a good idea.

perfectly FINE idea.

You just have to lock the unused input to direct the torque to the correct output. Easy-peasy, done every day..

MOVE the engine and electric to a first differential that drives the second.

danlb
03-13-2017, 10:33 PM
Darryl, that's an odd way to end a thread. It leaves no nits to pick!


Dan

Aw, I was wrong again. :(

Wirecutter
03-16-2017, 12:14 PM
A few days ago I started wondering about how to add auxiliary power to a front wheel drive vehicle, say electric assist. You could add something to the engine, like replacing the alternator with a combo alternator/motor, but that involves the engine.

Car and Driver did a write up a while back on various hybrid SUVs. One of the parameters "evaluated" was whether the vehicle could move itself on electric power alone. There were a couple that could not, because the only claim to being "hybrid" was that the alternator was modified to provide engine "assist" and a bit of regenerative braking. IIRC, one such vehicle was a Saturn.

I wonder if any billet was involved?

-M

danlb
03-16-2017, 01:48 PM
Addressing Wirecutter's point;

There are several different types of hybrid. What Car and driver was looking for were Mild hybrids (https://en.wikipedia.org/wiki/Mild_hybrid). As noted above, the ability to just stop the ICE (Internal Combustion Engine) when it is not needed will help a LOT in city or stop and go traffic mileage.

Other types of hybrid drive are considered "full hybrid"

1) Serial is where a gas engine drives a generator that runs an electric motor that turns the wheels. This design can also charge a battery pack at the same time when properly designed. The motor is not directly connected to the wheels. The early Hummer used this, as do locomotives.

2) Parallel is where the wheels can be driven by the ICE, or assisted by an electric motor. In some definitions the electric motor can drive the wheels with the engine off, but the ICE is always connected to the wheels. Early Honda designs were this way.

The original volt had two engines and electric motors. One ICE drove the wheels. One ICE turned a generator to extend the electric range.

3) series / parallel is where the wheels can be driven by the ICE or the electric motor or both at once. Properly designed, it can be tuned for higher power OR extremely low emissions OR extremely high mileage. In most cases it's a compromise of the three. Prius is tuned for mileage + very low emissions. Camry is tuned for more power and low emissions. The 887 hp Porche 918 is obviously tuned for power, pure, unadulterated power.

All three full hybrids types can be augmented by adding circuitry to charge from the electric grid. These are "PHEV" or Plugin Hybrid Electric Vehicles. A PHEV can usually drive for a short distance (15 to 50 miles) without using the gas engine IF you have a fully charged battery pack. A new way of computing "mileage" was needed for this type of car, since it uses energy from two different sources. A PHEV that is driven 10 miles a day and charged nightly may never use it's ICE. A PHEV that is driven 100 miles a day may spend 90% of it's time running on gas (if a serial hybrid with PHEV capability).

In short, the term hybrid describes a concept, not a specific implementation. Darryl proposed a parallel system. Jerry's proposal (if fleshed out) might be parallel or series / parallel.

Sorry. I was feeling chatty this morning. :)

dan