OV9

Dodge Ram Big Horn?

https://rover.ebay.com/rover/0/0/0?mpre ... 3597768416

Big horn.

Heh.

Interesting

Why does the RS6 not come with the 2500kg rating I wonder

https://usedcars.audi.co.uk/usedcar/aud ... 816017.htm#

Only 1 on the UK Audi Site with the factory towbar as well

NotoriousREV wrote: Wed Sep 25, 2019 5:33 pm Dodge Ram Big Horn?

https://rover.ebay.com/rover/0/0/0?mpre ... 3597768416

A Big Horn Cummins no less.

Get that Foz, Cummins Rams are CAF.

ZedLeg wrote: Wed Sep 25, 2019 6:01 pm

NotoriousREV wrote: Wed Sep 25, 2019 5:33 pm Dodge Ram Big Horn?

https://rover.ebay.com/rover/0/0/0?mpre ... 3597768416

A Big Horn Cummins no less.

Get that Foz, Cummins Rams are CAF.

M’colleague is 100% correct.

Sundayjumper wrote: Wed Sep 25, 2019 1:54 pm

V8Granite wrote: Wed Sep 25, 2019 1:36 pm For stability and being able to just sit at 60 all day long the Defender is great...

As long as it's a light trailer and there's absolutely no hills. I was driving this a couple of weeks ago, the trailer is basically an empty box with a desk in it, so not heavy at all, and on a slight incline (the A3 south out of Guildford if anyone knows it) it wouldn't top 40mph. With the full 3500kg it probably would have been down to first gear


IMG_0870.JPG

It was broken, I took a double axle trailer, my 500e and an FZR600 in the back and I could sit at 60mph. That was between Stanstead and Peterborough. The only issue is needing 4th to get to 60 but then 5th would hold that no problem. Probably a 5 ton total train weight.

Mine is tuned but only the fuel pin mod and extra boost, maybe 120hp on a really really good cold day.

Dave!

ZedLeg wrote: Wed Sep 25, 2019 6:01 pm

NotoriousREV wrote: Wed Sep 25, 2019 5:33 pm Dodge Ram Big Horn?

https://rover.ebay.com/rover/0/0/0?mpre ... 3597768416

A Big Horn Cummins no less.

Get that Foz, Cummins Rams are CAF.

Get the big Cummins, they are lurverly.

Dave!

V8Granite wrote: Wed Sep 25, 2019 7:02 pm

Sundayjumper wrote: Wed Sep 25, 2019 1:54 pm

V8Granite wrote: Wed Sep 25, 2019 1:36 pm For stability and being able to just sit at 60 all day long the Defender is great...

As long as it's a light trailer and there's absolutely no hills. I was driving this a couple of weeks ago, the trailer is basically an empty box with a desk in it, so not heavy at all, and on a slight incline (the A3 south out of Guildford if anyone knows it) it wouldn't top 40mph. With the full 3500kg it probably would have been down to first gear


IMG_0870.JPG

It was broken, I took a double axle trailer, my 500e and an FZR600 in the back and I could sit at 60mph. That was between Stanstead and Peterborough. The only issue is needing 4th to get to 60 but then 5th would hold that no problem. Probably a 5 ton total train weight.

Mine is tuned but only the fuel pin mod and extra boost, maybe 120hp on a really really good cold day.

Dave!

I was going to say I’ve found towing with the Defender a doddle but the maximum I’ve towed a few times by *cough* accident would be 2.5 tonnes including the trailer. Before the remap 15-25 mph would be awkward as there wasn’t enough torque in third so you had to wring our second but since mapping I can put it in third from 15 mph whilst towing and it’s happy. (6 speed box)

V8Granite wrote: Wed Sep 25, 2019 7:02 pm I took a double axle trailer, my 500e and an FZR600 in the back and I could sit at 60mph. That was between Stanstead and Peterborough. The only issue is needing 4th to get to 60 but then 5th would hold that no problem. Probably a 5 ton total train weight.

Mine is tuned but only the fuel pin mod and extra boost, maybe 120hp on a really really good cold day.

This has got me interested now. Because I'm bored and should really have been an engineer.

It should be some fairly simple maths to work out the maximum gradient that combo could maintain 60mph on.

The input data is:

120bhp
5 tonnes
60mph

I just need to look up the Cd of a Defender and chuck it all together. We'll assume this calculation suits the Defender's gearing, and 60mph happens to correspond to peak power

www.towcar.info

Quite a good site for matching, can add any modifications to the car power/torque etcs into it as well.

Sundayjumper wrote: Wed Sep 25, 2019 8:14 pm It should be some fairly simple maths to work out the maximum gradient that combo could maintain 60mph on.

Yes, I've spent over an hour and a half doing this

The formatting will be all to fcuk, but here we go....

------------------------------------------------------------------------------------------------------------------

Fixed Values
g 9.807 m/s²
ρ 1.225 kg/m3


Dave!'s Defender with a trailer, the 500E and a FZR600

Power 120 bhp = 89.484 kW
Mass 5 tonnes = 5000 kg
Velocity 60 mph = 26.8224 m/s
Drag Area 18.03 ft² = 1.67504109 m² from https://en.wikipedia.org/wiki/Automotive_aerodynamics
Cd 0.59 - from https://ecomodder.com/forum/showthread. ... -1924.html
Drivetrain loss 15 % (possibly a bit optimistic)


Calculations

A (frontal area) = 2.839052695 m²

General transmission loss = 13.4226 kW

Power on level ground = ½ ρ Cd A V3

= 19.79814326 kW

=> 56.26325674 kW available for going up hills


(incidentally, working backwards from here to calculate maximum speed on the flat you get 94mph - is that realistic ?)


Power to climb a gradient = m g v sin θ

θ = sin-1 ( P / (m g v))

θ = 2.451750267 degrees

equivalent to 1 in 23.35507208

------------------------------------------------------------------------------------------------------------------

Phew.

So to maintain 60mph, the maximum gradient is slightly steeper than 1 in 25. Which by a brilliant coincidence is the maximum gradient allowed on motorways except in "exceptional circumstances" where it can be 1 in 20.

There's obviously still a bunch of assumptions & omissions in there but it's close enough for now.

Dave!'s Defender & trailer could - possibly - do 60mph all day on the motorway. But it'd be absolutely flat out to achieve that most of the time.

I’d say towing at close to max payload is quite close to full load but it’s not flat out. The biggest issue I have with mine is that the inter cooler gets heat soak if I’m full throttle for long periods. I maybe have 10% left though if that. With a better intercooler I could maintain lower exhaust temps at the same time which would help a lot.

I’d say that the drivetrain loss is very optimistic, I think closer to 30% is more likely.

Mine has hit a GPS verifies 86mph but that’s on the governor in top, maybe I had an extra couple of mph with different gearing but not much.

So what can I tow with a 300ho Cummins then

Dave!

V8Granite wrote: Thu Sep 26, 2019 7:46 am I’d say that the drivetrain loss is very optimistic, I think closer to 30% is more likely.

Agreed. Even something like an AWD Impreza loses 25%.

So what can I tow with a 300ho Cummins then

Anything you want, Dave!

Foz wrote: Wed Sep 25, 2019 10:18 am So I want a new daily/tow car, I saw the current RS6 can be fitted with a factory deployable towbar, but its only rated to 2100kg, which is below the plated weight of my trailer - 2400kg so technically illegal.

You probably already know, but unless you're towing commercially, it's actual weight that matters legally, not plated weight.

scotta wrote: Wed Sep 25, 2019 11:00 am From the experience of towing the race shuttle with the XJR - Just dont.

one the way back from a race weekend we had a massive moment. Crosswind caught the trailer and the resultant weave took us out of the lane we were in without control back and forth between the lanes. Most scared in a car ive ever been. Honestly though we were going in to the central barriers. so much so i had pulled the seatbelt as tight as i could get it to go.

Stick with a 4x4 SUV/pickup.

Agreed. Absolutely fucking terrifying. Snake so violent it was picking up alternate rear wheels of the Jag. Still don't quite know exactly how it didn't end up in flaming upside-down death.

The biggest issue isn't the towing capacity, but the enormous distance between the rear axle and the tow bar, which gives any instability in the trailer massive leverage over the car.

I have only towed horse box and caravans but it was far easier in a 4x4 than in a car, for visibility and stability etc. My Grand Cherokee barely noticed a van on the back, it was only the 4.0 V6 with some piddling output (170 rings a bell) but it could have pulled a house.

Mine was LPG converted so not too horrific on juice.

I would imagine a LC would be pretty good, a lot of the horsey set round here have them pulling large boxes no problem at all.

Gavin wrote: Thu Sep 26, 2019 8:18 am I have only towed horse box and caravans but it was far easier in a 4x4 than in a car, for visibility and stability etc. My Grand Cherokee barely noticed a van on the back, it was only the 4.0 V6 with some piddling output (170 rings a bell) but it could have pulled a house.

Mine was LPG converted so not too horrific on juice.

I would imagine a LC would be pretty good, a lot of the horsey set round here have them pulling large boxes no problem at all.

*straight 6. 170bhp but 220lb/ft of torque.

V8Granite wrote: Thu Sep 26, 2019 7:46 am So what can I tow with a 300ho Cummins then

The 3500 Big Horn, in the US, 16 Tonnes

Not sure how that translates across to UK regs. Certainly to pull over 3500kg you run into masses of additional requirements about the trailer. Coupled brakes, larger hitch.