Mounting Generator in Spare Tire Bay?

[Nova Eona]

Hey all, so I've got an Onan RV QG 3600 LP that I'm trying to figure out where to mount.  The condenser bay is the easy option, but I've been considering the feasibility and wisdom of mounting it in the spare tire bay behind the front bumper on my 4104.  I know the Technomadia folks did it with a 2500, but my 3600 is a half-inch too tall in default form to just slide in.  So that's got me wondering; what if I put a cutout in the floor of the spare tire compartment which the generator could slide up and into(with a steel framework built around it for support)?  I can't imagine the sheet metal there is structurally significant, and it would leave a lot of nice usable space available in my condenser bay.

Has anyone ever done similar, or have any advice on the matter?


P.S. Can't wait for warmer weather.  Being a Bus Nut in a New England winter is tough.

[richard5933]

I can't say definitively if the sheet metal is structural or not, but after my experience getting hit head-on in a GM 4106 by a Honda and walking away would make me hesitant to remove any metal from up front without carefully thinking things through.

We got hit somewhat offset towards the driver's side, and after impact the Honda was deflected towards the outer edge of the bus rather than continuing straight back. My thought at the time was that the strength gained by all the boxing in and around the spare tire compartment helped to deflect the impact outwards. If you look at the photo, you'll see that the vertical side wall of the spare tire compartment held basically intact, and the car was pushed into the compartment under the driver. Nearly all the damage was taken outwards of the spare tire compartment.

Not sure how much the floor of the spare tire compartment played into all this, or if we were just lucky in where we got hit, but it would make me think twice about removing anything without reinforcing things well.

I know that these are two different models we're talking about, but I believe the basic construction is pretty similar in the nose.

Another concern would be if the tow hooks ever are used. The floor of the spare tire compartment would be important in keeping the two hook from pulling towards the center. If the floor is removed, something else should be added to provide stability between the hooks.

Just my two cents' worth.

[Nova Eona]

I should clarify that my plan would be not to remove the entire floor, but just a rectangular section after which I would reinforce the edges.  The floor as-is is 44"x34", wheras the generator is only 31"x20".  The only way I would feel comfortable with this would be by installing a steel frame around the generator's footprint extending to the edge of the compartment, which if done right would actually leave the compartment more structurally sound than if it just had a loose tire in it.

[richard5933]

That's all I was saying - the structure of the floor needs to be maintained, in my opinion. Assuming that you tie the reinforcement into the structure and not just the sheet metal, I'm sure you can configure something that would be adequate to maintain the integrity.

My point was to encourage you to really think this though, since there's not much between you and the car in front of you.

[sledhead]

if you are good at fabrication I think it would work and might even add some strength to the front end as most sticks and staples that are of a higher quality do the same thing all the time some with power or air slides so you can change the oil easier on the genny

dave

[luvrbus]

There nothing under the floor on GMC for structure support even the 2  tow hooks are light weight with 3/8th bolts holding each one, take the floor out and look there is not much metal except on the sides,the floor I recall is only 1/8th thick it is not going to help much structurally it is just a floor for a tire with 1/8 or 3/16th metal for a frame

[Jim Blackwood]

On today's cars there may not be any metal in the body that is as thick as that 1/8" floor. Most of it is 1/4 as thick.

Jim

[chessie4905]

The weight of one on line is 172 lbs. It is enclosed, so without an enclosure, probably weighs about 160. I think a tire and rim weigh close to that. With proper reinforcement, should work fine. Cooling it, dunno. The heat coming up to the driver's area in the summer may need some thought on insulation.

[peterbylt]

Richard,

Just curious, did you have a spare tire in there at the time?
Wondering if the spare tire is part of the engineering in crash protection?

Peter

[richard5933]

Richard,

Just curious, did you have a spare tire in there at the time?
Wondering if the spare tire is part of the engineering in crash protection?

Peter

Very much so. It fit in there with a shoe horn. It had virtually no space in front or behind it, and maybe an inch on each side. Top to bottom there may have been an inch or so of space remaining.

The force of the impact was enough to shove the front-left wheel back and into the bulkhead behind it. The wheel hit the bulkhead with enough force to dent a metal toolbox stored in the compartment rearward of the bulkhead. Yet, the area around the spare tire was left virtually the same shape and size as before the collision.

Looking down the side of the bus after the impact, it was obvious that the force had been absorbed all the way down the length of the bus. The siding was rippled nose to tail, indicating that the unibody construction did exactly what it was intended to do.

I cannot say what would have happened if the Honda had hit us a few inches further towards the midline of the bus. My gut tells me that the Honda would largely have been driven down and under the bus, similar to how it traveled under the floor of the driver's area. I also cannot say what the result would have been if the Honda had been a Ford F150. I'm sure the result would have been worse for us, probably much more so. Even more reason to make sure the integrity of the bus is maintained.

This whole thing reminds me of the competition in junior high shop class where we were given a sheet of 18" x 24" heavy-weight card stock. The only other item allowed was white glue. The assignment was to create a structure to span a gap of a certain size, and our success would be measured by how much weight the structure would hold. Amazing how much weight those pieces of card stock ended up supporting by creating complex supporting members from it.

Yes, the sheet metal in the floor of the spare tire compartment may only be 1/8" thick aluminum. But it's not doing the work itself. There is an intricate assembly of supporting members, rivets, sheet metal, and more. The end result is a unified structure that is much stronger than any one component alone would be, just like the card stock was in junior high.

Is the floor of the spare tire compartment a critical component to the structure which makes up the front of a GM bus? Don't know. Way above my pay grade. But, like I said earlier, I would hesitate to remove it without careful analysis and much thought.

I'm not saying don't move forward with this project. Not at all. I'm merely saying to do so with careful planning for a worst-case scenario. I'm certain that with proper reinforcement this could be done, but I wouldn't even pretend to offer an opinion on the best way to do that.

Sorry for being so long-winded here. Don't want to be preachy or tell anyone what to do with his bus. I'm just trying to express my thought process on this, for whatever it's worth.

[luvrbus]

There nothing under that plate for structural look how the bumper is installed on a 4106 it has a 1/2 steel like bracket attached to the bumper on each side with a bolt in the middle of the bumper to adsorb and strengthen the bumper in the middle if ever hit in the middle of the bumper.Removing the floor and adding a generator with a few braces would probably help a GM.I have had to replace rusted metal on a GM tire compartment before it's thin except the 2 outer braces where the bumper attaches to the bus

[buswarrior]

There is no "crash protection" intended in the design of these older buses.

You get what you got, a degree of keeping costs down in small contacts and that's it.

That coach has just as little weight of materials in it, as it needed to maintain its shape and make it down the road.

Richard's good fortune was in the honda striking the same bits that hold the coach together.

Build your conversion to support the loads you place in it, you aren't going to accomplish anything useful in trying to do "crash protection"

Seen a modern MCI strike a wall?

https://m.youtube.com/watch?v=EFlGHxV5WsY

Don't expect anything older to do any better.

Choose a god, consider your sins, get down the road?

Happy coaching!
Buswarrior

[luvrbus]

There is no "crash protection" intended in the design of these older buses.

You get what you got, a degree of keeping costs down in small contacts and that's it.

That coach has just as little weight of materials in it, as it needed to maintain its shape and make it down the road.

Richard's good fortune was in the honda striking the same bits that hold the coach together.

Build your conversion to support the loads you place in it, you aren't going to accomplish anything useful in trying to do "crash protection"

Seen a modern MCI strike a wall?

https://m.youtube.com/watch?v=EFlGHxV5WsY

Don't expect anything older to do any better.

Choose a god, consider your sins, get down the road?

Happy coaching!
Buswarrior

That is it a nut shell ,GM buses are bad about dropping at the stairways and door because they have nothing structural in that area
 

[richard5933]

That is it a nut shell ,GM buses are bad about dropping at the stairways and door because they have nothing structural in that area

I did see this happen to ours. After the collision we veered off into the ditch on the other side of the road (steering and brakes were taken out by Honda). Fortunately, there was a driveway going across the ditch, which kept us from rolling. As the nose of the bus pushed into the berm at the edge of the driveway, it pulled the nose down about 1-1/2". This is when the windshields fell out, and it did put a crease across the bus running from the stairwell all the way across the bus to the driver's window.

In the end, I can't say what exactly kept us alive through the collision. You guys are probably correct that a generator can safely be put in the front bay. But, I hope you'll understand my reasons for being concerned about structural integrity. Especially if what you're saying about the minimal structure up there to begin with.