Has anybody seen this bus before:
http://blog.hemmings.com/index.php/2012/02/08/more-chris-bohman-creations-through-his-advertisements/ (http://blog.hemmings.com/index.php/2012/02/08/more-chris-bohman-creations-through-his-advertisements/)
Even though it is a nice looking job on the 4104 it seems a big waste of time when there are so many nice upper deck buses available?
It appears he grafted an auto hardtop convertible section on, these things have no structural strength at all.
My worry would be what he did to the top structure to keep the original strength of the monocoque design, one of the main advantages of a bus in the first place!
Who cares about structure, it just looks cool. Thanks for posting it, nice to see someone followed their dream...
Quote from: gus on February 08, 2012, 04:20:04 PM
Even though it is a nice looking job on the 4104 it seems a big waste of time when there are so many nice upper deck buses available?
It appears he grafted an auto hardtop convertible section on, these things have no structural strength at all.
My worry would be what he did to the top structure to keep the original strength of the monocoque design, one of the main advantages of a bus in the first place!
But that was what the man wanted, and it seems he had more $ than sense.
Still way cool!
;D BK ;D
Hard to believe Gus would even mention structural changes if you ever saw the changes to his 4107 Sundance did
Looks like a 1951 Ford Victoria roof. Some where from 51 to 54 I think.
Quote from: kaptar on February 09, 2012, 10:20:08 AM
Looks like a 1951 Ford Victoria roof. Some where from 51 to 54 I think.
Somebody posted at the Hemmings blog that the car roof could have been a 54 Mercury Sun Valley. The glass part on top matches a Nerc, but the side windows look different to me.
Fraser, maybe somebody could put a corvair on top of their bus. ;D
A classic piece, kinda late to tell them that it won't work now! Some people quack me up!
I haven't found any structural changes in my 4107. A couple of holes in the baggage compartment floor but nothing significant. I don't think end caps have much to do with structure.
There was some pretty weird stuff done with the woodwork though!!
Am I missing something?
Structure does matter, very much so!!
On the other hand these old round top GMs are so overbuilt it would take a lot of holes to make it as weak as newer square ones!!
My MCIvair
You guys wanting to stick car roofs on buses have got no ambition - here's the solution:
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2F18.mm.g-media.com%2F906327.jpg&hash=0df4e9c7bc458e3b6e0a94b9d63df4acabf9f58d)
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2F18.mm.g-media.com%2F688070.jpg&hash=b8d9c3efa7bfb150b9ba02e8aa41bc50b730b61e)
For those who don't recognise it - no, it's not Photoshop - it's a real vehicle which appeared in one of the Harry Potter films
Jeremy
Quote from: gus on February 09, 2012, 06:21:26 PM
I don't think end caps have much to do with structure.
They do. A very easy experiment at home: get a good assembled cardboard box and push from the side, before and after cutting away the ends.
I agree in theory, however, IMO the 4104 in particular, was so grossly overbuilt that it can take a tremendous amount of abuse and still maintain it's integrity.
The triple decker would be a little scary in the wind or on the freeway ramps, but it has room for the mother-in-law...
I would like to see it in a bus race, like on UK's "Top Gear" ;D
Here you go Top Gear bus racing
http://www.topgear.com/uk/videos/bus-racing (http://www.topgear.com/uk/videos/bus-racing)
Pip,
I think you miss the point, old GMCs are not square topped, they are round, and much stronger than a square metal top.
That is what monocoque construction is all about, the strength is in the cover and not an internal frame. Metal skinned airplanes are built like this, the skin is the structure.
A lot of that strength is in the round top and he has cut a very large hole in it.
#2, An end cap does not replace the cutaway ends of a bus, it covers over it much like the brick veneer around a house which contributes no structural strength to the house - it is just a cover. Since an end cap is just a plastic molding it has very little strength, it mostly changes the shape and look of the bus and provides some extra interior space.
Quote from: gus on February 10, 2012, 02:12:59 PM
That is what monocoque construction is all about, the strength is in the cover and not an internal frame. Metal skinned airplanes are built like this, the skin is the structure.
This isn't really accurate, unless American buses are much cleverer than I thought. Monocoques built from composite materials, such as yacht hulls and the latest airliners, are as close as you get to a large 'stressed skin' structure, but even these have an internal frame in some areas. It's true to say that the skin of a bus contributes to the stiffness of the monocoque, but it adds very little strength - it's the internal frame that does that. Take the skin off and the bus would still work - leave the skin and remove the frame and it certainly wouldn't.
Previously on here (mostly in discussions about slide-outs) people have likened a bus monocoque to a Coke can, and said things like "cut a hole in the side of a Coke can and it collapses". This is true as far as Coke cans go, but they really aren't analogous with bus bodies. Coke cans are a rare example of a thin-wall metal monocoque with no internal frame, and they work because the skin is supported by the gas pressure inside the can. Bus bodies have a substantial internal frame, and if you alter that frame appropriately you can cut any size holes in the side that you wish.
Jeremy
Back in the '70s, nearly all of Brewster's MCI buses (Couriers, MC1s, 2s, 3s, 5s, 7s and 8s), had sky-view windows installed along the whole length of the edge of the roof. Those were big. Several of the frame ribs were cut off to do it. The glass was certainly not structural: the only thing holding it up was the rubber molding. I don't remember any problems associated with that. I still have my Courier 96 with sky-views, and I don't have any structural issues after 55 years.
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fi582.photobucket.com%2Falbums%2Fss267%2Flostagainphoto%2FIMG_3417.jpg&hash=90adf09cc2f91f1039737fd4faafee4a2aee963d)
JC
Jeremy,
I completely disagree with you on every point. Monocoque construction by definition means the skin has the stress. The internal ribs or formers you talk about primarily give shape to the body, not strength. Practically every metal skinned light aircraft, in addition to airliners, uses this method. This is totally different from an internal structure such as in a fabric covered aircraft.
I don't know about all buses, especially the square shaped ones, but the metal part of all the old GMCs used pure monocoque construction, there was no structural frame as in a school bus. The central body was built and then the front end piece was hung onto it. The plywood floor is also part of this monocoque, sort of like a walnut shell, although there is a framework that holds the plywood pieces.
It's wrong to say "Monocoque construction by definition means the skin has the stress." - the word 'monocoque' is French for 'single shell' - nothing to do with a stressed skin as such. The shell consist of a skin on a framework - on a bus the skin is only stressed insofar as it gives stiffness to the frame underneath it - that's all it does and all it can do, given how thin the material is. The composite skin of yacht or modern airliner is a much thicker sandwich material and does take all the loads in most areas.
When you say "...all the old GMCs....there was no structural frame" - do you really mean that? I'm sure I've seen lots of pictures of tubular steelwork under the skin of GMCs, and I certainly have under lots of other monocoque buses. But maybe those old GMCs are much cleverer than I thought.
Jeremy
Let's make sure we aren't arguing over a difference in common understanding between British and American vocabulary or restricting it to industry-restrictive meanings.
http://www.merriam-webster.com/dictionary/monocoque (http://www.merriam-webster.com/dictionary/monocoque)
mono·coque noun \ˈmä-nə-ˌkōk, -ˌkäk\
Definition of MONOCOQUE
1: a type of construction (as of a fuselage) in which the outer skin carries all or a major part of the stresses
2: a type of vehicle construction (as of an automobile) in which the body is integral with the chassis
Origin of MONOCOQUE
French, from mon- + coque shell, probably from Latin coccum kermes — more at cocoon
First Known Use: 1913
http://en.wikipedia.org/wiki/Monocoque (http://en.wikipedia.org/wiki/Monocoque)
Monocoque (pronounced /ˈmɒnɵkɒk/ or /ˈmɒnɵkoʊk/) is a construction technique that supports structural load by using an object's external skin, as opposed to using an internal frame or truss that is then covered with a non-load-bearing skin or coachwork. The term is also used to indicate a form of vehicle construction in which the body and chassis form a single unit. The word monocoque comes from the Greek for single (mono) and French for shell (coque). The technique may also be called structural skin, stressed skin, unit body, unibody, unitary construction, or Body Frame Integral. A semi-monocoque differs in having longerons and stringers.
(follow the link for much more discussion)
http://en.wikipedia.org/wiki/PD-4501_Scenicruiser (http://en.wikipedia.org/wiki/PD-4501_Scenicruiser)
The GMC PD-4501 Scenicruiser, manufactured exclusively for Greyhound Lines, was a three-axle monocoque two-level coach used by Greyhound from 1954 to the 1970s. It was introduced in July 1954, and in total, 1001 were made between 1954 to 1956.
(more at link)
It did occur to me after my earlier post that when Gus said "GMCs have no frame" what he meant was that they had no chassis, and perhaps by 'skin' he means the frame of the shell, not the skin on the frame
Jeremy
Jeremy, you got it right the GM's have plenty of uprights and roof trusses just no chassis frame,you need to see one it's scary the engine hanging from the roof but it works and has for a long time lol
good luck
I think the Wiki entry is incorrect. To the best of my knowledge, GM buses were always referred to as semi-monocoque.
len is right of course...
as webster says only a portion of the load is carried by the skin, something we kept in mind while working on my brothers 4106.
the main load is carried by all that inside framework, etc. Unless it's a GMC school bus.
Looks like something I might do! Why because someone said: You Can not! Outside the Box. I am sure the builder paid attention to stress points and probably had that covered before cutting hole for mod. At least that is the way I approach doing something by doubling area stress/strength by 2x . Gm and MCI 's have been doing the rear engine sling thing for 60 plus years. I know BK had one just about fall out MCI due to a failed weld but not necessarily a design flaw. Observation only. Bob
Nusa,
I couldn't have said it any better.
Len,
You are correct, it is more of a semi-monocoque because the floor does have a framework. You will also note that I said the metal part is monocogue in that the skin is, indeed, stressed and is the primary structure of the bus. The real meaning of monocoque is stressed skin. These buses have no frame either underneath or on the sides. Again, the wall posts are there primarily to give shape to the metal, the skin carries the load.
This is more obvious in airplanes. If you look at the structure of a fabric covered lightplane compared to a metal covered one you will see that the metal one has very little interior framework.
Unibody automobiles are not monocoque. A unibody has a molded and welded sheet metal bottom framework which replaces the separate frame so it is one piece instead of two. This is done to eliminate body to frame twisting and is much stronger than the old two piece system.
Unibodies are more like a walnut shell which has interior webbed structure which provides a lot of its strength so the skin is not carrying most of the load.
Stressed skin is the point.
I realise this is an Eagle, but it does go to show that some monocoque (or semi-monocoque etc) buses aren't reliant on their skins, and can be driven about without them. I don't know how much the frame of a GMC differs from an Eagle, or whether it's skin is really any more important.
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fi374.photobucket.com%2Falbums%2Foo182%2FSongman64%2FMy%2520Buses%2F1989%2520Eagle%252020%2F4.jpg&hash=e95ae6e3fec26d3b737eaa987e2e31da26127b66)
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fi374.photobucket.com%2Falbums%2Foo182%2FSongman64%2FMy%2520Buses%2F1989%2520Eagle%252020%2F5.jpg&hash=6ef613ec61f14cc8cf1ad2e4b8824052cf9ed672)
Jeremy
The Eagle is dramatically different from the GM buses. It is not monocoque at all, but has a frame and a bridge like structure. It will stand without any skin at all. A GM in that same condition would buckle and the engine would be on the ground. There is no comparison between the two.
Jeremy, seeing those photos of the Eagle naked reminded me of two summers ago when I drove our MCI 9 looking exactly like that. :) Good times. Coach was just fine driving around like that...amazing.
Quote from: Len Silva on February 13, 2012, 04:34:31 PM
The Eagle is dramatically different from the GM buses. It is not monocoque at all, but has a frame and a bridge like structure. It will stand without any skin at all. A GM in that same condition would buckle and the engine would be on the ground. There is no comparison between the two.
Ok; in that case I can't really envisage what a GMC looks like at all.
When you say and Eagle has a
"frame and a bridge like structure", it is probably technically correct to say that that isn't a monocoque, but I think the industry does universally refer to this arrangement as such - I can't really think of another word which is used to distinguish buses with 'spaceframe' chassis from ones with 'ladderframe' chassis.
The picture below is of the chassis of a Mercedes 'monocoque' bus, as it is delivered to the bodybuilder. Clearly the chassis frame doesn't do much more than hold the front and rear ends together for delivery purposes - it doesn't gain any strength until the bodyshell 'bridge' is built over it. I assume that this is more-or-less how an Eagle is built too, but that, because everything is built in one factory, the bottom-most 'chassis' bit is built into the bodyshell frame from the word go, and the mechanical bits attached as separate elements.
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fbrt.mercedes-benz.com%2Fcontent%2Fmedia_library%2Fbrt%2Fmpc_brt%2Fhome%2Fmore_mb%2Fpublications%2Fchassis_chile_715x280.object-Single-MEDIA.tmp%2Fchassis_chile_2011.jpg&hash=ff5e63b33ade76828c9effca727d07cb65c4d5a1)
Jeremy
The post a above prompted me to find a picture of the chassis under my bus. The fuel tank is further back and on the other side on mine, but that's the only difference I think.
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fwww.payhost.net%2Fbedford_chassis.jpg&hash=6f7d584e59ed962a1f9f0dd923efcc366ab8ed53)
I used to see these being driven up the motorway to the Plaxton factory just as shown here, with just a temporary windscreen in front of the driver. Obviously it's a full-fat traditional ladder-frame chassis, and yet I doubt the bodyshell of my bus has any less steel in it than shown in photos of the skinless Eagle - which shows the advantage of a monocoque design I suppose. I got quite close to buying a monocoque Bova Futura at one stage, but the dealer selling it actually advised me to look for a traditionally chassis'd bus instead - he spoke of windscreens falling out if the bus was jacked-up in the wrong place.
Jeremy
One main difference in the old GMCs and newer buses is the round top. A round top has far more strength than a flat one. This makes it partly a cylinder and not just a square metal box.
Obviously cylinders are stronger than cubes.
Jeremy,Eagle like Len said are a truss design you can remove all the skin , take the bays and bottom floor out and drive down the road no other bus can you do that with
I saw a guy's cut the floor of the bays from a MCI and a GM it was not a pretty sight I also saw a Prevost XL a shop cut all the floors from the bays it buckled in the middle and was sold for scrap we bought the front clip.
GM's are built well but they scare me with all the weight hanging from the roof
Jeremy,
Is that an upright engine I see in your bus? If so, that's giving me some ideas for potential mid-engine Crown and Gillig repowers . . . How high is your floor off the ground, and how much width do you have between the frame rails?
John
Hi John
Yes the engine (Bedford 500 Turbo) is certainly upright. I'll need a tape measure to answer the other questions...I'll be back...
Jeremy
Ok, I removed the floor panel above the engine and measured there:-
- Height of top surface of floor from ground - 1090mm
(the floor panels are quite thick (lots of sound-proofing as you would expect), and the bottom surface of them is very close to the engine - only 40mm or so from the rocker cover)
- Width between chassis rails at narrowest point (inner edges of top flange) - 860mm
(there's actually more room than this implies with the measurement between the chassis side walls being more like 1000mm. But having said that, the engine sits well within even the 860mm measurement, with lots of space around it).
Hope that helps
Jeremy
Thanks, Jeremy. Us few full-frame folk need to stick together!
John
Yeah, it does make one pause thinking about all the weight in the engine comp hanging from the roof and six bolts!! Actually, it is probably four bolts since the lower firewall bolts don't appear to support much of the total weight.
However, never heard of one falling off but considering ,the ages of these old timers and Al corrosion possibilities, it could happen.
Never had to worry about that with my 4104 because it keep things well oiled!!