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 > Your search for posts made by 'RoyJ' found 78 matches.

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  Subject Author Date Posted Forum
RE: TFL Truck tests Ford Raptor vs Ram TRX towing on I-70

Regardless of weight, performance testing on these "super trucks" may be a moot point, as all can pull even 10k lbs at speed limit the entire way. We're talking 700 hp here for 11k - 16k GVW. That's double to triple the hp-weight ratio of regular trucks at max GVW.
RoyJ 01/19/21 04:10pm Tow Vehicles
RE: Towing capacity vs max cargo weight rating

There's one tire size (other than 19.5s) that can get us close to the DRW axle capacity: https://www.tirerack.com/tires/tires.jsp?tireMake=Continental&tireModel=VanContact+A%2FS&partnum=865R6VCAS&vehicleSearch=false&fromCompare1=yes 4300 lbs / tire, or 8600 lbs GAWR. Factor in the SRW bed is a bit lighter, and we have one less set of tires / wheels, that probably puts us within 500 lbs of a dually.
RoyJ 01/19/21 04:04pm Tow Vehicles
RE: Towing capacity vs max cargo weight rating

Hello, OP here. I guess I was concerned with the legalities of things first and foremost. We did use our truck to pull a 12,500 lbs horse trailer around the West for months, camping with our two horses full-time (it weighed about 2800 lbs on the hitch). The truck _appeared_ (!) perfectly capable to tow this trailer and stop it - I am not the kind to fly about with a trailer with livestock attached in the back anyway, my self-imposed limit is 65mph when I tow. Now, with that said, we bought the truck brand new in 2016 (F-250 4x4 diesel, crew cab, short bed) and it squatted something awful when we put the trailer on. I had to go the next day and get a set of "super springs" installed on the back, to level the truck under load. We traded in a 2006 GMC 2500 diesel 4x4 crew cab to get the new Ford and interestingly enough, the 10 years older GMC did not squat much with the same trailer (it too appeared perfectly capable to tow the trailer) - this tells me that personal anecdotes mean little in these discussions as sometimes all they are is "ignorance is bliss" kind of approach :) Thanks! :) That's why legality and safety can be 2 separate things! Every State and Province have their own weight laws. I live in a rare place (BC) that does enforce GVW. However, unless you're visibly overloaded, you'd never get pulled into a commercial scale. So ironically, an older truck with stiffer springs is less likely to get questioned than a newer sagging one. But safety it's a lot more than just springs. My old 2500's chassis is worn out, and components are not that stiff by modern standards. With 5000 lbs in the bed, the steering is so poor it truly feels like a boat. A modern F250 / 2500, may technically have less payload, but will handle MUCH better with a set of helper springs.
RoyJ 01/18/21 11:25am Tow Vehicles
RE: Towing capacity vs max cargo weight rating

Well from 1994 to 2002 Dodge/Ram didn’t offer a SRW 3500 the 2500 with camper package and optional 265/85-16E tires gave it plenty of capacity NONE of which I was reflected in the VIN sticker front axle 5,200#, rear axle 6,084# and GVWR 8,800#. The camper package included the same rear springs as the 3500 DRW, tires rated at 3,415# ea. The standard tires were 245/75-16E rated at 3,042# ea. My guess for the 8800 GVW is lack of tire selection in the 90's. I still have my old camper pkg V10 2500, and can verify the springs will indeed hold up well over GVW without sag. I've had over 5400 lbs of sand with the rear maybe an inch lower than the front! But, mine came with 245/75R16 tires. So Dodge probably specced the GVW based on the smallest tire. If 20" tires were available with 4000 lbs capacity, they could've easily made it 11k GVW "3500 SRW".
RoyJ 01/18/21 01:18am Tow Vehicles
RE: Towing capacity vs max cargo weight rating

The entire insurance industry is based on "What if's" No, it's based on proving, beyond reasonable doubt, that the accused reason is true cause of the accident. Reasonable doubt are you kidding? Insurance companies will seetlle all kinds of claims if they think its prudent. There is no guilt with liability. Guilt is associated with criminal cases. Liability can be very subjective. Never the less if the insurance company figures it's cheaper to settle vs. fighting it in court with a lawyer. They won't hesitate to settle, even if they believe they were not truly liable Your rates are based on what if this RV is totaled? Who is the bigger risk the guy with a clean driving record or the guy with 3 DUI's in 3 years? What are the chances of the 50 year old male crashing vs. an 18 year old teenager crashing. What car is more likely to have an accident a Corvette or a Camry? All these if's are what the insurance company ultimately pays for and also what we pay for. I'm not asking you how insurance rates are calculated. Let's back up a bit: an overloaded 2500 towing toyhauler causes an accident (your scenario). If insurance settles, like you mentioned, then the driver doesn't have a problem does he? His insurance goes up, but it would go up regardless of "overloading". What I'm saying: when insurance coverage is denied (typical scare tactic), this then goes to civil / criminal court. Now we're getting serious, this is where you need to prove, beyond reasonable doubt, the toy hauler / 2500 combo caused the accident. If I'm the expert witness engineer, first thing I'd check is: does the 3500 SRW truck have the same rear brake caliper, rotor, and pads. If so, then braking is not an issue (provided toy hauler is within 3500 SRW limit). Trailer brakes remain constant. So obviously braking power is not the cause of the accident.
RoyJ 01/14/21 09:44pm Tow Vehicles
RE: Towing capacity vs max cargo weight rating

The entire insurance industry is based on "What if's" No, it's based on proving, beyond reasonable doubt, that the accused reason is true cause of the accident.
RoyJ 01/14/21 04:24pm Tow Vehicles
RE: 2021 Cummins 1075 lbft peak torque at 1356 rpm

It’s not all about speed up a hill (especially a hill that very few on this forum ever drive). RAM needs to change transmission to improve driving dynamics and efficiency. And I’m not sure there is a formula or chart for you to create that will show that. We know from the Cummins bsfc map peak efficiency is a small window from 1500 - 2000 rpm, and roughly 50% to 75% of peak torque output. What I'll try is running the model with the engine restricted to 75% torque (say, 800 lb-ft), and forced upshift at 2100 rpm. I bet that's where the 10 spd shines. To be fair, 43,500 lbs would be a bit much. I'll try 26,000 lbs, 8k truck and 18k toy hauler.
RoyJ 01/14/21 04:21pm Tow Vehicles
RE: 2021 Cummins 1075 lbft peak torque at 1356 rpm

Comparing the acceleration or even hill climbing traits of a 3.31 10 speed to that of a 4.10 6 speed really needs to be shown in light of comparing the fuel economy in high gear between the two set ups. In order to obtain similar cruising fuel economy the two transmissions would have to be set up with similar final drive ratios .... with final drives equal the advantage of the 10 speed would be revealed comparing acceleration and heavy pulling performance. Agreed. I was just showing the 6 spd can be tuned for all out performance. Since the Aisin and 10 speed have similar top gear ratios, by using 4.10 the Aisin would give up a lot on empty cruising mpg. At the end of the day, there's no denying more gears ARE better, all else being equal.
RoyJ 01/14/21 04:18pm Tow Vehicles
RE: Towing capacity vs max cargo weight rating

Exactly and you don't have to be a CSI detective to see that the 2500 SRW truck is overloaded pulling that 42'toy hauler, based on its GVW figures. Would not take much to find towing parameters and ratings for the combo involved. It's really not that complicated. Is a Kenworth hauling a Cat D11 on a heavy-haul lowbed trailer "overloaded"? Compared to the standard 80k GVW reefer? What's a towing parameter of a Kenworth to begin with? Why is he legal on the road once all overweight permits are bought? What if he rear-ended a family in a minivan? How's a 20k lbs tractor towing 250k lbs trailer safer than an 8k lbs 2500 towing an 18k toy hauler? There are literally millions of vehicles on the road beyond typical rated use. If we go with "what ifs", then we better all stick with OEM Corollas driven at 50 mph down the freeway.
RoyJ 01/13/21 11:49pm Tow Vehicles
RE: Towing capacity vs max cargo weight rating

Who says debris gets spread around in every RV wreck? All one has to do is rear end someone at a stop sign/light and cause injury. Only thing messed up is the front of the truck/SUV. The trailer would still be 100% intact. In this case, regardless of "over-loading", the person would be 100% at fault anyway. For them to further blame it on trailer weight, they'd have to prove it. It'll likely involve hiring an engineer as an expert witness. Why would they when it takes no effort to prove the driver is already 100% at fault? Technically everything non-OEM on your truck can be blamed, I don't understand why we always emphasize on trailer weight. When's the last time any of us checked all brake friction materials exceeded OEM spec? What about over-sized tires? Lift kit? Tires with lower friction than OEM? Inertia brake controller at correct angle? Corrosion on electric brake wiring? You name it, with enough money behind a lawsuit, they can lay the blame on!
RoyJ 01/13/21 11:42pm Tow Vehicles
RE: 2021 Cummins 1075 lbft peak torque at 1356 rpm

Here's distance vs time for both trucks: https://i.imgur.com/XzfFDkX.jpg Conclusion - if you have a 10 spd racing against your buddy with a 6 speed, time the race to 70 sec, you'll be at 1143m, with him at 1102m. Then say "told ya should've waited, beat your by 120 feet" If you have the 6 spd, race him to 190 sec, where you pass him and say "told ya a 10 spd is waste of money" ;)
RoyJ 01/13/21 02:25pm Tow Vehicles
RE: 2021 Cummins 1075 lbft peak torque at 1356 rpm

Here's a fun question, what if we "sand-bagged" the PSD with an Aisin 6 speed? The be fair, I used a 4.10 rear end vs the 3.31 on the 10 speed. Surprise the overall 1st gear ratio becomes nearly identical, so performance is strictly down to gear gap: https://i.imgur.com/0KRgbVJ.jpg The thrust tells us something really interesting: https://i.imgur.com/aTtnKO6.jpg The Aisin is only able to hit 3rd gear, but the final thrust (and therefore overall gear ratio) is almost an exact match to 4th on the 10 speed. This means given enough time (big enough hill), the Aisin truck will reach the same speed. Sure enough, my raw data says @ 200 seconds, the Aisin truck hits 44.7 mph, @ 2752 rpm and 475 hp. That's 1 mph faster. At 190 seconds into the race, the 10 speed has covered 3493 meters, and the Aisin 3494. So the Aisin passed the 10 spd by 3 feet at 3 min 10 sec. It was quite a bit behind at the start.
RoyJ 01/13/21 02:11pm Tow Vehicles
RE: 2021 Cummins 1075 lbft peak torque at 1356 rpm

Here's the speed vs time output. My gear shifts are 200ms, during which I assigned an arbitrary 50hp (difficult to estimate engine output during clutch pack switch-over): https://i.imgur.com/PthBF5Y.jpg So @ 60s, our rig reaches 43.4 mph. At 120s, 43.8 mph, which is pretty max our V-max climbing this grade. This happens at 2881rpm in 4th, hp is 464. Here we can see the gross thrust, before aero, tire, and gravity drag vs speed. Think of this as "drawbar pull" on a tractor: https://i.imgur.com/nmdotp8.jpg 17.67 kN, or 3971 lbs. Also in 4th of course.
RoyJ 01/13/21 01:46pm Tow Vehicles
RE: 2021 Cummins 1075 lbft peak torque at 1356 rpm

^^^ I figure a Ram towing a typical 20,000 lb toy hauler should get around 9 mpg at 62 mph. If you use the BSFC map that we have and figure the Cummins will be running in the 205 g/kwhr area of the bsfc map we can come up with the kw required to tow a 20k trailer at 62 mph. 9 miles per gallon is 22182 grams of fuel per hour. 22182/205 = 108 kw or 145 HP. From there you should be able to come up with what you think are reasonable numbers for surface area, rolling resistance and coefficient of drag. (Keep in mind that the calculated power requirement is at the crankshaft so rear wheel hp would only be about 123 to 125 hp.) I'm trying the Powerstroke with 10 spd first, as it's a real combo and we can calibrate against real life performance. First the curve fitting based on your numbers, a 5th order poly provides near exact fit, with R^2 of 0.9998: https://i.imgur.com/66sAh53.jpg I re-calculated hp using the equation in the last column, and numbers are near perfect to the input. For the model, I used a mass of 43,500 lbs, full GVW of an F450. Cross section area of 75 sq ft, based on J2807's max for travel trailers. I guessed a Cd of 0.80. Tire diameter based on 245/75R17, and tire coefficient of 0.015. I'm starting out full throttle on 7% grade, as a "torture test". The model uses a column for each gear, each row is 0.1s time step. Based on initial launch rpm (2000), it uses the hp curve to calculate final net thrust: gross thrust minus air drag, tire drag, and gravity. Net thrust calculates instant acceleration, which gets ups the new starting speed for the next 0.1s time step: https://i.imgur.com/tqTHjN5.jpg
RoyJ 01/13/21 01:38pm Tow Vehicles
RE: 2021 Cummins 1075 lbft peak torque at 1356 rpm

Such a torque curve would generate a power curve like this: https://i.imgur.com/MH9s56Ql.png I bet you're not far off. Here's the power curve from the 419hp marine QSB 6.7: https://i.imgur.com/81jIAFz.jpg If that's true, no calculations needed - even with the Aisin, you'd just have a constant 420 hp at any reasonable towing speed. I once wrote a HP-acceleration model in excel when bored working at Daimler. It takes a dyno curve, fitted with an equation, and then uses a finite element model concept to chop up time into 0.1s segments. I've checked it against magazine 1/4 mile times and it's accurate within 5%. But for trailers, the tough part is finding coefficient of drag and cross section area. At 37k lbs GVW it may not matter much, but with light trailers and 70 mph speeds it would. Maybe I'll dust it off for fun. I can try parameters like initial speed = 65 mph, grade 7%, GVW 30k lbs, and see how long / how much distance it takes for the rig to slow down to a constant speed.
RoyJ 01/12/21 11:37pm Tow Vehicles
RE: 2021 Cummins 1075 lbft peak torque at 1356 rpm

Isn't time to put this thread out to pasture? Welcome to the internet, folks! We all have our kicks. For some it's finding the most scenic route, and discussing counter-top options of the latest 5th wheel. For some it's playing Cummins / Ram engineer wannabe when it's cold and rainy :B
RoyJ 01/12/21 02:14pm Tow Vehicles
RE: 2021 Cummins 1075 lbft peak torque at 1356 rpm

Good grief... Yup, lot's of confusion. I'm not sure what happened. Immediately after posting my torque curve reflecting 430 peak HP I checked Ram's website and saw they are advertising 420 HP, so, I changed my torque graph within about an hour. I don't know if Roy got a copy of my graph before I changed it or if he was thinking 430 HP from other sources. You can find claims anywhere from 400 to 430 HP for the 2021 Cummins. Edit: I'm almost certain that even Ram's website was initially showing 430 HP for the HO engine but they currently are advertising 420 HP. Let's me try re-shaping the equation for 420 hp. I too was confused, some sites quoted 430 hp, some 420. I don't believe the official specs are on Ram's site yet, but I do see 420 stated on Cummins' site: https://www.cummins.com/news/releases/2020/12/04/2021-ram-heavy-duty-legendary-pickup-engine-better-ever What we really need is the official tq / hp curve. If the curve has flat hp plateau like we see on the marine QSB, then a 6 spd vs 10 spd would make very little difference in flat out performance. In fact, tonight I'll try it for fun with the QSB curve. Let's call it a lightly modded / chipped truck - i.e. programmer in "tow" setting. I bet it'll make absolutely 0 difference (engine hovers @ constant hp during an upshift)
RoyJ 01/12/21 02:12pm Tow Vehicles
RE: SRW Tires

^Its actually the 17” tires that are low rated, not the wheels. At least from previous research back when I had 17s under the truck. But same difference. 17s are no good for heavy hauling anymore. Make nice off road wheel size though. I wonder why all 17 tires appear to be frozen at 3195 lbs weight limit, regardless of how big they are. Starting at 245/75r17, all except the 37" are capped at 3195. Above a certain size, even the E rated are capped at 65 psi. 16s, 18s and 20s don't have this issue.
RoyJ 01/08/21 05:28pm Tow Vehicles
RE: 2021 Cummins 1075 lbft peak torque at 1356 rpm

Towing 63 mph I’m at 1750 in 5th and putting out 600 Nm (110 Kw) or 1432 in 6th putting out 733 Nm (110 Kw) and getting the 9 mpg. 70 mph empty we are both at 1594 in 6th getting 18 mpg putting out 333 Nm. (55 Kw) Pulling a 7% grade I’m able to do 45 mph at 2170 rpm putting out 1277 Nm (290 Kw) and according to the bsfc map I should be using 205 g/kwhr which would put me at 2.44 mpg and again you’re not going to do any better. We're probably splitting hairs, as this is all theoretical. Using 388 hp as the target, 10 spd: https://i.imgur.com/amVKYAH.jpg 6 spd: https://i.imgur.com/0Ay8Mzg.jpg Both are pretty much 100% throttle. What's more interesting is if the grade gets steeper, the 10 spd can drop TWO gears, down to 4th, and still maintain 45 mph. It might lose 1 mph in order to bring the rpm from 2892 down to 2800, where it develops the full 430 hp. But the Aisin would be forced to 2nd and slow down to 38.6 mph
RoyJ 01/08/21 03:59pm Tow Vehicles
RE: 2021 Cummins 1075 lbft peak torque at 1356 rpm

I missed a scenario. I think towing into the wind at 55 mph would take us about 150 Kw. I’d be running in 5th @ 1528 rpm so 937 Nm. That should put me about 200 g/kwhr and 5.9 mpg. You’d run in 8th @ 1687 and be putting out 849 Nm. You should be close to the middle of the sweet spot say 192 g/kwhr ..... 6.1 mpg! I used a target of 201 hp and picked the gear that falls into the dark blue land on the BSFC. 1st up, the 10 speed: https://i.imgur.com/MqQe9xg.jpg Now the 6 speed Aisin: https://i.imgur.com/SM9CcRq.jpg Here's the fun part, with the 10 spd: 1694rpm @ 623 lbft (845 Nm) falls right in the middle of the dark blue region. With the 6 spd, 1535rpm @ 691 lbft (936 Nm) just falls outside by the old map. So with the 2019 engine, we theoretically lose about 5% fuel efficiency. But I wonder if coolant temp / egt is better at the 10 spd's higher rpm.
RoyJ 01/08/21 03:42pm Tow Vehicles
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