| Author | Message | ||
| Jeff Pritchard (Jeffpritchard) (70.179.28.145)
Rating: N/A |
On the way home from work yesterday I saw an MCI bus (still in commercial service). It was a "fishbowl" style, but I'm not savvy enough yet to tell you guys what exact version of MCI it was. It had a tag. In most respects it seemed like a typical inter-city bus of maybe ten years ago. The strange thing was that the rear overhang (behind the tag) seemed to be very short, on the order of two feet or less. How did they get the engine and transmission between the back end and the drive axle? Whatever trick was used, why isn't it deployed on diesel motorhomes to reduce the long rear overhang? thanks, jp | ||
| CoryDane RTSII (66.155.188.84) Rating: N/A |
The Long rear end overhang on motorhomes is purposely designed to increase maneuverability in city driving. They have no desire to reduce overhang and lose maneuverability. School busses have the same design but I noticed on the RV show, the new RV's have an even greater overhang built on. I don't recall seeing a bus with much of an overhang designed into the coach unless the bus was modular (RTS). The 60 foot busses that hinge in the middle have the engine and trans under the floor. My understanding is the engine runs on its side to save space in height. cd | ||
| Lin (66.245.216.207) Rating: N/A |
The overhang on my Superior Supercruiser, which is essentially a school bus chasis, is about nine feet. It would seem to allow for narrower turns, but has the drag-ass problem approaching steep inclines. What is the average overhang on an intercity? | ||
| Jeff Pritchard (Jeffpritchard) (70.179.28.145)
Rating: N/A |
Thanks, but it depends on whether it's a gas or diesel MH. The long overhang on a gas MH is because the stock truck chassis that they are built on are relatively short. To make a longer MH they just extend the back end of the chassis with some welded on C channel. When this gets too extreme, it screws up the handling, and folks that are into MH comparisons like to chat about the wheel base to overall length ratio when discussing the handling characteristics of a MH. If it gets below about 50%, then the very long overhang is going to cause significant handling problems (fishtailing and the like). I was talking about Diesel MH though. It was explained to me that the engine is at the very back, then the tranny, and then the rear axle (all layed out in one plane, mostly below floor level, but with some of the engine hiding under the bed or a raised rear closet). It's supposedly difficult to build a short Diesel MH that has good handling, because the rear overhang has to be a certain length to get both the engine and tranny in there. That means a shorter wheel base, and thus you wind up with the problem describe above that is common with long gassers. So, I'm wondering why diesel MH manufacturers aren't able to arrange the engine and tranny like they apparently are in the MCI bus I saw, in order to make a short diesel MH with good handling (i.e. a wheelbase to overall length ratio that is well above 50%). Can anyone describe how the engine and tranny are arranged in one of these intercity busses with negligible rear overhang? thanks, jp | ||
| John that newguy (66.19.73.204) Rating: N/A |
That 12' or more overhang on the standard 34'+ RV can be a real bother when you consider the overhang is measured from the rear axle pivot-point. You move the front end one foot to the right, and you're swinging that rear end quite a bit to the left. The notion that it's easier to negotiate turns, etc due to that "great wheelbase", is ill-founded, especially so in traffic. Give me a 40' bus any day. | ||
| FAST FRED (4.245.128.242) Rating: N/A |
RV's have tiny wheelbases so the first time driver feels OK, on his 5 first mile test ride. The huge rear overhang causes weathercocking in crosswinds , so there no fun to drive in a crosswind. There is an RV safty forum that claims short wheelbased coaches ( WB less that 50% or so of overall leginth)are very very dangerous. FAST FRED | ||
| Stan (68.150.152.113) Rating: N/A |
MCI busses only have about three feet between the rear wheelwell and the bumper. This still puts the drive axle ten feet or more ahead of the bumper. A large part of the engine and transmission are sitting between the wheels. The only other possibility is you saw a transit bus with cross mounted engine. MCI did build some transits but I don't think any had a tag axle. | ||
| Johnny (4.174.109.218) Rating: N/A |
"Thanks, but it depends on whether it's a gas or diesel MH. The long overhang on a gas MH is because the stock truck chassis that they are built on are relatively short. To make a longer MH they just extend the back end of the chassis with some welded on C channel." Actually, many times, especially on C's, the wheelbase is stretched. | ||
| Gary McFarland (Gearheadgary) (68.79.101.181)
Rating: N/A |
A stratch is a routine operation in the factory, there is a workstation in the production line just for the frame job. Gary | ||
| BrianMCI96A3 (69.34.171.129) Rating: N/A |
Actually, I don't know about the newer MCI's but a great number of MCI coaches (MC-9's 96A3's etc.) measure a little over 4 feet from the rear bumper to the trailing edge of the tag axle wheel well... I measured. | ||
| Derek (Derek_L) (24.83.196.239)
Rating: N/A |
Some of the (earlier) MCI 102D3's and Prevost H3-40's had VERY short overhangs, I'll see if I can get a picture one of these days. | ||
| Jeff Pritchard (Jeffpritchard) (70.179.28.145)
Rating: N/A |
I looked at some pictures online. Me thinks it was a 102C3 or 102D3. jp | ||
| Derek (Derek_L) (24.83.196.239)
Rating: N/A |
If it were one of those, the transmission output sits between the tag wheels. | ||
| Henry R. Bergman, Jr. (Henryofcj) (63.224.197.10)
Rating: N/A |
My Crown Super Coach 40 foot 3 axle 10 wheeler has somewhat of a rear overhang, but it appears the factory cleaned up the departure angle sooss usually the bumper does not drag on stuff. The mill is in the middle of the coach under the floor hanging from the frame positioned on its left side. The problem is right now the oil pan and power steering pump bracket kinda hang down... ...too low to the ground. That plus a transverse mud flap do-hickie thing on the bottom of the forward firewall that hangs down nearly to the ground. It is supposed to help suck air thru the side mounted radiator. Works too. Anyway, sooss far, sooos good. Have not yet smacked anything on the bottom of the bus. Hate to think how much a replacement pancake oil pan would be for a Big Cam Cummins. $Ouch$ Lack of ground clearance with a Crown remains a problem. | ||
| Johnny (4.174.109.115) Rating: N/A |
Were it me, I'd build a skidplate. Find someone scrapping an old dozer blade, cut it to fit, weld it together, & bolt it up. | ||
| Gary McFarland (Gearheadgary) (68.252.9.211)
Rating: N/A |
I have a picture in my mind of an extra axle to hold up your skidplate. I'm used to BIG Cats. Gary | ||
| Marc Bourget (209.142.38.81) Rating: N/A |
Naw, I'd do the skid plates in Magnesium, then you'd get all those spectacular sparks you see on the F-1 races and on TV and the movies! Onward and Upward | ||
| Johnny (4.174.103.29) Rating: N/A |
Like a bus (with a GVWR pushing 50,000lbs) can't hold an extra 100lbs or so of steel? Heck, I've seen them built out of cut-up dozer or front-loader blades on Jeeps. Just don't be dumb & mount them with four 7/16" grade 2 bolts like one idiot I saw. | ||
| Gary McFarland (Gearheadgary) (209.128.79.46)
Rating: N/A |
Yeah, I know--you meant a smaller blade than the one that sprang into my head. My first mental image of a dozer blade is more like 1,000 lbs. Where I grew up, D6 Cats are the little ones. Gary | ||
| Johnny (4.174.109.15) Rating: N/A |
I don't mean the whole blade--I mean making a skidplate from metal CUT from a blade. | ||
| Henry R. Bergman, Jr. (Henryofcj) (67.137.156.27)
Rating: N/A |
What I will probably end up doing is redoing the power steering mount which does hang down much lower than it really needs to. Looks like it can be raised safely about 3 inches, which may make a big difference. However, then the big 44 quart oil pan becomes... ....the primary target. But, in all the years Crowns have been around, I have not really heard of any big, bad horror stories.... ...of something really big bashing the oilpan. Then I see a Crown on E-bay with a "patched" Detroit Diesel block. Wonder what they hit? The Crown 10-wheeler stripped goes right at 14550 on the drivers and 9400 on the front. Others say handling is improved by... ...letting the front axle handle a little more weight than the expected 33% front and 66% rear. Seems this is commom with coaches. Luckly I have a 16K front axle and 12R 22.5 tires and wheels good for over 14000, the federal limit. CROWNS FOREVER!!  |