Adventure EV

Weigh In

by on Nov.05, 2009, under Design, EV Land Rover, ICE

I need to figure out how much the Rover weighs prior to its conversion to electric power.  That way, I can know, roughly, how much it will weigh post conversion, which will give me some idea of its potential performance capability.  So it’s time for a weigh in!

I don’t have access to a truck scale, so I borrowed this idea for weighing a vehicle at home on a typical bathroom scale.  This method should be fairly accurate.  Even if it isn’t absolutely correct, if I use the same methodology for weighing the truck post-conversion, I will have a good idea of how things relatively compare.  But let’s see how I did.

I’ll be weighing each corner of the vehicle and then adding the results together.  This gives me the added benefit of seeing the weight differences on a per corner basis which can help guide battery placement to even things out, if necessary.

If I simply place a scale under one corner of a 3000lb vehicle, the scale would break trying to handle, potentially, 1000 lbs of weight.  So, I’ll use a lever system to scale the weight down to something reasonable.

How does it work?  A board, forming a bridge, acts as a lever between the scale and another anchor point on the ground.  The wheel sits on the board, and depending on the wheel’s location between the scale and anchor point, the weight measured at the scale changes.

Place the wheel at the scale end of the board and the weight of the truck sits almost entirely on the scale itself. The scale will reflect the entire weight of the corner.  Place the wheel at the other end of the board, at the anchor point, and the weight of the truck sits entirely over the anchor point, causing the scale to measure nothing.  Split the difference, positioning the wheel halfway between the scale and the anchor point, and half of the vehicle’s corner weight will transfer to the scale, while the other half goes to the anchor point.  In this case, multiplying the result measured by the scale by two will reflect the correct corner weight.

500 pounds is still too much for my cheap 300 pound-capacity bathroom scale, so I will use a 4x multiplier, by placing the Rover’s wheel 25% of the way from the anchor point.

Illustration of the weight theory

Illustration of the weight theory

First, I took a 2×6 piece of wood, four feet long, and marked it one foot from one end.  The board was suspended between the scale on one end and another piece of 2×6, my anchor point, at the other.  The setup was positioned so that each tire I measured would sit on the one foot marker near the anchor end.

Setup of the weighing rig

Setup of the weighing rig

For the measurement to be accurate the entire vehicle has to sit level with all four tire contact patches at the same height, otherwise the raised corner would receive more weight.  The discrepancy is not insignificant.  In my testing there was a 100 pound difference on one corner when I didn’t raised all the wheels to the same height.

All four tires raised to the same height

All four tires raised to the same height

When all measurements were taken I came up with the following (all measurements in lbs):

FL – 245  X 4 = 980 / FR – 184 x 4 = 736

RL – 176 x 4 = 704 / RR – 174 x 5 = 696

For a total weight of 3116 lbs and a 60/40 front/rear split.  Interesting to note the 250 lb heavier left front.  My only explanation is, the steering hardware, braking system, clutch, alternator, manifolds, exhaust system, and carburettor are all biased towards the left.  The suspension springs on the Land Rover are sided; the left side is stronger than the right.  Enthusiasts say this is to counteract the weight of the driver, and while that may be true, it may also be to counteract 250lbs more vehicle pounds on the left side!  The weight balance left to right at the rear is just about equal.

Multiply by four to get the real weight

Multiply by four to get the real weight

Not bad for a small SUV.  Of course, it does have an all aluminum body and not much in the way of creature comforts, carpeting, or insulation.  But it’s a good start.  That’s with two fuel tanks, as well.  Although they’re probably only about 1/4 full at the moment.  I wonder if I can get the rig down to 2400 lbs with all the ICE stuff gone?  More on that in  a different post.

How do my measurements compare to official published specs?  A stock 1971 Series 2A 88″ Station Wagon model is listed at 3281lbs, while a stock Base model lists at 2953lbs.  So I’m right in there.  My Rover is technically a Station Wagon, but I’ve added a larger rear fuel tank, stripped the rear of seats, and have a lighter than stock exhaust system.  I’m happy with 3116 lbs, at the minute.

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