Geoff Weeks

If I had to guess, I think it is far more to do with key off draw, which is becoming critical in all vehicle as the electronics become more and more complex. In most cars, for example 50ma was the max figure, I have heard that has be increased on the newest stuff. How that translates to trucks, if key off loads go up, the truck is trying to start with less than full battery. We have reached the limit of what 4 gp 31's can crank in parallel. It becomes cheaper and more reliable (in theory) if you raise the voltage, decreasing the current needed to crank. The choice would be more gp 31's in parallel, adding to weight and storage room or take those 4 gp 31's and divide into two groups of 2 in series. The same amount of power is used, but the highest load (cranking) is a bit more tolerant if the voltage is higher and the current less. It is just like 6 volt can crank a 450 CID engine if all the connections are perfect, but 12 volt will still crank if the connections are a little less than perfect. It get worse in the cold. 12 volt batteries in parallel can do fine in normal temps but can struggle to produce the same current when cold. While job is the same, the ability to make the required current at the lower voltage exceeds what the battery can do when cold.

This made me think that

I think it has come down to how well things have been thought out. One big disaster is: backward compatibility. It is like "feedback carburetion" was. Bandaid on top of badaid until the system collapsed. Once Mfg finely came to the conclusion they couldn't meet requirements with what they always had turned to, then and only then did things get better. Once carburetors were abandoned, and FI took over we went from engines lasting 100k to 2x-3x. Engine life wasn't the thing that pushed the change, it was emissions. 24 volt has always been better in higher power use applications. It was why it was used elsewhere for more that 1/2 a century. 32 volt has been used in marine for a long time, 36 less so. 48 has an operating voltage of over 50VDC and is getting well into the area that you solve one issue and create 2 more. 24 volt is far better than 12 for cranking big bore diesels. What kept it out of this part of the world was backward compatibility. A 12 volt trailer would need retrofitting to be towed by a vehicle supplying 24 volt to the trailer. Back in simpler times a nose box and resistors allowed a 12 volt tractor to tow a 6 volt trailer. When designing electronics, it cost a little more (not much) to make the compatible with multiple voltages around the same range, so stuff like ABS, radios Stab control, engine controls etc, could be made future/backward compatible but have not. The last time we went though a voltage switch vehicles were far simpler. Still VW kept 6 volt until the mid 60's, and 6 volt bulbs (including sealed beam headlights) are still readily available more that 50 years after the last car using them were produced.

You misunderstand me, I wasn't saying it had anything to due with lighting. I only mentioned the lighting in terms of it being the only thing on the buses that WASN'T 24 volt. Voltage has nothing to do with the problems Volvo has created. Some have pushed for higher voltages (Elon!). The higher the voltage the thinner the wire can be for the same "work". It brings other problems like flash over and the need for wider air gap in relays and switches for example. Problems multiply once the actual voltage exceeds 50 VDC, so there is a practical limit on the higher end also. Most problems seam to exist when more than one voltage "system" is used on one vehicle. It come more from implementation (corner cutting) then from the fact there are two (or more)voltages used. Volvo seams to have chosen the route of 24/12 voltage on their trucks to meet an end result, not as the end result. It was their "solution" to implementing some requirement, not the requirement has to be 24 volt.

Back when I was bringing "gray market" European buses to meet DOT spec's the only thing that required 12 volt were Sealed Beam headlights. Sealed beam's were required at that time and no 24 volt sealed beams met the DOT required beam pattern. At that time Motorcoaches (MCI, and others) were also 24 volt, andused either a Vanner battery balancer or some solid state DC-DC were just coming on the market. As others have said in many parts of the world 24 volt in commercial vehicles is the norm. The only today keeping it from being is backward comparability with older trailers and equipment. 12 volt cab accessories could easily be handled by a 24-12 DC to DC converter.

Voltage doesn't effect mutiplexing as far as my understanding. That is done with a digital signal, which is why modules have to be "programed" to the vehicle and can not be interchanged at random between similar vehicles. Either way it is the mfg choice of engineering that had led to the problem, not the voltage nor the EPA (24 volt is not mandated). It is never "we have to make a crappy vehicle" it is "we choose to, because it is cheaper and more profitable".

Most motorcoach's here run 24 volt. It isn't about the voltage or the EPA, it is about the mfg implementation of an ill thought out solution to a power issue. This is all on Volvo.

They used to, IDK anymore.

Pretty much, nothing on the front axle and one S cam on the rear all the way out, and the other???

Ok, I am going to bow out. You seam to be set in your plan, I have expressed my concerns, and what is legal, good luck.

well, I don't see any brake chambers on the front axle. That is not legal either. Time to fully assess what you have and don't. Law is brakes on all axles, functioning and plumbed with DOT approved fittings. Where you are now is no where near legal, and "upgrading" has to take a back seat to getting legal.

Engine is obviously a replacement/reman, but that does help with axle ratio, unless those also have been replaced.

Likely a Big Cam 3, Could possibly be a Small Cam Magnum, I can't see enough of the cam follower covers to know. Would be nice to know axle and ratio. Talk about rode hard and put up wet. A little cleaning would make it sell better.

255 70 22.5 is the smallest you'll be able to fit to what you have there now, Will be smaller than the 9.00x 20s'. I'd still check before I assume. Loaded will make a difference.

Check the clearance 1st. The tires you have on there now are equal to lo-pro 22.5 in diameter, if it hits now, then really the only choice is 17.5 which take a different brake set-up (12.25 x 8 drum) S cam and bracket. Most cases you can't just swap hub and brake spider, as the spider is welded on. Going off road, you know those axles are going to have to pivot to the extreme going over rough ground. Better to know now rather than do the work and get stuck or tear up tires. I've not see a early low boy like that with anything other than 15" hubs (which will take 17.5 tubeless "adapters") Set up with new axle and hub pilot 17.5's would make that a good trailer if the rest isn't all cracked and scab welded.

Those look like 20" rubber not the 15 that most lowboy's from that era had. 9.00x 20, You can mount tubeless demountables on there 295-75-22.5 would be the same OD or you could go smaller 255's which would lower the deck height a bit. I think I'd start by assessing what is there, and how well it is done. If the axles are installed in alignment with the king pin, I wouldn't change. If it was scabbed in and everything is out of alignment, then you are going to have to cut it out to align anyway. Alignment is done by how the brackets are welded on. Everything will be "floppy" until welded, and you better get it right. One looks to be "Propar" axle and one looks to be a axle where the spindle is smaller for the outer bearing. One thing I see in the latest picture that concerns me: Will the tires clear when the suspension is tilted to either extreme? It looks like they will hit when the rear is compressed fully and the front might hit when it is compressed fully. Better to find that out now, rather then after you do all the work. It wouldn't surprise me to learn it had 15" hubs on it from the get go, and someone changed without checking clearances. New axles with 12" brakes and 17.5 tires would be the modern equivalent. I did one axle job on a trailer, measure 4-5 times and weld once!

1st, it looks like they are 12" brakes so new axles will also need to be "low boy" axles, 2nd that is a lot of brackety to weld in for no gain. What is wrong with the current axle? Axle and brake are two different things. That may be an SR-5 but I can't tell from the picture. What size tires does it have on it now?

Coupla things, screw clamps on rubber air lines are not permitted. No way "one is fed from service the other from supply". You've got to get what you have legal before trying to add spring brakes. Without seeing the whole air system, I can't tell what is buggered up and what if anything is correct. What I can see from that one picture will get you shut down in a heartbeat. You've got kinked copper line. I would correct the defects that will get you shut down. I towed many trailers without spring brakes (I was a heavy hauler) over the years. Once the system is correct, you can see if there is enough room to add what is needed for spring brakes. Also need to correct what is wrong with the RH S cam bracket, the push rod is not inline with the slack adjuster. It looks like something with the slack adjuster bushing isn't right, preventing the can as push rod from being properly in line. everytime I look I see more wrong, right chamber fully extended, left chamber fully retracted, what the heck is going on there? Stuck or air to one chamber only?

Heavy equipment trailers were exempt from the spring brake requirement and may be still are. You need to plumb it correctly with an SR-5 valve not just with a relay valve. Look at Bendix's air brake manual for the correct plumbing or leave as is a carry some chalk blocks.

I have a truck with 30 forward gear possibilities. 13 at best are useful. Nothing cool about ratios that for all purposes are the same. No "show-off" potential because it will just sound like you stepped on the clutch and off with no change in engine speed if the gears are overlapping. Map out what the ratios would be in each position and how the rpm would change. In my case with a plumbing change I could add 5 more useless selections! With less than 1/2 the available selections being of any use, adding 5 more wouldn't change that one bit.

Kinda sounds like it was "finding ground" through the ECM circuits?

I was talking about the GMC/Chevy using them, I know they were in other trucks and have seen one (in a D/R) at the ATHS show IIRC.

Steel cable is used on rail cars. I have used chain, but they discourage it claiming it "damages the sticks". rubber belting or steel edge protectors do a good job.

Yep, looks like the docks at the plywood plant east of Bemidji MN or several in (now closed) fire brick plants in MO.

Seams like those docks were made for railcar unloading. Been in a few like that. I was delivering a "drop table" to a railyard (drops the motors and axles out from under the locomotive) . They were insisting that I back in an 11' door when the load was close to 14" wide! Ended up on the old turntable and backed in on the tracks. Drove onto the turntable then rotated and back into the shop.