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Author Topic: Scenicrusier using the twin 4-71  (Read 5522 times)
wg4t50
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« on: June 08, 2013, 10:52:20 PM »

Have always heard of that setup, I even had to pleasure of riding on one from Winchester Va to Harrisonburg, Va about 1957, have been trying to learn more about that setup, driver control of both engines etc, how did they perform etc, etc.

In my business,(Generators) have came across a few twin DD setups, 6-71 a left and right about 2 inch apart, into common gear setup with two clutches, starters & governors.   Recall it is tuff to determine if one is not actually running under power until you get familiar and check for exhaust smoke & heat etc..

Question is? Did DD use the twin setup or actually two seperate engines ?  Have to guess it was the twin setup, one driveshaft etc..  In those days DD would and could design and make most anything.

Just trying to find some data on this old system before the V configuration was available.  Been most interesting to this gear head.
Dave M
« Last Edit: June 08, 2013, 11:00:24 PM by wg4t50 » Logged

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« Reply #1 on: June 09, 2013, 08:12:05 AM »

I talked to Derf Namyar our noted Scenicruiser historian who lives in OKC,OK.
He stated that the two 4/71's were in a "V" configuration 30 degree angle.
The right 4/71 engine started first with a electric starter and the left engine would then start through a fluid torque converter arrangement.
The transmission was a 3 speed with a 2 speed high & low clutch.
In the very early1960's Greyhound had all of the remaining 987 Scenicruiser's rebuilt with a 8V/71 engine and a 4 speed Spicer Transmission.
The Scenicruiser's went on to serve Greyhound for another 15 years in Trans Continental service
San Francisco/Miami through Scenicruiser Service no change of coaches.
New York/LA.
To this day the Scenicruiser is a Icon in the bus industry.
Eagle owners you have to thank Greyhound and GM Coach for the Scenicruiser.
Continental Trailways did not have a coach to match the Scenicruiser until Trailways had the Eagle Coach imported from Germany.
Hope this helps with your questions about the PD4501 Scenicruiser
jlv


The below message is from a retired Greyhound Driver

Twin Engines

 

The twin engines on the Scenicruiser did not last.  When properly synchronized, they were a dream to run, but out-of-sync, they were gutless.  I have seen them so badly out-of-sync, and so powerless, that it took first gear to top Devilís Elbow hill.  I followed an out-of-sync Scenicruiser from Springfield to St. Louis once (as double on the schedule), and that bus would not have made it up the long hill east of Gray Summit on local route 100 if I had not been following with a Silverside.  When I realized that the first section Scenicruiser was stalling out, I eased my Silverside up behind the Scenicruiser until the bumpers touched, The Scenicruiser driver stuck his hand out the driverís window and motioned me on.  That Silverside and me then pushed the Scenicruiser on over the hill.  That push was a "no, no" in the Safety Manual, but that violation helped us make it into St. Louis.

 

Out-of-sync engines were not always the fault of the shops.  We had drivers who thought they were also mechanics, and they delighted in making adjustments in the engine compartment, on the headlights, and on anything else they could find to adjust.  Before too many years, the twin engines were replaced by a single engine.  The two-speed button was removed, and the shifting arrangement went to four standard forward speeds.

 
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wg4t50
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« Reply #2 on: June 09, 2013, 08:20:04 AM »

Yes, thanks, I had heard the major issue was drivers,  A V config. Is indeed interesting.
Many thanks
Dave M
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luvrbus
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« Reply #3 on: June 09, 2013, 08:51:55 AM »

They were nothing special it was ran through a Twin Disc gear box with a torque converter those engines are still in use in the oil patch you even see it a quad setup 4-71 or 6-71's  

I bought a friend a set of of the twin 4-71's he wants to install it in his Scenic  you adjust the twins or quads with exhaust temperature get the same exhaust temp on all engines and they work fine get it off a 100 degrees only 1 engine will carry the load they have a test lead to plug in a pyrometer on the engines  

I still have a antique meter hanging on the wall to set those with a Greyhound mechanic in Dallas sold me for 20 bucks in 1962      

You can thank Greyhound and GM for the 8V71 they could never get in right using the setup for buses hence the 8v71 was born all this a little worthless trivia 

RRT the Eagle was born also because GM would not sell the Scenic to Trailways or any other operator hence came forward the law suits with the demise of the great Scenic what a shame     
« Last Edit: June 09, 2013, 09:07:16 AM by luvrbus » Logged

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wg4t50
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« Reply #4 on: June 09, 2013, 09:09:55 AM »

My lack of experience, have seen many Twin Disk arrangements, just never seen the V drive with two DD engines.
Thanks
Dave M
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« Reply #5 on: June 09, 2013, 09:45:07 AM »

RRT the Eagle was born also because GM would not sell the Scenic to Trailways or any other operator hence came forward the law suits with the demise of the great Scenic what a shame.

Kerrville Bus Company tried to lease a few Scenicruisers I can not recall the exact number.
Even though Kerrville Bus Company was part owned by Greyhound KBC buses even had the Greyhound dog on the side of their Coaches.
Greyhound still would not lease any Scenicruiser's to KBC.
So KBC bought 6 each new 01 Eagles. I bet that caused quite a crisis at Greyhound with perhaps a running dog on a Eagle 01 coach.
KBC was looking for 40 ft. Coaches for the military charters in the San Antonio,Texas area.
RRT

 
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RJ
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« Reply #6 on: June 09, 2013, 06:02:25 PM »

Clifford -

The Scenicruiser was an exclusive contract between Greyhound and GMC, very similar to Trailway's arrangement with Bus & Car for their Eagles.

The various lawsuits against GM T&C were not a result of the exclusive Scenic contract, it had more to do with the 2-stroke and their collusion with Firestone over on the transit side of the business to pressure the demise of metropolitan streetcar systems.

But the poor performance of the twin-fours in the Scenic, plus some chassis issues, really strained the relationship between GL & GM, thus leading to the rise of MCI, today's dominant intercity coach builder.

FWIW & HTH. . .

 Wink

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« Reply #7 on: June 09, 2013, 06:52:07 PM »

A lot came out of the anti trust law suit filed in 1954 settled in the 60's I think against GM  it open the door for other operators and bus makers no longer could GM control the bus market they once had they had to sell to all operators and sell the engines and drive trains to other builders as well

 I really enjoy reading Doc Rushing on the demise of GM titled Bluehounds and Redhounds about the hold they had on the bus market
« Last Edit: June 09, 2013, 06:55:14 PM by luvrbus » Logged

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« Reply #8 on: June 09, 2013, 09:10:04 PM »

I saw a drawing of the twin 4-71 setup, and in the drawing, the two 4-71's were layed over side by side-not in a V (course the drawing can be wrong). Thankfully GM came out with the V blocks to replace the twin 4-71's.

In the 40's and 50's, some truck drivers ran Buick straight 8's with Dynaflow transmissions back on the trailer. The engine would kick in at a pre set MPH and help push the truck over the hill-that is until some of them just kept going, which ended that. Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #9 on: June 09, 2013, 09:44:06 PM »

I was reading some old bus books tonight and came across the Pegaso Z-403 built in Spain before the Scenic came out here remarkable resemblance to the Scenic had torsion suspension, independent front axles,monocopue body,2 levels and mid ship engine a 1949 design a little ahead of the times one could say 

Would GM steal a design nah only the Chinese would do that   

good luck    
« Last Edit: June 09, 2013, 09:52:19 PM by luvrbus » Logged

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« Reply #10 on: June 09, 2013, 10:30:30 PM »

TomC,
I am guessing theVee configuration is actually the two side by side with sommon bell housing, not clear about the fluid coupling, on generator setups, there were twoover center clutches (2), blocks were very close to each other, a left and a right engine, sort of like a LA & RA setup, (I do not recall the actual config of blocks, think there were total of 8 for single blocks.  In those days Detroit Diesel made some very interesting configurations with the inline engines.  Sort a miss em days, maybe I miss what I could do in em days too.
Dave M
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« Reply #11 on: June 10, 2013, 07:08:12 AM »

Read more (what I could find) and one source said that unlike what was thought, the driver could not disconnect one of the engines and go down the road on one engine only. The right engine was started, then the left engine came up to speed through the torque converter with no disconnecting clutch in between the two. It was a good idea on paper since the V blocks had not been made yet. But-two 4-71's weigh in at 3,400lbs, plus the fluid drive to connect to the 3spd transmission made for a heavy rear end. Compared to the 8V-71 that weighs 2,350lbs. It's a good thing they switched. With all the structural problems the PD4501 had, with that heavy drive train, it would have been worse. Good Luck, TomC
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« Reply #12 on: June 10, 2013, 11:20:10 AM »

TomC, very interesting about the weight of the pair of 4-71 @ 3400, that is near the same as the 12V-71 I had in tbe MC7 and no structure issues, it was a concern, but never showed up.   As I have mentioned, the 12V fit like the bus was designed for it, since the MC6 did enjoy that engine, no surprise I guess.
Was a big boy toy !
Dave M
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« Reply #13 on: June 10, 2013, 12:56:22 PM »

TWIN COACH whoas many of you know had twin inline(layed over) six cylinder gasoline engines mechanically linked together. My late Grandpa worked for the old Transport Company(Milwaukee WI.) and he told me about how those things were hard to deal with. It was next to impossible to operaate the bus if one engine crapped out since they ran as one.( Who says things were always better in the old days)
TomC, you made me wonder now, was that BUICK straight 8 part of the trailer or a separate unit behind the trailer?
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« Reply #14 on: June 10, 2013, 12:59:52 PM »

Have always heard of that setup, I even had to pleasure of riding on one from Winchester Va to Harrisonburg, Va about 1957, have been trying to learn more about that setup, driver control of both engines etc, how did they perform etc, etc.

In my business,(Generators) have came across a few twin DD setups, 6-71 a left and right about 2 inch apart, into common gear setup with two clutches, starters & governors.   Recall it is tuff to determine if one is not actually running under power until you get familiar and check for exhaust smoke & heat etc..

Question is? Did DD use the twin setup or actually two seperate engines ?  Have to guess it was the twin setup, one driveshaft etc..  In those days DD would and could design and make most anything.

Just trying to find some data on this old system before the V configuration was available.  Been most interesting to this gear head.
Dave M



While not a 4-71 or a 'V', an old twin.

Sherman Tank Engine GM 6046 Twindiesel Fire Up
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« Reply #15 on: June 10, 2013, 01:42:54 PM »

As an independent shop I worked on a dredging boat that used the twin disc single output drive using two straight up 6-71 engines, a LH and  RH.  I had to rebuild the the left (LH) engine because the operators were trained to set the engine govenors by a pyrometer from each engine so that the exhaust temps ran the same.  That might of worked, but the left engine pyrometer wasn't working right so  they would adjust the left engine so hard that the stack would be blowing black while the right engine ran clean.  These guys weren't too bright, I had to take them outside and make them look at the difference in the exhaust color and they still wouldn't believe they were doing anything wrong because they trusted the pyrometers and that is what they were trained to do.

I finally convinced the owner the pyrometers weren't working right so he cut the pyrometer leads and let me adjust each engine to the same RPM's.  Problem solved, and this was the second time they had burned up the LH engine for the same reason.  The first shop that rebuilt the LH engine told them the same thing about the pyrometers and they didn't listen.

--Geoff
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Geoff
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« Reply #16 on: June 10, 2013, 02:12:27 PM »

You are supposed to check the rpm after setting twins,triples or quads when you finish setting with a pyrometer when set right the quads won't vary over 2 rpms between the 4 done that many,many times without problems  
 
Seems like the first shop should have checked the leads and probe Geoff you always replace those on a rebuild according to the DD bible 

One thing I did learn about using a pyrometer on a set of twins you pull the valve covers to be sure both engines have the same injectors only took me 4 hrs to figure out one had 70's and not 60's like the tag said

I did see a 2896 Waukesa destroyed one of three on a drilling rig deck because the driller told a deck hand to check the engines and he didn't know the difference between C and F in degrees a pryometer is a dangerous tool in the wrong hands a great tool if used right    
« Last Edit: June 10, 2013, 02:51:46 PM by luvrbus » Logged

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« Reply #17 on: June 10, 2013, 02:32:43 PM »

I don't pretend to know anything about this stuff, but this issue of having to balance the two engines together makes me think of twin-engined kitcars, which are all the rage at the moment. These typically use two engines from high-performance motorbikes such as Honda Blackbirds or Yamaha R1s, driving through a custom transmission that links the engines together - but the bit which is relevant to this discussion is the fact that both engines still each retain their own gearboxes, specifically in order to allow the two engines to rev independently.

From what I've read about this kind of set-up, the driver has the choice of either operating both gearboxes together through a linked gearlever, or he can change gear in just one gearbox or the other - which would obviously mean that the engines would be operating completely out of sync with each other, and yet while still being connected together. As I understand it, being able to mix-and-match the power and torque output of the two engines like this gives better acceleration and performance than if both engines are performing identically (but presumably requires a very skillful driver).

I'm not suggesting that this is remotely relevant to buses (especially as the rpm of a sportsbike engine is 10 times that of a heavy diesel), but just thought I would mention it in passing

Jeremy





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« Reply #18 on: June 10, 2013, 05:03:14 PM »

Reason I ask is that I kinda distinctly remember hearing that kind of mill when riding in a Scenicruser going from Fresno to Bakersfield way back in the summer of 1970.  Four speed.  Kinda slow.  Flat land route running local.

First two gears sounded and felt kinda close, then a gap between second and third and a huge gap between third and fourth.  I asked the driver what the top end was and he told me about 72mph.....after 30 minutes.   HB of CJ (old coot
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« Reply #19 on: June 10, 2013, 05:19:03 PM »

The owner didn't want to spend the money for new pyrometers. 

--Geoff



You are supposed to check the rpm after setting twins,triples or quads when you finish setting with a pyrometer when set right the quads won't vary over 2 rpms between the 4 done that many,many times without problems  
 
Seems like the first shop should have checked the leads and probe Geoff you always replace those on a rebuild according to the DD bible 

One thing I did learn about using a pyrometer on a set of twins you pull the valve covers to be sure both engines have the same injectors only took me 4 hrs to figure out one had 70's and not 60's like the tag said

I did see a 2896 Waukesa destroyed one of three on a drilling rig deck because the driller told a deck hand to check the engines and he didn't know the difference between C and F in degrees a pryometer is a dangerous tool in the wrong hands a great tool if used right    
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Geoff
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« Reply #20 on: June 11, 2013, 10:30:04 AM »

The owner didn't want to spend the money for new pyrometers. 

--Geoff

You must work CHEAP if a second rebuild is cheaper than new pyrometers!  Wink
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« Reply #21 on: June 12, 2013, 08:42:59 AM »

You must work CHEAP if a second rebuild is cheaper than new pyrometers!  Wink
Grin  BK  Grin

The owner was a cheap  bastard.  Anyway, you can set the engines to run the same just using a tachometer if they are set up the same.  Its the speed of the engines that needs to be equal in a twin disc, single output drive.  That way you are putting equal torque on each side.  The pyrometers are helpful but not essential.
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Geoff
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« Reply #22 on: June 12, 2013, 01:06:40 PM »

Have never seen two identical engines, boats, airplanes, nor diesels. Why tweaking one to match the other works good.
Dave M
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