Andreas,
Thanks for starting a new thread. You can see from the immediate response that a lot of us are interested.
As you already know, this will take money, time, and commitment from you because you are breaking trail for those of us who are already committed to the GMC design.
What we've found over the years is that the GMC was remarkable in its design of the drivetrain, suspension, streamlined exterior, efficient interior, driving experience with elevated cockpit, and living experience with the expanse of windows. It is a veritable symphony of successful compromises. You are addressing just one of these elements, the most expensive, planet unfriendly aspect. All of us current drivers want to know about an outcome that makes our coaches eco-friendly.
But many in the GMC community are old (I'm 78) and we look at passing our coach on to someone new. To imagine our coach with a modern drive train, appealing to a younger, ecologically aware constituency is to see a brilliant design have relevance into the future. That is a dream worth pursuing.
If you have the resources and the commitment, know that lots of people are behind you cheering you on.
Strength to the sword arm, brother.
Doug
Thanks for starting a new thread. You can see from the immediate response that a lot of us are interested.
As you already know, this will take money, time, and commitment from you because you are breaking trail for those of us who are already committed to the GMC design.
What we've found over the years is that the GMC was remarkable in its design of the drivetrain, suspension, streamlined exterior, efficient interior, driving experience with elevated cockpit, and living experience with the expanse of windows. It is a veritable symphony of successful compromises. You are addressing just one of these elements, the most expensive, planet unfriendly aspect. All of us current drivers want to know about an outcome that makes our coaches eco-friendly.
But many in the GMC community are old (I'm 78) and we look at passing our coach on to someone new. To imagine our coach with a modern drive train, appealing to a younger, ecologically aware constituency is to see a brilliant design have relevance into the future. That is a dream worth pursuing.
If you have the resources and the commitment, know that lots of people are behind you cheering you on.
Strength to the sword arm, brother.
Doug
A few years ago I considered doing a similar project. The difference was rather than using a single Tesla motor, I wanted to use six Lordstown hub motors, unfortunately the Lordstown Motors company went belly up before going into full production.
Some of the other features I considered were...
- Smoothing all surfaces of the body. No roof racks, no roof mounted A/C's, remove the side mirrors and use cameras, flush mounted glass and possibly fabricating tubular bumpers.
- Six wheel air bag suspension so the entire coach could be lowered at highway speeds, similar to classic Citroen's.
- The tubular bumpers would be used as air tanks for the suspension as well as for inflating tires, air tools and pneumatic leveling jacks while parked.
- A pneumatic retractable front air dam with distance sensors to ensure it was not lowered too far and the ability to automatically retract to clear road hazards.
- I also wanted to stretch the coach's overall length to incorporate a compact garage space for my motorcycle. The rear screwed on panel would be replaced with hinged barn-doors with two mounted spare tires.
- An extended chassis would be needed so I imagined making it from a little taller channel which would help with the additional weight of the batteries.
- Since the drivetrain would consist of hub motors, the engine compartment would be empty. This would allow space for a heat-pump, a generator and small fuel tank, onboard computer(s) and other bulky accessories.
- The entire length of the smooth roof would be covered with curved solar panels on 1 inch stand-offs acting like a Land-Rover safari-top to reduce solar heat absorption.
- Any large, non-glass, panel on the body sides would be covered with flexible, adhesive solar panels. Between the roof and sides I estimated 320 square feet of solar panels.
- In addition to charging the batteries at commercial charging stations it would have the ability to charge from the solar panels, household 220v and (worst case) 110v power and an onboard generator.
The idea of an electric GMC coach quickly faded as Lordstown Motors dissolved as well as the occasional news reports of electric vehicles occasionally spontaneously combusting.
I found that my GMC Glenbrook would coast downhill from Siskiyou Summit in Oregon, at 65 mph when the transmission is in neutral. That is a 6% grade. The force pushing the coach at that speed is about 600 pounds (approximately 10,500 * .06). 600 pounds times 95 feet per second =
104 Horsepower. If the drag varies by the square of the speed, it would take 89 horsepower to travel at 60 mph. If a Tesla model Y battery pack is used, weighing about the same as a GMC drivetrain, I get this result:
Battery capacity; 75 KWH divided by 746 W/HP = 100.5 Horsepower Hours
You might be able to go 65 miles in one hour (at 65mph flat ground), with a 100% charge and none remaining. But the Tesla Model Y motor would probably overheat.
With 3 Model Y battery packs, (225 KWH) maybe triple the distance or about 200 miles. But the weight of 3 battery packs is around 3000 lbs. With a 150 KW Tesla charger, it would take a few hours to charge, if there was a BMS system that can work with the hardware.
104 Horsepower. If the drag varies by the square of the speed, it would take 89 horsepower to travel at 60 mph. If a Tesla model Y battery pack is used, weighing about the same as a GMC drivetrain, I get this result:
Battery capacity; 75 KWH divided by 746 W/HP = 100.5 Horsepower Hours
You might be able to go 65 miles in one hour (at 65mph flat ground), with a 100% charge and none remaining. But the Tesla Model Y motor would probably overheat.
With 3 Model Y battery packs, (225 KWH) maybe triple the distance or about 200 miles. But the weight of 3 battery packs is around 3000 lbs. With a 150 KW Tesla charger, it would take a few hours to charge, if there was a BMS system that can work with the hardware.
Page 4 of this document shows a graph of speed vs HP and torque to push a GMC motorhome down the road. It shows 50hp at 55mph. I assuming a level road and no wind.
Some other good info in the paper as well.
I do not know where the Authors pf the paper got this info came from.
Some other good info in the paper as well.
I do not know where the Authors pf the paper got this info came from.
Nice! Too bad they didn't include their assumptions about drag for the HP/torque chart.Page 4 of this document shows a graph of speed vs HP and torque to push a GMC motorhome down the road. It shows 50hp at 55mph. I assuming a level road and no wind.
Some other good info in the paper as well.
I do not know where the Authors pf the paper got this info came from.
