[jsensiba]

I have a 2005 Trailblazer with a great body and interior, but drivetrain issues. I know a lighter weight vehicle would be preferable, but I'm wanting to build something for trail adventures, etc. I'd like to make it a multi-fuel vehicle, so a PHEV that can be plugged in or ran on liquid/gas fuel would be great.

What I'd like to do:

Step 1: Start with building a 4WD EV, limited range, possibly 30-50 miles. It's currently 2WD, so I'm not sure what the best way to achieve this is. Drive the rear axle with one motor, then direct drive the front wheels? Put a 4WD Trailblazer front end and use two motors? One motor for each wheel?

If that's going to become too complex, I can just go ahead and go with RWD, but I'd prefer to drive the rear axle directly instead of messing around with the iffy 4L65 transmission.

I'd like to have J1772 6.6kW charging, but want to see what options I have for DCFC, if any, for homebrews.

Ideas would be appreciated for step 1.

Step 2: Add a 30kW turbine genset either under the hood or in a hitch-mounted module to save weight on local battery-only runs. I've found such on ebay for $5000-6000, some previously used as I envision.

Step 3: Eventually add a trailer with a portable foldup solar charger of some kind. Haven't thought about this one much, and may never get this far with all of the work in the previous steps LOL

Thoughts?

 

[jsensiba]

Parts I've considered thus far:

Siemens 3 Phase motor:
http://www.evwest.com/catalog/product_info.php?products_id=257

Rinehart Controller:
http://www.evwest.com/catalog/product_info.php?cPath=1&products_id=258

Used Tesla-Smart packs:
http://www.evwest.com/catalog/product_info.php?products_id=329&osCsid=eg1e4ljgrv7m26ni4ndbhkgo50

Does this motor need more reduction than a rear-end would provide, or can it be coupled directly to the rear-end? If not, what are my options for using the GM 4L65E for reduction? Does multiple gears give better top speed?

 

[brian_]

Parts I've considered thus far:

Siemens 3 Phase motor:
http://www.evwest.com/catalog/product_info.php?products_id=257

...

Does this motor need more reduction than a rear-end would provide, or can it be coupled directly to the rear-end? If not, what are my options for using the GM 4L65E for reduction? Does multiple gears give better top speed?

The EV West web page says that this motor is tested to produce 221 lb-ft of torque. That's substantially less than the peak torque of the stock six-cylinder engine in a Trailblazer, and without the transmission is like driving in 3rd gear of the transmission (which appears from Wikipedia to likely be a 4L60-E, rather than a 4L65-E). That seems unlikely to be satisfactory, since at low speeds the stock vehicle would multiple the engine's torque by 3.06 in first gear, plus additional multiplication by the torque converter.

The motor can run to 10,000 rpm, so it could use substantially more gear reduction than provided by the Trailblazer's rear axle and still not over-rev at reasonable highway speeds... without needing multiple ratios. Common EVs such as the Nissan Leaf use motors with a similar top rotational speed, and a single reduction ratio of about 7:1... compared to the Trailblazer's rear axle ratio which is probably something between 3.42:1 and 4.10:1.

 

[brian_]

Step 2: Add a 30kW turbine genset either under the hood or in a hitch-mounted module to save weight on local battery-only runs.

I assume that this is a Capstone C30. I'm trying to imagine the genset, with intake filtering and exhaust muffling, plus a useful size of fuel tank, plus whatever else you need that fills a large cabinet in working installations of these things, all contained in a hitch-mounted box... and it's not a desirable thing to have on the back of the vehicle. Maybe in a trailer?

 

[tylerwatts]

Hi jsensiba
Does the 4wd trailblazer come with a high/low transfer case? You could probably get an aftermarket transfer case with appropriate ratios for off road/city and highway driving with only the 2 ratios and use just 1motor hidden in the transmission tunnel giving more battery/generator space up front. Only caveat is trying to get a transfer case happy to shift while moving, ideally with synchros for smooth engagement. That might be a challenge, but there's alot of choice in this market so you never know.
This would be simple and effective and more affordable.

Cheers

Tyler

 

[brian_]

Does the 4wd trailblazer come with a high/low transfer case? You could probably get an aftermarket transfer case with appropriate ratios for off road/city and highway driving with only the 2 ratios and use just 1motor hidden in the transmission tunnel giving more battery/generator space up front. Only caveat is trying to get a transfer case happy to shift while moving, ideally with synchros for smooth engagement.

It looks like the Trailblazer comes with the NVG 226; yes, this has two ratios. It's a reasonably nice unit with clutch so it can engage 4WD automatically when left in the right mode (Auto 4WD), but has no centre differential so any time the front drive output is engaged, it is locked to the rear output speed.

I like the general idea, which is proposed each time that anyone discusses a 4X4 conversion, but I don't think shift-on-the-fly is the only problem. With most transfer cases, the low gear can only be used in 4WD, with the front and rear output shafts locked to the same speed; that's fine in many off-road situations, but nearly useless on-road. In the NVG 226, Auto 4WD only works in the high ratio.

For shift-on-the-fly, apparently some transfer cases do have synchronizers; for instance, apparently the manually-shifted NP271 does not have synchros and is not to be shifted on-the-fly, while the NP273 is essentially the same transfer case with an electric shift motor and a synchro ring. Unfortunately, this is likely only for engaging 4WD, not for shifting gear ranges.

While having two ratios seems good, the "high" ratio (which is normally direct, so 1:1, as it is in the NVG 226) is higher than needed, and the low ratio (anything from about 2:1 to about 4:1) could probably be used all of the time. The 2.69:1 low ratio of the NVG 226 would probably be a great single gear, combining with the 3.42, 3.73, or 4.10 final drive to produce an overall ratio of 9.19, 10.03, or 11.03:1.

With a typical stock tire size of 235/75R16, which turns 697 revolutions per mile, 60 mph would be 697 RPM. That would be 7687 RPM at the motor even in low gear of the stock transfer case (2.69:1) with the shortest axle ratio (4.10:1), and lower motor speeds with the other axle ratios. If the motor can run to 10,000 RPM, that would be a "redline" of 78 MPH. Since the motor can produce about the same continuous power at any speed from 5,000 to 10,000 RPM, if the top speed is power-limited changing moderately from this gearing wouldn't matter; if you gear taller you run the motor at lower speed and higher torque, and if you gear lower you run the motor at higher speed and lower torque.

It looks like the NVG 226 uses a single control motor and cam to control both engaging low gear ratio and engaging the 4WD clutch, so it's probably not possible to find a position which would cause it to use the low ratio without engaging locked 4WD. This is typical of transfer cases.

Ideally, a transfer case for this application would:

• allow engaging low gear without engaging locked 4WD (which likely means a manually-shifted box with an interlock removed), and
• would have a centre differential so 4WD could be used on dry pavement.

If the stock NVG 226 could be - even permanently - set in low gear with auto 4WD, it would work. I hope the gearing can stand the input spinning much faster than the stock engine ever runs...