# Diesel-Hybrid in a '68 Datsun Roadster



## smitty65534 (May 7, 2008)

Hope this is in the right area. I'm in the planning stage of converting a '68 Datsun Roadster to diesel-electric. I currently have a low-hour Kubota diesel (14 hp at 1800 rpm) in a Onan GenSet. My plan is to mount a 48v motor to the bell housing (will have to machine an adapter plate) and a generator to the Kubota engine. Batteries will be located in the trunk.

I am looking for any suggestions on motor and generator. I have a very stong electrical/electronic and mechanical background (35+ yrs in the missile industry). I also have all the workspace needed.

Any and all suggestions will be greatly appreciated. - Thanx


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## ngrimm (Oct 19, 2007)

Welcome! That should be a fun conversion. I actually had a 67 roadster roller a couple years ago but wound up selling it without doing anything to it. They are still one of my favorite cars. It's nice that they have an actual frame so you could take the body off to work on it. Do you know how many watts the generator puts out? I assume you would be putting it in the engine compartment with the electric motor. Norm


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## smitty65534 (May 7, 2008)

Thanks for the return, Norm. This is my third roadster (one 1600 and two 2000s). I kept the last one (bagged and tagged) for spare parts.

The generator, in its present configuration, is a 7.5kw (3 phase). The only part of the unit I will be using is the Kubota engine. I found it a few years ago. It had 1300 hrs on the clock and a bad regulator. I thought about rewiring it for single phase, but decided to find a better use for the diesel.
One of my problems is finding a 48v generator that is reasonable in size to mount up with the Kubota.

Ed


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## ww321q (Mar 28, 2008)

smitty65534 Why 48volts ? I plan on building a parallel hybrid to but at 120volts . J.W.


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## mattW (Sep 14, 2007)

Yeah that was my question too 48V is pretty low, even for a motorcycle. Are you just using it for low speeds?


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## smitty65534 (May 7, 2008)

A few reasons for the 48v. 

A 48v system was used back in 1979 with a similar system. It was in an Opel GT and used a two jet aircraft surplus generators, the small one for charging and the larger one as the motor. It used a small Briggs & Stratton gas engine for charging. This vehicle, if I remember correctly, was capable of a max speed of 90 mph (unsustained) and cruising speeds in the 70 mph area. Fuel efficiency was in the 75 mpg area. The original article, including update, is in the Mother Earth archives.

Another reason is to lower the overall weight. My diesel (less radiator & etc.) weighs in at 295 lbs. I expect the motor to be approximately 140 lbs and the generator to be somewhere below 90 lbs. If I use a 48v system, four main batteries will approach 300 lbs and the aux battery will be about 40 lbs. Total dry weight should be 2200 - 2300 lbs.

I am strictly a begginer in this field and will gladly accept other suggestions. I am very familiar with DC motors in general but have never attempted an application of this type.

I am going to try to maintain the cost of this project under $7,000 (excluding the donor vehicle and the diesel, which I already have). Again, I am open to any and all suggestions.

Thanx - Ed


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## smitty65534 (May 7, 2008)

One other item.

This is not intended to be a parallel hybrid. The diesel will strictly be used for charging the drive batteries and providing additional current under heavy loads.

Ed


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## mattW (Sep 14, 2007)

Generally speaking voltage is usually the best indicator of the power and top speed of vehicles. Take a look at the EV album and compare the voltage and top speeds of various vehicles. 48V is just going to mean you are pulling a huge amount of amps. Even with 1000amps (a lot) you are only going to have 48kW (64hp) of power. It would be better to go with lots of smaller batteries then 4 huge ones. I really doubt some of the claims about that hybrid. I have seen the article and don't find it that convincing.


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## smitty65534 (May 7, 2008)

I understand everything you are saying. The numbers I had come up with were more in the 400 amp (max) range. Using that number comes up with 19,200W. I figured a 6% loss in the transmission (5 speed) and 15% loss in the rear end. Total to the rear wheels should be around 22 hp. I know that won't set any speed records (by any imagination), but actual hp required to hold 60 - 70 mph in this vehicle should be 15 to 18.

What kind of motor and batteries would you suggest? I have researched quite a few and find they all have their pros and cons.

Whatever is selected will be mounted to the bell housing and will go through the original clutch assembly. Initial "locked rotor" condition causes an extremely high current spike, and in many cases, can cause failures. Initially bringing the rpm of the motor up and then engaging the clutch, may eliminate a few problems.

Thanks for the input. Every bit of information is GREATLY appreciated.

Ed


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## ngrimm (Oct 19, 2007)

So do you loose a lot in efficiency when using a 110/220 volt generator since I assume you would need an inverter or charger to make it work on dc? I haven't seen many dc generators. Here is a generator head from Harbor Freight: http://search.harborfreight.com/cpisearch/web/search.do?keyword=generator+head&Submit=Go


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## smitty65534 (May 7, 2008)

Generators are, by definition, DC. The older dc motors (like a starter on a car) become generators if you turn them with another source of power. Until the late '60s, all cars had generators (DC). The alternator was then introduced which produced AC and had to be rectified to change to DC. Some EVs use this type of motor. An advantage is that it will generate power when decelerating (stopping or going down a hill).

Ed


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## dfwheelman (May 15, 2008)

smitty65534 said:


> Generators are, by definition, DC. The older dc motors (like a starter on a car) become generators if you turn them with another source of power. Until the late '60s, all cars had generators (DC). The alternator was then introduced which produced AC and had to be rectified to change to DC. Some EVs use this type of motor. An advantage is that it will generate power when decelerating (stopping or going down a hill).
> 
> Ed


actually i edited this, at first i thought only dc motors had regenerative abilities but i was wrong. either can be configured this way.


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