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Semi Trucks in USA - why no XXL large units

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Semi Trucks in USA - why no XXL large units

Old 1st Jun 2018, 04:56
  #21 (permalink)  
 
Join Date: Jul 2003
Location: Oz
Posts: 815
Had a ride in my mates brand new B tripple the other day. 650 Hp and 2400 ft/lbs or torque coupled to I think, a 24 speed auto geabox, disc brakes on every axle. This is a state of the art truck. He grosses way over 90 tons. he reckons that his truck is way more pavement friendly that a traditional semi as he has lots more tyres to spread the load and that his hp would get him over any mountain in the USA, including the Eisenhower tunnel in Colorado.
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Old 1st Jun 2018, 06:01
  #22 (permalink)  
 
Join Date: Jul 2013
Location: Everett, WA
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Originally Posted by nomorecatering View Post
Had a ride in my mates brand new B tripple the other day. 650 Hp and 2400 ft/lbs or torque coupled to I think, a 24 speed auto geabox, disc brakes on every axle. This is a state of the art truck. He grosses way over 90 tons. he reckons that his truck is way more pavement friendly that a traditional semi as he has lots more tyres to spread the load and that his hp would get him over any mountain in the USA, including the Eisenhower tunnel in Colorado.
Sure, he can go over, but he won't be going very fast - 6% grade (I forget for how many miles, but it's more than 5) - both ways. 11,000 feet saps power (40 ton trucks with 500 hp still crawl up the approaches), but the really fun part is going back down the other side. 40 ton trucks are limited to (IIRC) 17 mph going down to prevent runaway (and there are still several runaway truck ramps - and they nearly often show signs of having been recently used). I don't know what limit they'd put on a 90 ton truck going down but be assured it would be slow.
A couple years ago, a rock fall closed I-70 both ways through Glenwood Canon (west of the Eisenhower tunnels) while we were skiing in Breckenridge. While the road was closed west of us, we drove down to Denver for a 'day trip' - it was somewhat amazing since there were almost no big trucks - so no dodging the (normally numerous) slow moving trucks. What was normally a white knuckle drive was rather enjoyable.

Trans continental transport is better done with trains - far more fuel and cost efficient. The one area where trucks win is time - so it makes sense to move perishables by truck.
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Old 1st Jun 2018, 08:19
  #23 (permalink)  
 
Join Date: Nov 2003
Location: Surrey
Posts: 155
Was talking to the driver of a mobile crane a few years ago: one of the big multi-axle ones. His point was that they have more wheels & axles not only to spread the weight - which is a lot - but to increase the number of brakes. Additionally, you only go down a hill in the same gear that you went up it, regardless. So, 10mph up, 10mph down. No exceptions.
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Old 1st Jun 2018, 11:57
  #24 (permalink)  
 
Join Date: Feb 2006
Location: AMONGST BRIGALOW SUCKERS
Posts: 309
The triple road train trucks we operate, gross at 122.5 tonnes with 18 axles and 70 tyres. The prime mover (or tractor in USA speak) at that gross weight is very frightened of any grade or hill.. even with 620hp. Speeds in the order of 30km/h up a modest grade is not uncommon.
The use of these type of vehicles in places other than rural Australia would simply not work well.
I had a log hauler guy from Canada (where he routinely uses B double units) come for a run with me one day.. and I let him have a steer on the way back home unloaded. He enjoyed the experience of steering such a long vehicle, but stated that there is no way in hell such a unit would work in the USA or Canada for the reasons mentioned in previous posts. At one stage in the journey, we ran beside the railway line for over 200km from Charleville to Quilpie. He was astonished when I told him that although the line was maintained in working condition, not a single train had traversed that line in over 12 months. "I just don't get it" he said, as we passed dozens of vehicles similar to our own on the trip.

Australia does a lot of things well...but transport logistics and aviation regulation are not amongst them.
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