PRV as stressed member
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  1. #1
    Tadpole
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    Default PRV as stressed member

    My hillclimb car uses a PRV engine as a stressed member, carrying gearbox/ rear suspension. It leaks oil
    right rear of joint between block and lower crankcase. Has anyone any experience of this.

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  2. #2
    Budding Architect ???? pugrambo's Avatar
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    Quote Originally Posted by renaultracer View Post
    My hillclimb car uses a PRV engine as a stressed member, carrying gearbox/ rear suspension. It leaks oil
    right rear of joint between block and lower crankcase. Has anyone any experience of this.
    yes

    pull the lower crankcase off and ensure both surfaces are in perfect condition and if so reseal with a jointing paste but i think you will find you have a crack there as this is also where the gearbox bolts up to
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  3. #3
    Tadpole
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    Default PRV as stressed member

    Thanks Pugrambo,
    I have done all that (no cracks), my problem is more of a torsional nature, I was hoping someone may have had experience of the ability of the block to cope with the torsional load from rear suspension.

  4. #4
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    Quote Originally Posted by renaultracer View Post
    My hillclimb car uses a PRV engine as a stressed member, carrying gearbox/ rear suspension. It leaks oil
    right rear of joint between block and lower crankcase. Has anyone any experience of this.
    hmm! it seems that it is not just a stressed but a strained member. rethink things?
    peter

  5. #5
    1000+ Posts geckoeng's Avatar
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    Default Stressed Motor !!!

    Which motor is it ??

    Ali V6 would not be able to be used as a stressed member. All the ali motors I have seen in race cars have a steel frame cast in the blocks, or specific reinforcing ribs to carry the load.

    Cast 4 cyl should be able to take it, as Formula Renault and FF2000 are stressed motor.
    Ray geckoeng

    Think Old, But Run Modern !!

  6. #6
    Tadpole
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    Default PRV as stressed member

    Thanks Peter,
    I have a 35mm sump cast from AP601 heat treated T6 with 4xM12 holes front and back, a cradle that
    bolts to chassis, engine mounts, sump and rocker covers. The gearbox adaptor bolts to sump and engine.
    I had hoped this would be enough, but the leak recurs behind engine mount, so as you say strain is occurring in in this unsupported zone. I am currently fabricating struts to go from engine mount to top wishbone pickup bracket on gearbox adaptor. I am not sure this will adequately isolate torsional effect from engine, but it would be extremely difficult to fit a full tubular chassis in this area.
    I have found the leaking area of flange has two redundant holes in block face, one 18mm dia the other 10mm dia. that reduce the surface area for sealing. These will be filled with Devcon and flushed off.
    If block is flexing I guess it wont be long before liners leak.
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  7. #7
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    Quote Originally Posted by renaultracer View Post
    If block is flexing I guess it wont be long before liners leak.
    You could partially grout the block to make it stiffer and seal the liners.

    Maybe an inch above the liner seals to ensure it doesn't run hot.

    There are a few proprietary resin grouts used in Drag cars.

    The only problem is, that you'd have to throw the block away if you damage a liner as once the stuff cures, it has cured for good.

  8. #8
    Tadpole
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    Default PRV as stressed member

    Thanks Geckoeng, Motor is B27.

  9. #9
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    Quote Originally Posted by renaultracer View Post
    Thanks Peter,
    I have a 35mm sump cast from AP601 heat treated T6 with 4xM12 holes front and back, a cradle that
    bolts to chassis, engine mounts, sump and rocker covers. The gearbox adaptor bolts to sump and engine.
    I had hoped this would be enough, but the leak recurs behind engine mount, so as you say strain is occurring in in this unsupported zone. I am currently fabricating struts to go from engine mount to top wishbone pickup bracket on gearbox adaptor. I am not sure this will adequately isolate torsional effect from engine, but it would be extremely difficult to fit a full tubular chassis in this area.
    I have found the leaking area of flange has two redundant holes in block face, one 18mm dia the other 10mm dia. that reduce the surface area for sealing. These will be filled with Devcon and flushed off.
    If block is flexing I guess it wont be long before liners leak.
    My only thought as a possible fiddle is to find more places on the motor to get mounts from block to frame happening. That is, spread the stress loads more. Peter

  10. #10
    Fellow Frogger! Ross's Avatar
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    Cool car, can you give us some details, engine mods, etc
    Ross:

    1989 Alpine GTA Twin Turbo
    1963 Renault R8
    1996 Peugeot 106 S16
    1967 NSU Prinz 1200TT
    1989 Peugeot 205 GTi

  11. #11
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    Default PRV as stressed member

    Ross, love your dauphine, often thought one of those would go well with my motor in the back seat.
    My car has a standard balanced motor in it at present, to get it and me sorted. I have good motor to assemble with forged pistons, SS valves, beaut porting job, etc. Flywheel is light alloy, Tilton triple plate clutch, gearbox is Hewland FGC with 23 ratios to choose from

  12. #12
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    Default PRV as stressed member

    Ross, love your dauphine, often thought one of those would go well with my motor in the back seat.
    My car has a standard balanced motor in it at present, to get it and me sorted. I have good motor to assemble with forged pistons, SS valves, beaut porting job, etc. Flywheel is light alloy, Tilton triple plate clutch, gearbox is Hewland FGC with 23 ratios to choose from. Turbo,wastegate and intercooler as you can see in the images attached.
    Should be a lot of fun when I get this oil leak sorted.
    Geoff.

  13. #13
    Fellow Frogger! Ross's Avatar
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    So when you say standard motor is that a standard turbo motor?
    Images didnt come through for some reason.
    Ross:

    1989 Alpine GTA Twin Turbo
    1963 Renault R8
    1996 Peugeot 106 S16
    1967 NSU Prinz 1200TT
    1989 Peugeot 205 GTi

  14. #14
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    Default PRV as stressed member

    Yes Turbo motor.
    Attached Thumbnails Attached Thumbnails PRV as stressed member-img_3270.jpg   PRV as stressed member-img_3211.jpg   PRV as stressed member-race-car-1.jpg  

  15. #15
    Member ScottR's Avatar
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    Quote Originally Posted by renaultracer View Post
    Thanks Peter,
    I have a 35mm sump cast from AP601 heat treated T6 with 4xM12 holes front and back, a cradle that
    bolts to chassis, engine mounts, sump and rocker covers. The gearbox adaptor bolts to sump and engine.
    I had hoped this would be enough, but the leak recurs behind engine mount, so as you say strain is occurring in in this unsupported zone. I am currently fabricating struts to go from engine mount to top wishbone pickup bracket on gearbox adaptor. I am not sure this will adequately isolate torsional effect from engine, but it would be extremely difficult to fit a full tubular chassis in this area.
    I have found the leaking area of flange has two redundant holes in block face, one 18mm dia the other 10mm dia. that reduce the surface area for sealing. These will be filled with Devcon and flushed off.
    If block is flexing I guess it wont be long before liners leak.

    When you say torsional load, do you mean parallel to the crank shaft, or parallel to the rear axle ?

    and is the likely cause from, acceleration torque, braking torque (from rear wishbone mounts), or from torsional chassis flex ?

    If the leak is at lower crankcase, perhaps the sump (being attached to the gearbox / cradle etc) is transferring too much force to the lower crankcase ??

    Good luck, hope you get it sorted without too much redesign, looks like a little weapon !

    Regards
    Scott

  16. #16
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    Quote Originally Posted by ScottR View Post
    When you say torsional load, do you mean parallel to the crank shaft, or parallel to the rear axle ?
    It's hard to be sure based on the photo, but I can't see any chassis whatsoever rear of the drivers cockpit.

    It looks as though the engine supports the entire back half of the car and the suspension is mounted to the gearbox (which is supported by the engine).

    It looks like the engine is attached to the chassis at the top (the metal brackets on the cam covers) and the bottom (around the crankcase)

    If all that is the case, I think the block is under far too much stress.

    One possible solution would be to make a triangulated link from about halfway up the roll over hoop (opposite the cross brace) going back to the the gearbox end of the engine where you could make up mounting plates to attach to the cam covers in a similar fashion as has been done at the front.

    This would mean the engine is mounted both front and back and would reduce the torsional loads on the block greatly.

    You might be able to package it all in without to much problem.

    Something like this -



    Obviously triangulating to something further back would be better still (maybe a solid bracket welded to the bellhousing and a single two armed engine support linked by webbing behind the engine?), but that may not be feasible without re-configuring half the car.

    Bit hard to visualise the height of the heads but maybe something like this with a cross webbing (with speed holes) going to a similar bar on the other side.

    You could unbolt from the chassis/bellhousing it to remove the engine or gearbox


  17. #17
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    Quote Originally Posted by mistareno View Post
    It's hard to be sure based on the photo, but I can't see any chassis whatsoever rear of the drivers cockpit.

    It looks as though the engine supports the entire back half of the car and the suspension is mounted to the gearbox (which is supported by the engine).

    It looks like the engine is attached to the chassis at the top (the metal brackets on the cam covers) and the bottom (around the crankcase)

    If all that is the case, I think the block is under far too much stress.

    One possible solution would be to make a triangulated link from about halfway up the roll over hoop (opposite the cross brace) going back to the the gearbox end of the engine where you could make up mounting plates to attach to the cam covers in a similar fashion as has been done at the front.

    This would mean the engine is mounted both front and back and would reduce the torsional loads on the block greatly.

    You might be able to package it all in without to much problem.

    Something like this -



    Obviously triangulating to something further back would be better still (maybe a solid bracket welded to the bellhousing and a single two armed engine support linked by webbing behind the engine?), but that may not be feasible without re-configuring half the car.

    Bit hard to visualise the height of the heads but maybe something like this with a cross webbing (with speed holes) going to a similar bar on the other side.

    You could unbolt from the chassis/bellhousing it to remove the engine or gearbox

    yep; i agree that stress spreading is the path forward peter

  18. #18
    Tadpole
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    Thanks to all that offered advice on this subject. A subframe tube chassis was constructed and all stress removed from block. Had first event last weekend and all went well ( except for gear change, thats the next job)

  19. #19
    Fellow Frogger!
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    If that is the car parked next to us at Kempsey i pointed out a pool of oil on the ground to the fellow with the hat after you had gone to the start,his reply was did not want to see that".

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