| Author | Message | ||
| Garth C. Burt (Gcburt) (209.248.25.239)
Rating: |
Looking at various pics - I notice that Eagle put their tag axle in front of the drivers - whereas everyone else seems to put them behind the drivers. Anyone know the reason or benefits of either configuration? Also - does anyone know of a bus with two driving axles (like eighteen-wheelers)? | ||
| Ace (172.157.51.85) Rating: N/A |
When the tag is in rear of the drive axle it will give you a shorter turn radius making for getting in and out of tight spaces easier. Eagle once did this when they made the model 01 but have since put the tag in front. Our H3 has a tag axle that can actually be air lifted to accomplish the same thing. Ace | ||
| Niles (4.4.117.34) Rating: N/A |
garth - "tag" axle in front of drive is a "bogey" - and 01 eagles had tags - one detriment is the need for a miter box - hopefully some others will tell you about twin screws - Niles | ||
| Garth C. Burt (Gcburt) (209.248.25.163)
Rating: N/A |
Niles - thanks for the explanation "tag verses bogey." I'm here to learn - BTW - what is a "miter box?" - Garth | ||
| ron rice (24.17.87.171)
Rating: N/A |
MCI built an MC7 that was a comi vehicle for some of their line carrier customers. The front half of the bus was like a normal MC7 passenger coach and the rear half was cargo space. There was a door in the side of the bus above the drive tires. It had the tandem rear axles much like a truck would have. Ron | ||
| Gary McFarland (Gearheadgary) (68.252.126.82)
Rating: N/A |
Man, I'd like to see one of those. gary | ||
| Marc Bourget (209.142.38.81) Rating: N/A |
The Yahoo MCI group has a picture of a trio of MCI-7s in the photo section. They had a unique front and a 3 tier roof IIRC. I've seen two on different occasions at MAK conventions. Marc | ||
| Fred (65.150.212.149) Rating: N/A |
Marc The 7 combo. did not have a 3 step roof. Only the 6 had this set up and was very hard to convert. Also the 6 was all S.S. and very heavy. I have coverted a combo unit and they are a very good coach. | ||
| Doug (69.244.108.42) Rating: N/A |
Cobo MC-7's had scenicruiser drivelines hence the dual duals | ||
| J.L.Vickers (209.169.106.163) Rating: N/A |
MC-7C Greyhound combo buses were not built by MCI but were MCI MC-7's converted by the Blitz company in Chicago,IL. Greyhound had them converted for hauling package express. The engine and transmission and rear drive axle and tag axle were removed from the PD-4501 Scenicruisrs. These Greyhound MC-7C coaches also had a automatic transmission instead of the 4 speed standard transmission. I am not sure of the number of MC-7C coaches that Greyhound had. J.L.Vickers | ||
| Marc Bourget (209.142.38.81) Rating: N/A |
FF, I read that one carelessly, I don't recall ever hearing of a -7 combo. Guess its what I get for trying to post at 2:00 AM, and no, I had not just crawled back home from a bar! No excuses for this one! Just an explanation related to insomnia! Thanks JL for the addn'l history. Onward and Upward Marc Bourget | ||
| Marc Bourget (209.142.38.81) Rating: N/A |
Garth re Mitre Boxes This is a geared device for delivering power to a forward facing drive axle from a power source (an engine) from the rear. It's distinct from the front axle unit of a double drive axle setup where they pass thru the drive shaft to the rear drive axle. I am told you can't use a front style in place of a mitre box but simply accepted the statement without investigating why. There are a variety of these boxes and are typically seen in MCI-5s and Eagles, IIRC. (I've never looked at one or seen a picture, just trying to help since nobody responded to your request) They're also used with the front discharge style cement trucks with rear engines. I am told that they are made by two mfgs and are built up from sheet stock and machined and not cast. The heavy duty models will have internal oil pumps. I understand that they differ as to amount of offset from the centerline of the pinon and angle of position, kinda like the face of a clock IYKWIM. Sorry, I don't have a better grasp on the technical terms, the "discussion" was awhile back and I didn't take notes. Take it FWIW! Onward and Upward Marc Bourget | ||
| Marc Bourget (209.142.38.81) Rating: N/A |
FF, JL and Garth, I read that one carelessly, I don't recall ever hearing of a -7 combo. Guess its what I get for trying to post at 2:00 AM, and no, I had not just crawled back home from a bar! No excuses for this one! Just an explanation related to insomnia! Thanks JL for the addn'l history. to Garth re Mitre Boxes 've never looked at one or seen a picture, I add the following just trying to help since nobody responded to your request This is a geared device for delivering power to a forward facing drive axle from a power source (an engine) from the rear. It's distinct from the front of a double drive axle setup where they pass thru the drive shaft to the rear drive axle. I am told you can't use a front style axle in place of a mitre box but simply accepted the statement without investigating why. I think it involves limits on the amount of torque rear yoke can accept but don't quote me. (mentioned only to prompt discussion) There are a variety of these boxes and are typically seen in MCI-5s and Eagles, IIRC. They're also used with the front discharge style cement trucks with rear engines. I am told that they are made by two mfgs and are termed "boxes" because they are welded construction, built from welded sheet stock and machined and not cast. The heavy duty models will have internal oil circulating pumps. I understand that they differ as to amount of offset from the centerline of the pinon and angle position, kinda like the face of a clock IYKWIM. Sorry, I don't have a better grasp on the technical terms, the "discussion" was awhile back and I didn't take notes. Take it FWIW! Onward and Upward Marc Bourget | ||
| Gus Haag (Mrbus) (205.188.116.135)
Rating: N/A |
I think you are confusing the "Drop Box" with the "Mitre Box". The drop box is the device that transfers the engine power to the drive axel. Very similar to a transfer case on a four wheel drive. You will notice that Eagles after the O-1 have the engine off set to the left side of the frame to get a direct drive to the drop box from the transmission. The Mitre box is mounted just inside the rear bumper, and allows the engine revolutions to be angled to a 90 degree to drive the original bus AC on one side and the fan and alternator drive on the other. Another reason for the dead axel in front of the drive was to allow space between the wheels for mounting the bus AC system without using up any bay space. As far as twin screw drives, the Crowns use it, as well as the 4501 and the MC7 Combos. Gus Haag | ||
| Stan (68.150.152.113) Rating: N/A |
Further to Mr. Vickers comment: The MC-7 combo was not a twin screw but a tag axle with dual wheels. Greyhound had 100 late 72 and early 73 (end of production) busses converted as prototypes. They made MC-8 combos as a production unit and ran hundreds of them in Canada. Marc. Miter boxes are used as fan hubs and on an eagle there is one behind the engine for the fan driveline. They have miter gears in them so they make a 90 degree turn between the input shaft and the output. The gear box on a front facing bus differntial is a dropbox which just uses spur gears with the input and output shaft in the same plane. On the MC-5 the pinion shaft sits at a angle (more than 90 degrees)to the crown gear so there is no change in angle in the dropbox. | ||
| John Rigby (65.112.227.94)
Rating: N/A |
I thought a drop box was a means of allowing the engine to sit on the opposite side of the rear end in put. So the engine drive shaft would go over the differential into the drop box and gears transfer the power down and into the front of the diffrential. Over down and in. Unlike the MCI 8/9 etc were the drive shaft goes from the engine and stabs straight into the diffrential John | ||
| J.L.Vickers (209.169.106.163) Rating: N/A |
PD-4501 Greyhound Scenicruiser was not a twin screw drive. The drive axle was the forward axle.Rear was the tag. Also as John Rigby said a drop box is used on the MC-5's and some Eagle models. Also some of the late MCI 40ft 2 axle coaches. The drop box is not the same as a miter box. J.L.Vickers | ||
| Gary McFarland (Gearheadgary) (209.128.79.46)
Rating: N/A |
"I thought a drop box was a means of allowing the engine to sit on the opposite side of the rear end in put." Really? they don't just flip the axle? Gary | ||
| Stan (68.150.152.113) Rating: N/A |
Gary: When there is not enough room for a driveshaft between the transmission and differential they set the differential facing forward. They then set the engine at an angle to the bus so that the driveshaft could go over the top of the axle beside the pumpkin. The spur gears in the dropbox then transferred the power down to the pinion shaft. | ||
| Gary McFarland (Gearheadgary) (209.128.79.46)
Rating: N/A |
Ah...OK, I get it. Thanks for the explanation. Mine is so close there is no "Driveline" per se, but just a pair of slipyokes, back-to-back. Gary | ||
| Marc Bourget (209.142.38.81) Rating: N/A |
Sheepish Marc I got to get back on a regular sleep cycle. Even my AM stuff is suffering. From Niles' post I believe I had the concept, but not the proper term Niles said: "tag" axle in front of drive is a "bogey" - and 01 eagles had tags - one detriment is the need for a miter box - hopefully some others will tell you about twin screws - Niles " I was associating the "bogey vs tag" compelling the need for a miter box (and reference to "twin screws") and jumped from there to the "drop box" and made an A _ _ out of myself in the assumption. I should take a break for awhile! LOL!! Onward and Upward Marc Bourget | ||
| Marc Bourget (209.142.38.81) Rating: N/A |
Dear Gearhead, It's Mid-day, after a "power nap" so hopefully I can keep it together better than above. As I understand it, the difficulty associated with short drive shaft lengths is the service life limitation on the universal joints (assuming maximum angularity limits are not exceeded) If airbags (do you have a Crown?) stay on top of the rear leveling valve(s) adjustment and avoid potholes etc. and I'd expect you won't bump up the stock dividends for U-joint mfg's too much! IIRC, Class 7 trucks went to airbag suspensions some years back. Some assumed it was for ride quality but the article I recall reading said the switch to airbags made the ride quality worse. The comment was explained by the need to maintain driveshaft angles in use. From another view, I've never asked anybody about whether longer driveshafts provide some torque "absorbtion" reducing driveline stress. FWIW, YMMV. Marc Bourget | ||
| Gary McFarland (Gearheadgary) (209.128.79.46)
Rating: N/A |
I think by the nature of a short-near-nonexistant driveline, angularity is pretty much a given. I have a bluebird Pusher (Ex-Transit). In reference to the original post, I have somewhere a picture of an ancient 10-wheeler, with tandem rears. Maybe gillig-looking. Hey, crowns make 10-wheelers, right. I think tandem drive axles on a bus are cool as hell, just not very practical. Gary | ||
| RJ Long (Rjlong) (67.181.236.27)
Rating: N/A |
OK, Gary, here's both a Crown AND a Gillig tandem pic for you. . . and yes, both axles are driven - they're standard OTS HD truck rear ends!   Enjoy! RJ PD4106-2784 Fresno CA | ||
| TWO DOGS (65.179.200.206) Rating: N/A |
school bus gary...now ask why nobody uses all drive axels.. | ||
| Gary McFarland (Gearheadgary) (209.128.79.46)
Rating: N/A |
I think I already mentioned that tandems were impractical, but they're still tuff-looking. The photo I have is like from the 40s/50s and maybe a troop transport or something. tuff as hell. I love crowns. Gary | ||
| jimmci9 (209.240.205.60) Rating: N/A |
little more terminology... if a non-driving axle is in front of a driving axle, its called a "pusher"... if a non-driving axle is behind a driving axle its called a "tag... "bogey" is slang for a tandem or tridem axle set-up... | ||
| Niles (4.4.115.60) Rating: N/A |
Garth and Marc , NILES<<<<<<IDIOT - Sorry I should edit my posts before actually posting - don't know why I used Miter - meant drop box - sorry for screwin it up - thank god not all busnuts are as sloppy as me and corrected it - I hate giving or recieving misinformation - thanks all for correcting me - Niles | ||
| John Rigby (24.174.238.253)
Rating: N/A |
Boy that crown looks good. John | ||
| Garth C. Burt (Gcburt) (209.248.25.232)
Rating: N/A |
Y'all, I appreciate all the responses and the education I'm getting (BNO newby). I am still interested (if anyone has an idea) of why Eagle used their non-driving/weight bearing axle in front whereas everyone else seems to use them behind the driving axle. Garth | ||
| Phil Lyons (209.86.100.235)
Rating: N/A |
Greetings, Those combo tag axles do look awfully cool. Maybe I'd give up some "practical" for fun. I have an MC9. Could the tag on that be turned into full tag? or would $$$ be out of control? Anyone done something like that? Best Regards - Phil | ||
| Marc Bourget (209.142.38.81) Rating: N/A |
Garth, I think it's a function of how far the tail hangs out past the last axle. Eagle chassis being heavier than the other designs, it's possible that they counteracted the weight to reduce the load on the front axle (often near load limits) by sticking the engine package a little more to the rear. (Just speculation, btw) This would "permit" using a rear drive axle without suffering u-joint angularity problems. FWIW, YMMV Onward and Upward Marc Bourget | ||
| TWO DOGS (63.185.73.154) Rating: N/A |
yeah..guess it's weight..reason for the tag... the 01 was one way..rear tag..the 05 was 'tag' in front..then ..catskinner took an 05 & switched them around again when he put the cat engine in...my Eagle is 28,000 pounds....most 4104's are about 20,000 I think... | ||
| Marc Bourget (209.142.38.81) Rating: N/A |
Dear Gearhead Resurrecting your question/point about "flipping" the axle. I had a discussion about upgrading to 4 strokes in a GM with an automotive engineer who had major responsibilities for chassis and driveline with an OEM. "Back" in high school the trick move with VW transaxles destined for dune buggies, etc. was to flip the ring gear from side to side to reverse engine input rotation. Asked "why not" with larger axles like trucks. The reply explained that the teeth surfaces on ring and pinions in the drive or forward direction for Trucks are so highly loaded that they are specially heat treated for wear but the reverse or backside of the teeth are not, since the load/time in use - is so low, they save the expense. To have the "backside" heat treated now would be very expensive. Much more than the cost of a drop box, or the $1800 for the kit to reverse the rotation in a 730/731, IIRC. Onward and Upward Marc Bourget | ||
| DrivingMissLazy (66.168.175.51) Rating: N/A |
My 1980 Eagle 10 had a "bogie" axle in front of the drive axle. Some time after that, Eagle changed their design and switched the bogie to the tag position. I do not know for sure when. Also, some of the earlier Eagles had tag axles and then they switched to bogie. I have never heard of the reasons why. On my 10, the gas tanks were above the bogie axle. Also, the mitre box, mounted to the rear of the engine had two output shafts at 90 degrees to the engine. These shafts were coupled to u-joints and drive shafts. Drive shaft to the right was used to drive the original bus A/C unit. Drive shaft to the left went to another right angle drive box with V-belt drive pulleys. One set of pulleys drive the hydraulic controlled fan. Another set of pulleys were used to drive a Drivers A/C compressor. I do not think that was original. I think they originally run an alternator. Richard | ||
| Phil Dumpster (24.17.4.245) Rating: N/A |
You wouldn't be able to do the differential flip in a V drive setup anyway. The input shaft of the axle would point towards the drivers side of the coach. If you want to go to a clockwise engine in a V drive, your best route is with a transmission designed to take a clockwise engine, such as the Allison VR, the Voith, or the ZF. (As an aside, the Voith is one weird gearbox.) Only the engineers who designed the various Eagle coaches would know the specific reason why they went with the setups they used, but I would venture a guess as to why they changed to a rear axle drive setup with the later coaches - probably to reduce the tendency of the coach to rock fore and aft. In an asymetrical bogey setup, one axle carries more weight than the other. In a symetric bogey, both axles (should) carry the same amount of weight. Visualize an imaginary line between the axles where the coach would pivot on a single rear axle. In the asymetrical setup, this line will be closer to the axle that carries more weight. From a drivers perspective, consider this line to be the effective rear axle. Move this line backwards, and you lengthen the effective wheelbase. Lengthening the wheelbase reduces the tendency to rock fore and aft. You never see RTS coaches doing the Eagle shuffle for this reason. Unfortunately, lengthening the effective wheelbase also increases the turning circle, but this can be mitigated by changing the front end geometry to compensate. | ||
| Gary McFarland (Gearheadgary) (209.128.79.46)
Rating: N/A |
"...the trick move with VW transaxles..." I have some buggy/sandrail history too, this is where I've personally done it. My Father-in-law was involved in the early formula Vees and they used the same technique. "are specially heat treated for wear but the reverse or backside of the teeth are not....Much more than the cost of a drop box..." Mine is a flipped Rockwell SQHD, as are many others. Gary | ||
| Gary McFarland (Gearheadgary) (209.128.79.46)
Rating: N/A |
See Marc, you made me nervous. My axle is flipped, and I have to regear, I'm worried that my gearset is "Special" and I may not be able to find the ratio I need for a sane price. Fortunately, I am surrounded by automotive engineers, and I posed the question about heat treating one face an not the other. The resident "Answer Guy" said: "Heat-treating gears is a fairly cheap process, and I guess it's possible to treat only one face, but I don't know why you would." I explained what the issue is, with a transfer box, instead of flipping the axle and mentioned what you said: 'To have the "backside" heat treated now would be very expensive. Much more than the cost of a drop box' His response was: "That would not be a true statement". Do you have any more data on this? Anybody else heard of this? Although the "Answer guy" is famous around here for knowing everything (He really is a knowledge-sponge) I'd like to learn as much as possible about this since I'm on the verge of a ratio change. Thanks, Gary | ||
| Gus Haag (Mrbus) (152.163.100.132)
Rating: N/A |
I posted concerning this discussion a couple of days ago, but I guess somehow I screwed it up. While talking with an Eagle engineer several years ago, I asked the question of why the difference in the Mod. O-1 and the O-5 axel location. His answer was to allow room for the AC system without giving up any bay space. Sounded right to me, as everything except the compressor was mounted between the pusher axel wheels. Gus Haag | ||
| Gary Carter (68.25.26.242) Rating: N/A |
The main reason for the tag moving ahead of the drived axle and becoming a bogie was bay space. Eagle moved the fuel tanks between the bogie, and increased the luggage capacity to compete with the GM 4905 (which also had a bogie the driver could raise). Follow the money. More bay space equals more payload either in passenger luggage or freight. | ||
| Marc Bourget (209.142.38.81) Rating: N/A |
Gary I repeated what I remembered as I recalled it. I don't know how accurate my recollection is. Like most posts I make, unless I quote a source, (Galey, Smead, the Glacier Bay site, for example) I'm offering the info or opinion to expand the discussion not because I think I'm the end all or be all of bus conversions. The experience I related occurred in like a mentor/student situation. Nothing like sales puffery there. Upon reflection, I don't believe we were talking about your style axle and YMMV. Also, while I mentioned "heat treat" the discussion did touch on surface treatments and I was negligent by not including mention of this, but again, I was "expanding" the discourse not pontificating. I'm not sure of the heat treating technique. For something like the "asymetric" treating of a ring gear I guess it would probably be something like induction hardening. Typical "soak" HT process would see the whole gear assume the same hardness. Induction hardening (or a similar process) seems like the better path since you would achieve a hardened contact area but leave the balance of the gear softer or less "brittle" and better for accepting stress and esp. shock loading. As for economics, I doubt local HT facilities would have the robotic equipment and doing individual teeth "by hand" would be pretty labor intensive. Easier to buy the "flipped" gearset. I'll be able to touch base with my friend this weekend and I'll try to resurrect the discussion with him. Onward and Upward Marc Bourget | ||
| Marc Bourget (209.142.38.81) Rating: N/A |
As a kinda "cute" aside, my first recollection of the use of the acronym was by JJMaxwell, I believe and was used in the context of "Your Mileage May Vary" but it could also be used for "Your Memory May Vary" FWIW Marc | ||
| Gary McFarland (Gearheadgary) (209.128.79.46)
Rating: N/A |
Marc, Any word on this? I'd like to know what you found out from your friend. Gary | ||
| Jim-Bob (12.46.52.74) Rating: N/A |
Only VERY FEW 4905s had bogie axles. The bus doesn't need it due to superior design & materials. (Monocoque design, mostly aluminum.) | ||
| FAST FRED (4.245.191.156) Rating: N/A |
No question there of superior design & construction , but as a RV Camper its fairly easy to get to the axle rating. Folks doing a 2 axle 40 ft coach of ANY mfg need to be very aware of every pound. That marble jaccuzi , that granite sink , and heated concrete floor are better left to the 3 axle conversions . FAST FRED | ||
| Marc Bourget (209.142.38.81) Rating: N/A |
Gary, Got to talk to him but forgot my promise. Maybe next weekend! Sorry for the oversight Marc | ||
| Gary McFarland (Gearheadgary) (209.128.79.46)
Rating: N/A |
When you get a chance, a regear is approaching the center of my radar. Thanks, Gary | ||
| Marc Bourget (209.142.38.81) Rating: N/A |
Dear GHG Re my post that the heat treat on one side of a ring gear precluded "flipping" it to permit reverse engine rotation or reverse placement of the axle in the chassis. You countered this saying your engineer friend claimed that heat treat is "heat treat" and it "soaks" thru and direction of rotation shouldn't make a difference. That post, to the limits of its applicability to this issue was correct. I've contacted my original source and here's the "Rest of the Story" The "Rest of the story" relies upon the fact that Ring Gears are typically Hypoid Gears with major and minor arcs. The ring gear, like I mused, is typically induction hardened on only one side, the major or outside radius. This gives better face wear and leaves the rest of the mass of the gear less crystalline and in better shape to absorb transient (read shock) loadings. The ring gear is also "soak" heat treated to increase its strength, but not to the point that the crystaline properties get too pronounced. Flipping the ring gear to reverse direction puts the load on the minor or cove side. Load per unit-area is increased and the mechanical ratio is increased as well due to the lesser curvature. The light loading of a VW ring allows the enthusiast to ignore the above. It's a much more significant issue with Bus/Truck sized differentials. So, I either forgot or we didn't get into the major vs. minor arc discussion in my original conversation. sorry for the oversight. FWIW Onward and Upward Marc Bourget | ||
| Gary McFarland (Gearheadgary) (68.252.9.211)
Rating: N/A |
Man, I hope you are wrong, I have to buy some new gears, and that would drastically reduce my options. Gary | ||
| Don/TX (66.82.9.26)
Rating: N/A |
Interesting that nobody mentioned the converted Eagles that have had the "dumb" axle removed. The several owners I have encountered have been very pleased with the conversion, not only from increased cargo space, but a superior ride (with air bags of course). I have driven both 01 and 05 eagles, and I want to report that the 01 has a MUCH shorter turn radius than the 05. | ||
| Gary McFarland (Gearheadgary) (209.128.79.46)
Rating: N/A |
Oh for crying out loud. As I was explaining my dilema to another automotive engineer here, trying to get an answer to the "Hardened Face" question, I realized: THE GEAR ROTATION DOESN'T CHANGE Oh for chrissakes. That's what happens when you just read a post and don't think it through yourself. I already knew this. That's why there is two different oil fill locations. Gary | ||
| Jim-Bob (12.46.52.74) Rating: N/A |
Gary, looks like the only issue is would you remove the axle housing & turn it around so that the driver's end is now on the pax side or would you "roll" the housing so the ends would stay the same but the "pumpkin" opening faces rear instead of front (or visa/versa). Most axles have a long & short side. If you spin it, your long & short will reverse. If you "roll" it, they'd stay the same but mounting & oil fill/drain holes would be the issue. This is THE LONG & SHORT OF IT! (Couldn't resist.) | ||
| Gary McFarland (Gearheadgary) (209.128.79.46)
Rating: N/A |
I'm not changing rears, only looking for a differend ratio gearset. Gary | ||
| Jim-Bob (12.46.52.74) Rating: N/A |
Well, according to the little sketches I made, the direction of rotation is the same for a bus or a dumptruck. | ||
| Gary McFarland (Gearheadgary) (209.128.79.46)
Rating: N/A |
Yeah, but you had to sketch it, right? I look at it like this-- you flip the whole drivetrain over pivoting on the axis of the axle tubes. OK everything is fine, rotation hasn't changed, but all of the oil is running out of the valve covers/breathers, so you rotate the engine/trans on the axis of the rotating assembly and life is good, rotation hasn't changed. Seems intuitive, but makes my brain hurt. Gary |
