I have purchased a proper off-road 4WD for the first time and look forward to doing a lot more road trips with my family. I have loads of questions, but the first thing I want is a roof hatch. Is that a crazy idea or is it a big benefit? What do I have to think about when getting one designed and installed? What sort of budget will I need? Will it affect the value or the safety of the vehicle?
Roof hatches on private cars are not used very often, but they can be a glorious benefit when game viewing or sitting on the roof while watching sunrise and sunset. At these moments, the experience in cars with versus —without roof hatches is incomparable.
If your car is likely to be sold to someone who goes on safaris, a roof hatch will enhance its value, not reduce it. If the hatch is properly fitted, it should not compromise the integrity or safety of the bodyshell or anything else if you accidentally park upside down.
Design and technical competence are important. Where to locate the hatch, how big it should be, the padding to make it comfortable, the lip to keep the rain out, the latches that hold it when it is in place, where to stow it when it is removed, how to lock it down if it is hinged, how it works within a possible roof rack, and the internal cosmetics of the ceiling cloth are all issues to be considered.
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The construction will cut a hole in the roof. This will reduce the rigidity of the body shell, both for tolerance of vibration and strength in an accident. The weatherproofing lip and framing of that hole should restore rigidity (by the correct amount) without the hatch lid. The framing should be both welded and bolted so that in the event of severe impact it remains attached to the main roof panel and does not enter the passenger compartment, in all or part, as an independent guillotine.
I have two 4WD station wagons with hatches that are regularly used on safaris. On group camping trips, I invariably have more passengers than cars without hatches.
One of mine has three hinged lids which fold down onto the roof and are clipped to padded bracing cars. The locations are front, middle and back. The other car has one removable lid (in the middle) which is stowed by clipping to four body mountings on the bonnet lid.
Alternative designs slide away on rails from the padded hole (not having a lip they look smarter and more discreet when shut, but are more expensive and prone to leaks).
Yet other designs have removable lids which slot into frames on or under the roof rack for storage.
For a couple, a hatch above the front seats sounds rational and convenient.
In practice, a hole in the middle (over the “back” seats) is usually better. What you have to decide is whether those using the hatch will stand in the footwell or on the seat (or both).
A hatch at the very back of a large estate is to add capacity. On most 4WD station wagons, the best material for the lid is the cut-out piece of the original roof. It will be stronger, lighter, better shaped and made of higher quality steel than any other metal sheeting you are likely to find (and you have already bought it).
The cosmetic finish of the hatch, inside and out, is important to the retention or enhancement of the vehicle’s value. You need to emphasise that to both the steel fabricator and the upholsterer.The budget? At a guess (only), not less than Sh50,000 for a cheap job. Probably at least twice that and maybe even more for a good one.
Is low-range gearing a rarity or really useful?
How important or useful is a “low range” gearbox for a vehicle used in a wide range of conditions? How does it work and what does it do? Is it purely for “off-road” expeditions?
The strongest men in the world can lift about twice their own weight above their heads with their bare hands, albeit with an enormous effort that makes their eyeballs almost pop out and the blood vessels in their head and neck and body bulge under their skin. But give an ordinary guy a lever, or a pulley system, or gears, and he can lift much more than that weight. Easily.
That huge change in the difference between the “force applied” and the “force produced” is known as “mechanical advantage”. And that is what gears do to the force applied (by the engine) to greatly increase the force produced to turn the wheels of a vehicle.
The lower the gear the greater the mechanical advantage becomes. The single reduction gear in a “Low Range” transfer box lowers all the normal ratios in the main gearbox by about 50 percent.
That roughly doubles the turning force (torque power) at the wheels. Clearly, that change is transformative. It may rarely be needed or used, but there is no doubt that it can often be useful and sometimes essential.
The additional power of super-low gearing not only allows more extreme motoring manoeuvres that would be impossible with the standard gearbox; it also allows less outlandish things to be done with more control, more assurance, and less strain on the vehicle or the heartbeat of its occupants.
An obvious example is a very steep slope or hill. With standard gears, the engine may simply not have enough power to keep the vehicle moving. Any attempt to try could put great strain and high wear on the clutch, among other things. If the shortfall in power is marginal, and the slope is steep but not very long, one solution might be to take a run-up and try to charge up the slope, hoping to reach the top before the momentum energy runs out. Perhaps okay, but don’t be surprised if your passengers opt to get out and walk while you try that.
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But what if the slope, whether off-road or on a track, is littered with sharp rocks, some bigger boulders, lumpy grass tussocks and holes? Charging up could do some gruesome harm to the tyres and suspension and other items under the floor (e.g. you could smash a hole in the sump or break a steering rod). And momentum comes to an almost instant end if hitting a boulder at speed makes the vehicle bounce into the air. When it lands it is likely to be standing still. No momentum.
Now consider the same task using the low range. Double the power is likely to be plenty, even on a slope so steep that the driver will not be able to see the hill beyond. Looking straight ahead through the windscreen, s/he will be seeing the sky). If traction is sufficient, serious 4WDs in the low range can climb hills steep enough to make the occupants feel as though the vehicle is about to fall over backwards. So a slope that was marginally too difficult in the high range can be negotiated in the low range with relative ease, very slowly and carefully if need be, with the engine, transmission, suspension and tyres all working well within their capacity.
Perhaps counter-intuitively, the low range can be equally useful driving “down” a very steep slope; so steep it must be negotiated in a straight-down line at very low speed without using the brakes because uneven braking could make the vehicle slew sideways into a traverse that would risk the car rolling over…and over… with a good bye and good night consequences.
Preventing that insists you use the engine as the brake to restrain speed, and to correct a slew you turn into the skid and accelerate to “drive” the vehicle straight again. In first gear high range, that could be happening at about 20 kph. In first gear low range, it will happen at walking speed, so the slew is less likely to happen in the first place, and any correction is less likely to get out of control.
In the majority of safari circumstances, low range is not used to make the impossible possible. It is used to make the difficult easy. And that doesn’t arise only on expeditionary adventures. As we all know, there are plenty of “off-road” conditions on roads, even in urban areas.