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Rear mounted engine thread?

Discussion in 'The Hokey Ass Message Board' started by oldskoolflyer13, Jul 20, 2011.

  1. RichFox
    Joined: Dec 3, 2006
    Posts: 10,020

    RichFox
    Member Emeritus

    The pivoting sub frame is not uncommon at Bonneville even today. It works for that purpose. But a lot of people think solid mount works as well or better. Looking at results I can only say that there is more than one way to skin a cat. And they all work, when they work. But I don't know of any street driven cars with either. It would be OK cruising the fairgrounds I bet. Hitting the freeway for Memphis, maybe not. Depends on what works for you.
     
  2. oldskoolflyer13
    Joined: Mar 29, 2009
    Posts: 274

    oldskoolflyer13
    Member

    So basically.....connect engine to trans, trans to rear, attach spring....make a hefty teeter totter and figure out the center of gravity and it should all interact like a well orchestrated symphony.

    If stock rear radius rods were modified to make the trailing arm, would they need strengthened....especially if the vehicle was to see street time? Or would something like a gusseted ladder bar be better? All while keeping in mind the over all weight and the fact that it will be running a 4 banger with OHV.

    If the stock radius rod locations are used on a '39 rear.....should the trailing arms remain parallel for as long as possible without creating over a 45 degree bend back to the axle, or bend just aft or forward of the rear engine mounts keeping the angles more like a wishbone? In my head, it would seem more logical to keep them parallel just past the rear engine mounts (as energy travels better in a straight line), then create a transmission mount/support thats a little wider and adjustable to meet the angle of the trailing arms.
     
  3. oldskoolflyer13
    Joined: Mar 29, 2009
    Posts: 274

    oldskoolflyer13
    Member

    Does the weight of wheels and tires also have to be computed when determining the CG?
     
  4. RichFox
    Joined: Dec 3, 2006
    Posts: 10,020

    RichFox
    Member Emeritus

    For it to be a working street driven car I would think (I don't really know) that you need to allow for twist. That is when the right rear tire hits a speed bump that the left one doesn't. Or you hang a high G corner and the body leans. Hard to do with split wishbones. The Bonneville cars that I have seen have a regular little space frame that mounts the engine, trans, and rear end with pivots just ahead of the engine. Springs and shocks from the rear of this to the full frame. It's usually quite narrow to fit in a streamliner and has no provision for the right side to move without the left following. This would promote lots of twisting force if driven in real world situations. I think. Only. Don't know for sure.
     
  5. oldskoolflyer13
    Joined: Mar 29, 2009
    Posts: 274

    oldskoolflyer13
    Member

    Pivoting would be much better than rigid. Its kinda a crap shoot, but Im not afraid to try it....couldnt be any worse than my old '60 Sportster that was on a rigid frame.

    Im sure its been done on the street in a similar application at some point (in the hot rod world). Sometimes the only way is to see what happens.

    It may be a bit of time until this gets going since I leave for southwest asia next month.....but this will be documented in a thread for sure.
     
  6. CutawayAl
    Joined: Aug 3, 2009
    Posts: 2,144

    CutawayAl
    Member
    from MI

    Whether the suspension is a hinge, or if there is no suspension(rigid), the roll center is at ground level, which causes poor handling. Cornering and handling are also unpredictable. Beyond that there are more issues. Ok for Bonneville or drag racing but bad for the street. I am speaking from first hand experience as I once had a light and powerful street car with rigid rear suspension.
     
  7. oldskoolflyer13
    Joined: Mar 29, 2009
    Posts: 274

    oldskoolflyer13
    Member

    I think if its set up similar to split bones or a ladder bar set up, with transverse spring and shocks...that it should accommodate just fine for twisting. May have to play around with the spring and/or shocks and it should handle fine. I havent driven anything with a rear mounted engine like described, but Im sure once the feel for it has been acquired that all should be well.....should being the key word.
     
  8. CutawayAl
    Joined: Aug 3, 2009
    Posts: 2,144

    CutawayAl
    Member
    from MI

    Split wishbones and ladder bars create what is essentially a hinge. The only way that kind of suspension can accomodate roll/twist is for something to bend or flex.
     
  9. Terry Buffum
    Joined: Mar 20, 2008
    Posts: 291

    Terry Buffum
    ALLIANCE MEMBER
    from Oregon

    How did Cotton Werksman build his? It was actually driven, so it might provide a proven model if the idea is a tribute versus a recreation.
     
  10. RichFox
    Joined: Dec 3, 2006
    Posts: 10,020

    RichFox
    Member Emeritus

    I had a 32 front engined coupe with big stiff ladder bars the length of the drive shaft. It was great in a straight line on a smooth course. Put a bump in it and the car was sideways. That's why they have those "floater" kits for when you put ladder bars on Street machines. Allows the rear axle to rotate without twisting the spring. Makes a big difference. Not saying you can't live with a solid rear end. But you will be reminded, often, that it's not a really good solution. IRS is a really good solution. Swing axles or De Dione rear are traditional and better that the pivoting sub frame. Again IMHO for what it's worth.
     

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  11. oldskoolflyer13
    Joined: Mar 29, 2009
    Posts: 274

    oldskoolflyer13
    Member

    The plan is to be able to run it on the street and at Maxton (should it re-open)or alternate location, and maybe a couple times at Bonneville. Im very much into the post WWII days when vets came home and hot rodding/landspeed racing came alive in the U.S. I want to build this, to keep that basic sense of style, early ingenuity, and the willingness to put your balls on the line to drive something like that alive.

    Handling may suck, but whats the difference between the lack of twist on something like this and most traditional rods.....probably not much. Ultimately, its up to the comfort level of the driver to build a machine like this.

    So far the information has been great. Did Cotton Werksman build a MRER? If anyone has pics....please post.
     
    Last edited: Jul 23, 2011
  12. Ned Ludd
    Joined: May 15, 2009
    Posts: 4,263

    Ned Ludd
    Member

    Actually, as there is no roll articulation at all one cannot really talk of a roll centre. It wouldn't be bad at all if it really were at ground level: in fact putting it there takes the rc height out of the equation and increases the effect of anything else one does to change roll stiffness.

    But I agree, this thing needs roll articulation if it is to handle unforeseen bumps etc. at speed and/or see street use. Here's one way. Run something like ifs A-arms either side of the oil pan. The wide-base inner ends pivot on the engine/trans/rear carrier assembly; the ball-jointed outer ends pivot on the car's frame. The A-arms should slope up at about 30°, outer ends up, so as to define an instant centre somewhere between the bottom of the pan and the ground. The ball joints should be about level with the rearmost spark plug, lengthwise. I attach some very rough sketches.
     

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  13. CutawayAl
    Joined: Aug 3, 2009
    Posts: 2,144

    CutawayAl
    Member
    from MI

    If you plot out an axle with no suspension, the ground is where the roll center ends up. Suspension or not, the roll center location is a factor in how the car will behave when cornering.


    ?:confused: You mean like lowering the CG or widening the track width? Those things are a plus regardless of the roll center's height.
     
  14. Ned Ludd
    Joined: May 15, 2009
    Posts: 4,263

    Ned Ludd
    Member

    True enough, especially if you consider that the tyre sidewalls are elastic. If not for that the roll centre would probably be at the outside wheel's contact patch.

    No, I mean changing roll stiffness or, to some extent, changing the cg height of the unsprung mass. Varying the roll axis angle - i.e. the combination of front and rear roll centre heights - influences the proportion of front/rear lateral weight transfer exactly as the combination of front and rear roll stiffness does. But the total amount of lateral weight transfer you've got is finite (barring, as you say, changing cg height or track width), so the greater the proportion of weight transfer acting through the roll centres, the less the remainder that is tuneable with roll stiffness adjustments. That should be obvious if you consider that the roll moment will vary with the height of the cg above the roll axis: but the less roll moment you're working with, the less effect any change in roll stiffness will have.
     
  15. CutawayAl
    Joined: Aug 3, 2009
    Posts: 2,144

    CutawayAl
    Member
    from MI

    Either we aren't communicating very well, or, we have significantly different perceptions of roll center and how it effects vehicle dynamics.:)
     
  16. RichFox
    Joined: Dec 3, 2006
    Posts: 10,020

    RichFox
    Member Emeritus

    I think you both have a differing perception of suspension on rear engine modified roadsters. Think Go Cart. The whole program in building Modified roadsters id aerodynamics within the Ford body shell parameters. It needs to be clean. and fit in the narrow confines of a Ford T body. With the engine and trans using up the same space. Goals are top speed first. Integrity in case of crash second, Appearance third. Cornering fourth on a list of three. Kenze and Leslie used the Ford V8 based swing axle I described before. So did lots of other cars Markley Bros. and also Bob Herda to mention a few. Time to come back to earth on this one.
     
  17. Ned Ludd
    Joined: May 15, 2009
    Posts: 4,263

    Ned Ludd
    Member

    Well, the OP was talking about something streetable :D
     
  18. Terry Buffum
    Joined: Mar 20, 2008
    Posts: 291

    Terry Buffum
    ALLIANCE MEMBER
    from Oregon

    The Werksman roadster was the first of the "drive it to Bonneville, go 200, drive it home" cars. I don't remember if he actually achieved that goal.

    Here is what Google produced - unfortunately, the pictures have left these several year old threads, but perhaps someone can scan the magazines and bring them back.

    Results for Project 200, Cotton Werksman (without quotes):
    ► Search Results


    1. Cotton Werksmans' Ardun-powered T - THE H.A.M.B.

      <button class="vspib"></button><cite>www.jalopyjournal.com &#8250; ... &#8250; Hokey Ass Message Board</cite> - CachedSimilar
      20 posts - 15 authors - Last post: May 4, 2005
      Cotton Werksmans' Ardun-powered T Hokey Ass Message Board. ... I think it was project 200. Made copies of the 3 part buildup, ...
      Ardun guys - piston dome radius qun?&#8206; - 9 posts - Apr 14, 2007
      Cotton Worksman Roadster&#8206; - 20 posts - Apr 9, 2007
      More results from jalopyjournal.com »



      Get more discussion results
    2. hot rod nats 72... - THE H.A.M.B.

      <button class="vspib"></button><cite>66.154.44.164 &#8250; ... &#8250; General Discussion &#8250; Hokey Ass Message Board</cite>
      20 posts - 14 authors - Last post: Apr 23, 2005
      As I recall, it was covered in Rod and Custom as "Project 200 mph. ... Thanks for the pics, Cotton Werksman also built that 200mph rear ...
     
  19. RichFox
    Joined: Dec 3, 2006
    Posts: 10,020

    RichFox
    Member Emeritus

    That is a very slippery term. If it's going to look like Chuck Porters car is has to fit an a very small space with lots of other stuff. DeDeion may be the best answer for a street driven car that actually drives.
     
  20. CutawayAl
    Joined: Aug 3, 2009
    Posts: 2,144

    CutawayAl
    Member
    from MI

    If the goal is a true replica replica, you build an exact clone and live with whatever shortcomings the original car had.If it is a "tribute" car, the idea is to have the look and character of the original car, but not necessarily copy every detail.

    While there are some race cars that can be driven on the street, and there are some street cars it might be possible to race, the two are generally based on different compromises. What is tolerable or even desirable in a race car isn't always the same as what is needed for a reasonable, durable, and safe, street car.
     
  21. Ned Ludd
    Joined: May 15, 2009
    Posts: 4,263

    Ned Ludd
    Member

    Meeting all those conflicting criteria with one simple solution is called genius. It doesn't happen all that often ...
     
  22. dmulally
    Joined: Jul 14, 2010
    Posts: 34

    dmulally
    Member

    Interesting thread. I have something long term on the boil which is a similar setup to what the op is doing.

    In regards to swing axles. Somebody here mentioned camber compensators. Very simple to setup and see's that my rear wheels dont go to negative on rebound. In fact I run a stiff setup and they rarely go anywhere. It is on a circuit racer with close to 300hp pushing through the 36hp VW gearbox. 3rd engine and same gearbox. I just use third and forth gear. First and second are unusable. In regards to suspension on that car I mainly use tyre pressure rather than shock settings and spring rates.

    In regards to your situation I can think of three choices off the top of my head.

    1. Solid mount everything and have a high profile tyre and run it with low pressure to absorb bumps as best as possible and have a springy seat ;-)

    2. Cradle the lot as suggested earlier in this thread. I would also suggest a panhard bar. I would run it pretty soft in the rear also with soft springs and high profile tyres.

    3. Perhaps look at a small gearbox. Look up pictures of the sm420 from a Chev truck. Open centre not torque tube and it is half the length of a typical box. With a saving in length you could run a short tailshaft setup with the rear being four bar or whatever you like.

    Perhaps someone would like to comment more on option three that has had some experience in something similar.
     
  23. RichFox
    Joined: Dec 3, 2006
    Posts: 10,020

    RichFox
    Member Emeritus

    In an early type REMR the cars were pretty much short (100-110 inch) wheel base. Using a 39 Ford transmission there is still no room for a drive shaft of any type. Just a coupling. That's is the reason for this discussion of how to fix the trans output shaft to the differential input. They will likely be coupled. Road going and road racing rear engine cars that I have seen all use IRS, DeDeion, or Swing axles. Common sense would indicate there is a reason for this. Packaging is one important reason for the last two. They don't take up any more room that a standard live axle Ford.
     
  24. oldskoolflyer13
    Joined: Mar 29, 2009
    Posts: 274

    oldskoolflyer13
    Member

    I want to go with what was done back then...I can deal with the short comings and adapt to how the handling is.....we all adapt to different vehicles and there traits through out the span of our life. Ultimately, like back then...its up to the driver. Careful planning, reading SCTA/ECTA rule books, and re-reading the rule books should allow one to have something that looks like a racer from days past, but able to race at today's standards.....I've got over a year till I get back stateside....plenty of time to figure it out.
     
  25. oldskoolflyer13
    Joined: Mar 29, 2009
    Posts: 274

    oldskoolflyer13
    Member

    Can anyone post pictures of period correct setups....like the trailing arms/swing arm?
    Not just the Carrillo Roadster, but others as well....Waite, Brown, and others.

    Even if running the car at ECTA/SCTA events fell through....how many people still build something like this...either replicas, tributes, or just something along those styles? Not many....it may not be popular....but its part of the history. Just like people build belly tankers still......maybe more can start paying homage to MRER's......food for thought
     
    Last edited: Jul 29, 2011
  26. NASTY 1
    Joined: Jul 24, 2011
    Posts: 78

    NASTY 1
    Member

    Here's my 1964 Corvair with a rear engine
     

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  27. Ned Ludd
    Joined: May 15, 2009
    Posts: 4,263

    Ned Ludd
    Member

    Hi Nasty, and welcome. Nice looking Corvair; clean (too clean?) swap. I've always been partial to the early shape.

    Something tells me you haven't read this thread, though! Lots of places your 'Vair will fit right in: try http://www.jalopyjournal.com/forum/showthread.php?t=605714

    Some will say the wheels aren't HAMB-friendly, but they do rather look like late-'60s BMW alloys if you squint really hard ...
     
    Last edited: Jul 30, 2011
  28. I love the Carrillo roadster. I have this blown up and hanging above my desk at work. I'd like to build something like it, but there's nowere to go 178 MPH where I live.
    [​IMG] [​IMG] [​IMG]
     
  29. Ned Ludd
    Joined: May 15, 2009
    Posts: 4,263

    Ned Ludd
    Member

    That is a very sound principle, and one I should recommend always keeping in mind when people summarily declare an overweight, airbag-laden car a "death trap" because it is less overweight and airbag-laden than the model that replaced it.
     
  30. RichFox
    Joined: Dec 3, 2006
    Posts: 10,020

    RichFox
    Member Emeritus

    With the passing of time a lot of new regulations also got passed. I'm not sure about the ECTA but I believe they use the same rules as the SCTA. If so, looking at the cutaway drawing makes it look like a lot of things need to be added in order to run today. As expected, I'm sure. It would be a challenge to fit it all in.
     

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