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VoltsWagon
A DIY hybrid concept for your old truck. | |
At a certain point in every DIY mechanics career there is the moment when you look under a conventional soild axle 4wd cab-and-bed on frame truck and realize the huge quantity of wasted space found under the bed. To the experienced Dr Wrenchenstein this space is like sweet candy, an invitation to start
fabricating a project of some sort.
In a recent posting on the HB a novel use of this truck hinterland was proposed. Since it clearly needed to be aired to the wider public I will flesh out my vision of it here.
The idea is to convert a such a conventional truck into a hybrid drive train using a VW aircooled engine mounted in the rear and an electric motor mounted in the front. My rationale is that this layout minimizes the degree of fabrication while proving all of the benefits of true hybrid drive train.
Steps:
1)Remove engine, transmission, radiator, driveshaft, rear axle.
2) Weld battery trays into the engine bay.
3) Install drive motor(s) on front axle
4) Fabricate a solid beam axle to mount the rear hubs from the VW independent rear suspension in such way that it mates to the stock suspension of the truck springs and shocks
5) Mount the VW engine behind the rear axle in the space between the frame rails usually occupied by the spare tire
6) Extend cable shift and other engine controls to the cab of the truck and mount.
Ok so how do we make this work ? K.I.S.S.
The truck is driven as a normal manual truck but with some small changes. There is no need to de-clutch when you come to a stop because the EV motor can launch the truck from a dead stop, spinning up the gas motor from a dead stop lowering emissions and increasing stop and go economy. The truck may be driven in neutral using the throttle but disabling the engine. The truck may be driven in any gear utilizing as much or as little engine assistance as needed. (short of over reving the motor). When braking regenerative action is used for light breaking, in conjunction with conventional brakes for heavy breaking with an adjusted brake bias valve. Heat,brake vacuum and limp home power is provided by the VW engine. Steering assistance provided by an electric pump. Minimal fabrication. Minimal addition of expensive ingredients. No expensive computerization. Just a cheap, effective 4wd hybrid truck.
EV calculators
http://www.evconvert.com/tools/evcalc/
I used them for this idea. Armchair EV anyone? [WcW, Apr 03 2009]
De Dion Axle
http://www.carbible...spension_bible.html
scroll down about 2/3 for the section on the De Dion axle [discontinuuity, Apr 04 2009]
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I'm actually getting some measurements today... |
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far be it from me to criticize one of my own ideas :D (though filling the rails isn't my original idea btw, I read it somewhere) but why don't you just drop a smaller engine (doesn't have to be a flat-4) into the front and put batteries between the rails ? why put the engine in the back ? |
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I don't think you'd have limp-home capability in a loaded truck (or uphill in an unloaded one) with a full VW Beetle powertrain if you ran out of electricity... and I still think 100lbs of engine welded to a beam axle will just result in your rear end bouncing solo down the road after a few potholes. (I'm still a bit poleaxed from the idea of using a VW engine though, I just don't think the rest of the VW drivetrain would be up to it) |
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(and now you've got me contemplating bud's gas-guzzler pickup he hinted that he wants to trade for my sedan (both are pretty ancient, currently in non-driveable condition but neither would require much work to get rolling again)) |
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The front drive EV rear drive ICE concept works well because it allows for the retention of the conventional front suspension and steering setup. A FWD swap would make sense but it would require extensive fabrication. Eliminating the truck transmission and transfer case, radiator and heavy engine itself should help offset the added weight of the batteries while eliminating much inefficiency. The use of a lightweight drivetrain like the VW engine and transaxle placed in the rear should improve the handling of the truck. Having the EV drive system in the front also allows for maximal recharge loading in lieu of conventional braking. The beam axle mated to a full floating differential is the best compromise for strength and handling. No the engine would not be unsprung in this scenario. |
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Although the thought of simply placing an EV motor on the front axle and running a RWD drivetrain makes a lot of sense. This gets bonus points for being extreme. |
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Apart from the ability to run a beetle/porshe ICE drivetrain in the rear, I'm confused as to why the engine needs to be in the rear. |
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Surely there's a smaller engine in the family for your truck lump that can bolt straight onto the current gearbox. Assuming you have a locking central diff, you can simply remove either the front or rear prop shafts and place the electric motor in it's place. Add a gearbox input handbrake and you've got all the hybrid you like: |
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Regen braking with a locked diff
EV with a locked gearbox (drive through diff)
If you want you could have an assist motor on the redundant axle for assist work. |
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I suppose the simpler option would be to simply weld up the diff and only put the motor on the spare axle, possibly with a smaller 'regen + assist' motor on the spare output of the transfer case. |
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much would need changing to allow a 4wd truck of the conventional design (ford, chevy, dodge mid 80's toyota) to operate as a full time FWD. The fuel economy when driven this way would be terrible and you don't reduce the weight of the vehicle at all. You might as well retain the entire drive train and add a supplemental electronic motor. no, the good thing about this setup is that it allows you to use a full electric conversion under the hood (a "kit") while also having the benefits of hybridization. I suspect that you could keep the weight of the entire conversion, engine batteries and all, within 500 lbs of stock and have a vehicle that can travel 50 miles full electric empty, and move a 1/2 ton load. |
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well I'm not going to reiterate that your backend is gonna have a life all its own as it bounces off merrily into the distance as soon as you lose your electrics (okay maybe I am) |
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//why the engine needs to be in the rear//
pickup trucks have horrible driving characteristics in wet/snow conditions when they're not loaded up because they're RWD; putting the engine in back allows for a bit better handling when unloaded, also in this case the more powerful engine is still driving the rear-wheels (which is as it should be). In my case I want it like that to keep it simple and not have pipes and conduits crossing underneath the cab. |
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[WcW] I didn't consider not putting a motorgen in the rear with the ICE engine as you (apparently) are, hmm.... |
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I'm still confused as to your axle arrangements: the VW drivetrain is a single unit so dunno how you're going to keep it from being unsprung with a solid axle. |
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Adding enough batteries for a 50 mile range (I wasn't aware the battery/motor/controller can be bought as a 'kit') isn't gonna add weight? |
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If the VW powertrain struggles to pull a camper up a decent hill, how's it gonna cope with a 2-ton truck (plus load)? |
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I guess I'm underesting your emphasis on the EV side of this conversion, are you wanting Chevy Volt style usage? |
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ok so imagine this, we take the vw transaxle, fully independent rear and instead of adapting it to the truck instead we weld the hubs to a dead axle, a beam. This beam moves independent from the transaxle but within the range of the axles and CV's. behaving much as the solid live axle did on the truck. Since we are removing the drive system of the truck and replacing it with an EV system I think that we can swap about even for weight on the front end. A VW 1800 FI engine and tranny weigh in at around 300-350 lbs with only a slight offset for the beam/axle swap. Using some calculators from an online EV site I suspect that this would function best as a 100% hybrid with the gas engine always in play. If you went all battery your useful trip distance drops to around 10 miles unloaded. You would always have that option if you opted for it (the driver manages the degree of hybridization) but I suspect that the use of a 26 HP 144v drive unit mated to a 85 hp vw engine could scale most hills. This idea isn't for someone who wants to haul their boat to the river, it's more useful for a utility, or delivery, truck in the roundabout category. |
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Does the panhard(beam) or half-axles telescope in any manner? |
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the axles behave as they did in the vw (up and down with some variation in length), the beam mounts to the spring shackles and shocks. |
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Sounds like you'll have reduced unsprung weight on the axle (+), but would it need some special half-shafts (-)? I doubt the track on the original VW is as wide as you'll need to span the truck! |
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You've earned a bun, but I'm still concerned it's gonna be pretty weedy. |
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Electric truck conversions are fairly common, since as you noted the chassis has plenty of room and can take the extra weight of batteries. I have not heard too much about hybrid pickups, though. |
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As others have said, I think that it would be easier to go with the stock truck engine in the front rather than try to use a Volkswagen engine/drivetrain. You would save a lot of fabrication and other trouble, and it would be much easier to use the stock heater core with a water cooled engine than try to make cabin heat with an air cooled engine. It would be fairly simple to ditch the transfer case and mount the electric motor in its place to drive the front axle. The problem of weight distribution could be solved by mounting the batteries in the back section of the chassis or in the bed. |
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If your heart is set on using a VW drivetrain, I think what you want is a De Dion axle (see my link) for the back. This is essentially a solid beam axle with suspension like a normal truck axle, but with the differential mounted on the chassis and connected to the hubs with halfshafts and CV joints. One hurdle you might need to overcome is adding some kind of telescoping connection in the halfshafts to allow the axle to move up and down, but I believe that modern CV joints have some provision for this already built in. |
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All in all, not a bad idea. I've been thinking about a similar idea, using a Toyota MR-2 (which has the engine in the back) and adding an electric motor in the front. Maybe I'll have to write that up now. |
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is there a FWD car that you can swap for on the MR2 chassis? That sounds like a pretty substantial project. I would think that this would be a perfect project for a junkyard owner with VWs and gutted trucks to choose from. You are correct that the De Dion is the name for a this sort of axle but that isn't going to help most people, especially since this would be a fab part. |
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