Flat towing a Rivian

stank65

Well-Known Member
First Name
Rich
Joined
Apr 1, 2019
Messages
48
Reaction score
20
Location
Coopersburg, PA
First Name
Rich
Vehicles
Tesla Model 3, Chevy Tahoe, GMC Acadia
No, the bar isn't going to fail ever unless it is overloading, or the towing vehicle gets in an accident. And the electric brakes fail all the time. That is why I went with a mechanical system which requires compression before the toad brake is applied.
If a quick release isn't properly seated and locked, bar will get destroyed if you put any compressive load on them. They should not fail even if put under full force of the vehicle, but again that is not what they are designed to have happened on a regular basis. There is a massive difference between a system designed to handle these loads regularly and safely vs a system that should be able to handle it in an emergency situation. A surge system would never reach the loads you are stating if it was working properly. The brakes are triggered before the spring/damper is fully compressed and it slams metal on metal. During that time, the only forward load on the RV is the spring/damper force.

AND if a propulsion system was put in place it makes your surge braking impossible.
 
Last edited:
OP
C

CappyJax

Well-Known Member
Joined
Dec 26, 2018
Messages
301
Reaction score
112
Vehicles
Subaru Forester
  • Thread starter
  • Thread Starter
  • #77
No, you are making shit up now.
 

stank65

Well-Known Member
First Name
Rich
Joined
Apr 1, 2019
Messages
48
Reaction score
20
Location
Coopersburg, PA
First Name
Rich
Vehicles
Tesla Model 3, Chevy Tahoe, GMC Acadia
No, you are making shit up now.
What am I making up?

There is no way that surge brakes are designed to take the anywhere near full force of the towed vehicle prior to applying the brake. That makes no sense.

If there was propulsion from the towed vehicle, it would compress the damper/spring in surge brakes and trigger the brakes.

Blue OX tow bars have a specific warning about driving distances greater than 1 mile without both of the arms fully locked out. The arms don't fully lock out unless you turn your vehicle in a certain way to get full extension on both arms. If a propulsion system was in place, you would have to drive until you think you are locked and then somehow engage the propulsion from the tow vehicle.
 

stank65

Well-Known Member
First Name
Rich
Joined
Apr 1, 2019
Messages
48
Reaction score
20
Location
Coopersburg, PA
First Name
Rich
Vehicles
Tesla Model 3, Chevy Tahoe, GMC Acadia
What am I making up?

There is no way that surge brakes are designed to take the anywhere near full force of the towed vehicle prior to applying the brake. That makes no sense.

If there was propulsion from the towed vehicle, it would compress the damper/spring in surge brakes and trigger the brakes.

Blue OX tow bars have a specific warning about driving distances greater than 1 mile without both of the arms fully locked out. The arms don't fully lock out unless you turn your vehicle in a certain way to get full extension on both arms. If a propulsion system was in place, you would have to drive until you think you are locked and then somehow engage the propulsion from the tow vehicle.
In theory you could have a tow bar that had a three way damper that could trigger brakes in compression, trigger acceleration in tension, and have a middle ground which would be neutral/coast, but that is a significantly more advanced (expensive) version of a surge brake. Even this setup could never give you propulsion, it would only get the towed vehicle to the point of coasting.
 

Hmp10

Well-Known Member
Joined
Mar 7, 2019
Messages
541
Reaction score
349
Location
Naples, FL
Vehicles
2015 Tesla Model S P90D; 2018 Honda Odyssey
Would someone please explain the point of all this.

It seems to me the only advantage of using flat towing to charge an EV is so that the battery will have juice to drive the vehicle when you arrive at a place that doesn’t have a charging station.

This notion of using a fully-charged EV that has been charged using flat towing to then help push the RV that is towing it in order to keep from “wasting energy” makes no sense. The fuel consumption of the RV was increased in the first place by having to overcome the drag that regeneration was creating. (The reason regenerative braking works is that force must be applied to the motors during regeneration. In braking, that energy comes from recovering the kinetic energy of the slowing of the vehicle. In power utilities, it comes from burning fossil fuels, heating water into steam, or capturing the force of running water. In flat towing, it comes from the engine output of the tow vehicle.)

First, you increase the RV’s fuel consumption to tow the EV while in regeneration mode. The EV battery fills. Then the EV battery drains while helping to push the RV. Then the RV fuel consumption increases again to replenish the battery charge that was drained while helping push the RV. (And remember that regenerative braking is considerably less than 100% efficient. It doesn’t recover all the energy that was used to accelerate the car in the first place.)

Really, what’s the point?
 
OP
C

CappyJax

Well-Known Member
Joined
Dec 26, 2018
Messages
301
Reaction score
112
Vehicles
Subaru Forester
  • Thread starter
  • Thread Starter
  • #81
Would someone please explain the point of all this.

It seems to me the only advantage of using flat towing to charge an EV is so that the battery will have juice to drive the vehicle when you arrive at a place that doesn’t have a charging station.

This notion of using a fully-charged EV that has been charged using flat towing to then help push the RV that is towing it in order to keep from “wasting energy” makes no sense. The fuel consumption of the RV was increased in the first place by having to overcome the drag that regeneration was creating. (The reason regenerative braking works is that force must be applied to the motors during regeneration. In braking, that energy comes from recovering the kinetic energy of the slowing of the vehicle. In power utilities, it comes from burning fossil fuels, heating water into steam, or capturing the force of running water. In flat towing, it comes from the engine output of the tow vehicle.)

First, you increase the RV’s fuel consumption to tow the EV while in regeneration mode. The EV battery fills. Then the EV battery drains while helping to push the RV. Then the RV fuel consumption increases again to replenish the battery charge that was drained while helping push the RV. (And remember that regenerative braking is considerably less than 100% efficient. It doesn’t recover all the energy that was used to accelerate the car in the first place.)

Really, what’s the point?
YOU DONT USE REGENERATIVE BRAKING ON THE TOAD WHEN THE RV ACCELERATOR IS APPLIED!!!!! How many times do we have to explain this simple principle. You only use it for slowing both vehicles. Please educate yourself and stop repeating this Bs.
 

Hmp10

Well-Known Member
Joined
Mar 7, 2019
Messages
541
Reaction score
349
Location
Naples, FL
Vehicles
2015 Tesla Model S P90D; 2018 Honda Odyssey
So you’ll arrive at your vacation spot with, what, 20 miles of range from regeneration on your battery after using the EV occasionally to push the RV? Great plan.

I’ve driven an EV for four years. You’re way overguessing how much charging you get from regen braking.
 

stank65

Well-Known Member
First Name
Rich
Joined
Apr 1, 2019
Messages
48
Reaction score
20
Location
Coopersburg, PA
First Name
Rich
Vehicles
Tesla Model 3, Chevy Tahoe, GMC Acadia
Would someone please explain the point of all this.

It seems to me the only advantage of using flat towing to charge an EV is so that the battery will have juice to drive the vehicle when you arrive at a place that doesn’t have a charging station.

This notion of using a fully-charged EV that has been charged using flat towing to then help push the RV that is towing it in order to keep from “wasting energy” makes no sense. The fuel consumption of the RV was increased in the first place by having to overcome the drag that regeneration was creating. (The reason regenerative braking works is that force must be applied to the motors during regeneration. In braking, that energy comes from recovering the kinetic energy of the slowing of the vehicle. In power utilities, it comes from burning fossil fuels, heating water into steam, or capturing the force of running water. In flat towing, it comes from the engine output of the tow vehicle.)

First, you increase the RV’s fuel consumption to tow the EV while in regeneration mode. The EV battery fills. Then the EV battery drains while helping to push the RV. Then the RV fuel consumption increases again to replenish the battery charge that was drained while helping push the RV. (And remember that regenerative braking is considerably less than 100% efficient. It doesn’t recover all the energy that was used to accelerate the car in the first place.)

Really, what’s the point?
The one scenario it could be helpful is the following. Note: I believe this is too small a window to be worth it.

If you use regen braking only while the RV is actually braking you are recovering energy that would have otherwise been transferred as heat in the brakes.

If you recover that braking energy via regen and not heat in friction brakes, AND you charge the battery to whatever you consider "full", the idea would be to use some of the power in the Rivian to assist in some form. The system would in theory run the Rivian battery down to a certain point assisting, and then stop assisting while the battery recharged back to "full". On an extended trip this would result in multiple cycles of assist and no assist while the battery would fluctuate between full and the lower limit for assisting.
 
OP
C

CappyJax

Well-Known Member
Joined
Dec 26, 2018
Messages
301
Reaction score
112
Vehicles
Subaru Forester
  • Thread starter
  • Thread Starter
  • #84
So you’ll arrive at your vacation spot with, what, 20 miles of range from regeneration on your battery after using the EV occasionally to push the RV? Great plan.

I’ve driven an EV for four years. You’re way overguessing how much charging you get from regen braking.
Not guessing at all. Is the RV and toad weigh 12,500kg, and they decelerate from 100kph, that will produce 1.3kWh. At 70% efficient regenerative braking, that is just about 900Wh of energy back in the batteries. Not spectacular if you are in the flat land on the highway. But let’s say you are in the mountains going down long grades. Going down a 5% grade for ten miles would produce over 5kWh per mile. A 10 mile run would give you 35kWh into the battles. . And that is just one downhill run. If you went for Vail to Denver, you would produce enough energy to fully charge most EV batteries. Also, you are saving a lot of wear and tear on the towing vehicles service brakes. It is free energy.

You simply don’t understand physics.
 

Hmp10

Well-Known Member
Joined
Mar 7, 2019
Messages
541
Reaction score
349
Location
Naples, FL
Vehicles
2015 Tesla Model S P90D; 2018 Honda Odyssey
Yes. A lot of mechanical complexity to handle push forces safely and a lot of electronic complexity to manage the charging scenario. All to a very marginal end.

I hope Rivian is spending its time on building a reliable vehicle instead of thinking about such fringe scenarios.
 
OP
C

CappyJax

Well-Known Member
Joined
Dec 26, 2018
Messages
301
Reaction score
112
Vehicles
Subaru Forester
  • Thread starter
  • Thread Starter
  • #86
Yes. A lot of mechanical complexity to handle push forces safely and a lot of electronic complexity to manage the charging scenario. All to a very marginal end.

I hope Rivian is spending its time on building a reliable vehicle instead of thinking about such fringe scenarios.

Only to people who don't understand physics.
 

stank65

Well-Known Member
First Name
Rich
Joined
Apr 1, 2019
Messages
48
Reaction score
20
Location
Coopersburg, PA
First Name
Rich
Vehicles
Tesla Model 3, Chevy Tahoe, GMC Acadia
Not guessing at all. Is the RV and toad weigh 12,500kg, and they decelerate from 100kph, that will produce 1.3kWh. At 70% efficient regenerative braking, that is just about 900Wh of energy back in the batteries. Not spectacular if you are in the flat land on the highway. But let’s say you are in the mountains going down long grades. Going down a 5% grade for ten miles would produce over 5kWh per mile. A 10 mile run would give you 35kWh into the battles. . And that is just one downhill run. If you went for Vail to Denver, you would produce enough energy to fully charge most EV batteries. Also, you are saving a lot of wear and tear on the towing vehicles service brakes. It is free energy.

You simply don’t understand physics.
I'd be interested to see your math on this and assumptions.

Seems like some of the assumptions have this number significantly higher than real life application.

What is your split between the energy absorbed by RV friction/exhaust brakes, Rivian friction brakes, and Revian regen? From the way you wrote this it seems you are counting the entire deceleration towards the Rivian Regen braking.
 
OP
C

CappyJax

Well-Known Member
Joined
Dec 26, 2018
Messages
301
Reaction score
112
Vehicles
Subaru Forester
  • Thread starter
  • Thread Starter
  • #89
I'd be interested to see your math on this and assumptions.

Seems like some of the assumptions have this number significantly higher than real life application.

What is your split between the energy absorbed by RV friction/exhaust brakes, Rivian friction brakes, and Revian regen? From the way you wrote this it seems you are counting the entire deceleration towards the Rivian Regen braking.
From the way you wrote this it seems you are counting the entire deceleration towards the Rivian Regen braking."

Yes, why wouldn't you?
 

stank65

Well-Known Member
First Name
Rich
Joined
Apr 1, 2019
Messages
48
Reaction score
20
Location
Coopersburg, PA
First Name
Rich
Vehicles
Tesla Model 3, Chevy Tahoe, GMC Acadia
From the way you wrote this it seems you are counting the entire deceleration towards the Rivian Regen braking."

Yes, why wouldn't you?
Because that isn’t right. In order for the Rivian regen breaks to be engaged, the RV brakes would have to be engaged also. It is also unlikely that the Rivian would break with only the Regen but I’ll just give you that one. At the absolute very best, the Rivian would account for a quarter to a third of the braking power on the downhill.
 
Top