Converting a heavy-duty bus/coach/truck into a motorhome (page 94 of 161)

It's the servitude, meaning it stays on as long as the bottles aren't completely full (i.e., as long as you don't need to drive, so you can fully charge your braking system). You can start moving once the pressure gauge hits 4 bars.

Otherwise, Shanko, your ad can only be posted here if you want to trade your motorcycle for a pair of S53s, lol!

ok

Okay + 😎

I wish you all my best for 2007—may the projects in progress wrap up with a shiny motorhome registration, and for the dreamers, may they turn their dreams into reality!

Hi everyone, First of all, I wish you all a happy and prosperous 2007, good health (that’s the most important thing), and lots of travels with buses, RVs, and other vehicles.

And I hope your construction projects come to fruition with the approval of the relevant authorities.

Happy New Year and good health!!!!!

For your info, I changed the front axle ratio on my differential 3.7:1 (originally 4.65:1), and despite the 4-speed automatic transmission, I’ve reduced fuel consumption by 3 to 5 liters per 100 km. My top speed has also increased from 95 km/h to 120 km/h, but the best part is being able to drive at around 95 km/h at just 1700 RPM.

Hey François,

It’s a great idea if the mechanics can handle the longer pull—all upside! 😉 But how much does this kind of modification cost?

What do you mean by "méca"? Apart from the wheels turning slightly faster, there’s no issue—the longer transmission ratio reduces the torque on the components!! (You’ll also need to recalibrate the tachograph, which is very simple with an electronic one. For a mechanical tachograph, you’ll have to adjust the transmission ratio of the cable.)

For the cost, budget between 500 € and 1500 € for a used front axle from a scrapyard or garage, and the replacement should take about a day (depending on available space and tools).

In my case, it was a Mercedes axle, but I still had to modify the differential housing (banjo) because this axle ratio wasn’t designed for buses.

Cheers and happy holidays

By the way, I’m not sure how this is going to work for us now with the removal of the 110 km/h limit—since we’re in category C, we’re now limited to 90 km/h instead of 100 km/h like before?

By "mechanical setup," I mean the entire drivetrain designed for a shorter gear ratio, so less effort (which is the opposite of what you mentioned). The ratio is actually longer, so the effort increases—the vehicle "pulls" longer, climbs more slowly through the gears, and the transmission strains more on hills. At the same speed, the wheels turn the same, but your transmission turns more slowly at that speed. (In racing, we use shorter gears to accelerate faster and gain torque and horsepower, but you quickly hit the speed limit.)

Try this experiment: put a wheel at the end of a broomstick, spin it with your hand, then swap it for a smaller or larger wheel—you’ll immediately feel the difference in required force.😎 Some undersized vehicles (I *think* 😇), like the famous ex-Unic-Heuliez military trucks (same front as my GX) fitted with larger rims and tires because the originals are no longer made, struggle a bit and strain (I *think* 😇) due to the increased rolling surface, including clutches that burn out... I *think* 😇.

Okay, a better example where I don’t need to say "I think" to avoid getting roasted...

My dieselized Willys Jeep: I upgraded it to 700x16 tires (careful, experts say it *can’t* be done 😄—so don’t try this) instead of the stock 600x16. It’s a bit like your situation, but without modifying the transmission. I thought I’d gain top speed (which is STUPID for a Willys...), but it was actually to lower the engine RPM. That part worked, but the engine strains more. Instead of using less fuel, I use more because you have to "pull" harder on the engine to accelerate, stress the clutch and gearbox longer, and the TOP—I LOST top speed, 😠 the engine struggles and doesn’t rev as high... Dumb, right?🤪 To top it off, I blew the engine (head gasket and warping in a row😕) on a 5km straightaway😐 at full throttle. There’s the long explanation. My solution: go back? Never!😏 I’m putting in a bigger engine! Yeah, I know—I’ll break the left rear driveshaft, the diff, and the gearbox, but I’ll replace them with "reinforced trial-spec" parts. It’s fun for me😄...

For your coach, don’t worry too much—you’ll pull longer at startup, but you don’t need a lead foot. Let it struggle on hills; you’ll only save on fuel. Especially since the cost seems trivial compared to the liters of diesel saved per 100 km (good for the planet!)

I really don’t want to contradict you, but a short or long axle ratio doesn’t change the power. Plus, the torque at the wheel is inversely proportional to the wheel’s rotational speed—so the longer the ratio, the less torque you get (otherwise, why would planetary reducers in the wheels exist???)

And besides, I’m not worried because I’ve already driven 4,000 km with this axle ratio

Hmm, it's complicated. Technically, whether a driveshaft is long or short doesn’t change the engine’s actual power output. The engine doesn’t produce more or less horsepower. That said, the power delivered to the wheels will be greater with a shorter driveshaft. For example, when I dyno-tested my NSR, the power varied depending on the gear ratio—that’s why we calculate wheel horsepower by inputting the gear ratio and wheel size parameters. The engine will handle the load more easily with a short driveshaft than a long one. A longer driveshaft demands more force from the engine, which increases fuel consumption—unless you’re cruising at a steady speed. Here’s a (not entirely accurate) example: 😛 if you’re doing 2000 RPM at 90 km/h with a short driveshaft vs. 1700 RPM at 90 km/h with a long one, you save fuel. But to reach that 90 km/h in the same time, consumption actually goes up. Fortunately, not by *that* much, which makes the long driveshaft more economical for "long-distance" transport.

I was chatting with a bus driver buddy about city buses. Many consume 50 L/100 km, which is huge—some blame the short driveshaft, but consumption would actually be even higher with a long one because you’d still need the same acceleration but wouldn’t cruise at high speeds for long, so fuel use would increase. Anyway, I’m no expert, and given the time and the "empty bottles" on the table, I might be wrong🙂 Cheers, Pierrick

The fact that a long wheelbase makes the engine work harder on slight inclines and when accelerating means you’ve got to watch the lower engine block, since that’s the part that struggles—and in the long run, that’s not good... At the same time as the wheelbase change, you should add an extra gear at the transmission output, and that really helps...

Hi there,

Thanks François for your reply. I now have some questions about regulations—could someone remind me of the minimum height for berths? And regarding homemade benches, what’s needed to certify them as road seats, apart from the armrest for two seats? (see plan)

Have a great day, everyone!

Boniz

Hey there!

How's it going with your project? Making good progress?

Show us some photos of your bus here!

hey everyone check out TF1, there's a show at 1:30 PM about motorhomes later jose

hey jose

I’ve been waiting a week for this show, thanks anyway jose😉

Uh, there's some confusion about my terms when I wrote: "(in racing, we use short gears to accelerate faster and gain torque and horsepower, .....)" I didn't mean I was increasing the engine's power or torque, but rather the vehicle's overall performance because as shanko pointed out, the real power delivered—the useful one—is at the output. Example: for an agricultural tractor, the power delivered is specified at the power take-off.

But anyway, we're getting into terminology, calculations, and gear ratios that can make your head spin. So it's better not to go too deep into it, or take it to PM, otherwise we'll bore everyone just like with those posts about the 12V/24V electrical power ratio in coaches.😕

I have a knack for bringing up brain-teasing problems😄😄😄 I'll be more careful next year😏

Happy cool end of the year!

Fun and nice report on today's American motorhomes...

GX47

marrant et gentil le reportage on today’s American RVs...

GX47

What’s really depressing is seeing how they can tow a pickup with a towbar using their mobile homes, and that pickup itself carries a huge motorcycle in its bed. 😏

Otherwise, it's silly—I didn’t turn on my TV fast enough and missed that 1:30 PM show. Oh well, I’ll just have to record it Tuesday at 2:10 AM (hoping I find a blank tape and it works).

I totally agree with you on that! :) Except I actually like the 12/24 setup, but when it comes to axles, I don’t get it AT ALL. Unlike what I thought, saying "I’ll put my coach’s tires on my car and go faster" (okay, exaggerating a bit...) doesn’t do anything. So raising the tires by 10 cm doesn’t help at all?

Little practical problem:

I stretch a cable around the equator—you can easily find the circumference on Wikipedia. If I increase the length of this cable by just 1 meter, as you all know, gravity will come into play, and if it stays taut, it will lift. How far will it rise?

Play along, it’s fun.

Think about it before drinking champagne. The first one to send me the answer in a PM (exact to the hundredth) gets a glass of bubbly from me, and happy New Year to everyone!!

Hey there..!

My camper’s coming along little by little.. we’ve almost finished welding the bars, I’ve attached some photos. I’ll buy my metal sheets next week, so not too much work until then. I’ve got more manpower than supplies right now..🤪..! For those who like calculations: I wanted to get an idea about the electric setup. If I add a (small) fridge, a TV, DVD player, a computer, all running on 220V, plus lighting and pumps on 24V, how often will I need to start the generator to recharge the batteries? Big batteries, by the way..

Have a great evening, everyone..!

Boniz

Love that motorhome show on TF1! 😊 It really makes us dream and end the year on a high note 😇😜