1. Registration trouble? Please use the "Contact Us" link at the bottom right corner of the page and your issue will be resolved.
    Dismiss Notice

Flat fender frame clone

Discussion in 'Flat Fender Tech' started by oldtime, Jul 12, 2015.

  1. Jul 12, 2015
    oldtime

    oldtime oldtime

    St. Charles,...
    Joined:
    Aug 14, 2006
    Messages:
    3,466
    Considering monting a flatty tub onto a cloned CJ frame.
    Using a 80" wheelbase frame at rear which has typical 42" leaf springs.
    Splice that to a an early CJ-5 front frame to get longer 39-5/8" front leaf springs.

    Any one been there ?

    Could use an ECJ-5 measurement.
    What's the stock distance between front and rear spring pivot bolt brackets.
    Bolt CL to bolt CL ?
     
  2. Jul 13, 2015
    mullen46cj2a

    mullen46cj2a Member

    Harrisville, WV
    Joined:
    Apr 11, 2006
    Messages:
    71
    Oldtime - I have both frames available that I can get any measurements you need. I have a '55 CJ5 frame - will the dimensions from it suffice?





     
  3. Jul 13, 2015
    oldtime

    oldtime oldtime

    St. Charles,...
    Joined:
    Aug 14, 2006
    Messages:
    3,466
    I happen to have an 80" frame with good rear and mid section.
    The front of the frame is missing just foreward of the front pivot brackets.
    I intend to use a CJ-3 tub for the build so the rear frame section is good to go.
    I can readily find CJ-5 donor frames and would not mind having the slightly longer front leaf anyway.

    My CJ-3 frames measure 41-1/8" between the spring pivot brackets.
    Just wondering what the CJ-5 frames measure in that stretch.
    That will tell me how much the wheelbase is effected.
    I don't believe a 1955 CJ5 frame will suffice for measurements because it has reversed front shackles.
     
  4. Jul 13, 2015
    Warloch

    Warloch Did you say Flattie??? Staff Member

    Falcon, CO
    Joined:
    Mar 4, 2003
    Messages:
    5,466
    I have the '63 frame under a '49 body in the shop. I can get that for you tomorrow. On the other hand - the Frame for a V6 unit (FSM) shows 38 13/32 CL to CL on the front spring mounts. Rear are 44 25/32.
     
  5. Jul 14, 2015
    oldtime

    oldtime oldtime

    St. Charles,...
    Joined:
    Aug 14, 2006
    Messages:
    3,466
    I was wondering what's the CJ-5 distance between the spring pivot brackets. (not including any of the shackle brackets)
    From that I can figure the exact wheel base change.

    What I'm mainly looking to gain are the longer front leaf springs.
    Ideally I would probably want to install 42" leafs at both front and rear.
    But doing that would probably require a totally custom built frame.

    My rear frame section is already ideal for the 3A tub with 42" leafs.
    Standard 3A front springs are only 36-1/4" long.
    So what I hope to do is splice on a CJ-5 front frame section to get the longer 39-5/8 long front springs.

    One good thing is that I can splice the frames together just ahead of the front spring pivots and just behind the engine brackets. That section appears to be the strongest area of the frame.
    In fact I think I can splice it without adding gussets so it could appear to be a factory built frame.
    Diagonal splice the frame channel in one direction and diagonal splice the inner stiffener in another direction.

    Chuck I'm curious.
    How did you get the CJ5 rear frame crossmember to fit up under the CJ-3A tub ?
     
    Last edited: Jul 14, 2015
  6. Jul 15, 2015
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
    Joined:
    Sep 21, 2002
    Messages:
    12,367
    I'll add myself to the list of trying to get the measurement for you tomorrow. Of all of the measurements in the FSM that one isn't there.
     
  7. Jul 15, 2015
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
    Joined:
    Sep 21, 2002
    Messages:
    12,367
    The CJ5 frame measures 38 1/4" between those 2 points. To verify what you want I measured my 3B and match your measurement. Unless I don't understand what you are looking to figure out won't the measurement be irrelevant anyway? Since you have the spring hanger/pivot point on the original frame then using the original length springs would leave your wheel base original. Taking half of the difference in length of the longer springs will give you the difference in wheel base change/addition. At least that's the way I see it. ;)
     
  8. Jul 15, 2015
    Warloch

    Warloch Did you say Flattie??? Staff Member

    Falcon, CO
    Joined:
    Mar 4, 2003
    Messages:
    5,466
    Sorry Oldtime - work got the best of me.

    It may have to do with the mods I did to fit the rear tank on, or the body lift with the new body mounts (to fit the 225 easier) - I'll look and let you know as my memory is a bit fuzzy there.
     
  9. Jul 17, 2015
    Warloch

    Warloch Did you say Flattie??? Staff Member

    Falcon, CO
    Joined:
    Mar 4, 2003
    Messages:
    5,466
    Yup - rear tank and body lift fixed that for me this time. I do remember moving and augmenting that cross member on ones in the past without the rear tank.
     
  10. Jul 18, 2015
    oldtime

    oldtime oldtime

    St. Charles,...
    Joined:
    Aug 14, 2006
    Messages:
    3,466
    Thanks Glenn.
    The front flatfender springs are 36-1/4" long.
    The front CJ-5 / 6 springs are 39-5/8" long.

    I would gain 1/2 that difference in wheelbase.
    1/2 that difference is 1-11/16".

    I would gain almost 1-3/4" wheelbase up front if I leave the spring pivot distance at 41-1/8".
    1-3/4" wheelbase increase may be a tad much ?
    It would put the front tire foreward in the front fender and I don't want the tires way out of proportion to the front fenders.

    May need to splice frame right behind the front spring pivot bracket to set the distance at 41-1/8" minus 1-11/16".
    In other words set the distance between spring pivots to 39-7/16" and that should retain the standard 80" wheelbase.

    Chuck.
    Considering the tub fitment issues I just don't see a huge advantage in using the CJ-5 rear springs.
    The front CJ springs are always much shorter than the rear leafs.
    If anything the front spring length needs to match the rear length.
    In my mind there is little reason to lengthen the rears until after the front springs have equaled the rears in length.

    So my basic goal here is to work toward longer front springs on a flatty.
    If I was to go so far as to mount 42" rear springs up front then I would also consider doing a completely custom frame.

    I'm sure that the off center mounted Holbrooks work well but I still like the idea of springs being mounted at mid leaf.
    I prefer the idea of a universal (versatile) CJ over that of an offroad crawler.
    I suspect Holbrooks are a bit swayish on the road.
    The only practical remedy to Holbrook body sway would be the adjustable shocks.
    Do the RS 9000 series fix the body sway during high speed cornering ?
     
  11. Jul 18, 2015
    Warloch

    Warloch Did you say Flattie??? Staff Member

    Falcon, CO
    Joined:
    Mar 4, 2003
    Messages:
    5,466
    The Holbrooks do make the ride MUCH smoother in all situations - even compared to a rig with Skyjacker soft rides. The RS 9000s do give you the ability to take the sway out at higher speeds, and still retain much of the ride quality.
     
  12. Jul 19, 2015
    tarry99

    tarry99 Member

    Northern California
    Joined:
    Oct 29, 2012
    Messages:
    3,784
    The Holbrooks are pretty flexy and do improve the ride both on and off the trail , but on the pavement going around turns will make most folks pucker up a little.........I personally like a sway bar up front with disconnects..........calms the roll down while on the road with no additional shock adjustment needed.

    A Combination of both Bar & shock is where I was going with my old CJ-5 chassis prior to it's sale.
     
  13. Jul 20, 2015
    cadwelder

    cadwelder Member

    Milton KY
    Joined:
    Jun 2, 2011
    Messages:
    202

    Ken:

    I have both a 3A and an ECJ5 ('69 V6) frames and have compared them for differences and similarities. As a reference for horizontal (X-axis) measurements I used the forward Ross steering box mounting hole in the frame. What I've found is as follows:

    Both frame rails are identical as far as overall shape/contour/profile. 2.5" of length were added to the front of the CJ5's frame, and 3" of length were added to the back (additional lengths were added at shackle mount areas); shackle mounts are the same distances from the ends of the frames on both frames. The 5's body mounts are in the same spot as those on the 3. The rivet holes for the F-head motor mounts are the same distance from the reference holes on both frames.

    Spring pivot mounts have different placements between the two frames: front spring pivot mount hole on the CJ3 is exactly in line (horizontally) with steering box reference hole, while on the 5 it was moved aft exactly 1" for longer springs. The rear spring center was moved forward on the 5, but I do not have the exact distance at this time (can obtain later if needed).

    Having stated all that, if you spliced the frames forward of the front spring center and do not move the spring center back 1", your wheelbase will be 1" longer than that of an early CJ5, or 82". I am thinking it might be better/easier to layout and cut at a point 6" or 8" behind the forward steering box mount on both frames and splice it there.
     
    Last edited: Jul 21, 2015
  14. Jul 21, 2015
    oldtime

    oldtime oldtime

    St. Charles,...
    Joined:
    Aug 14, 2006
    Messages:
    3,466
    Yeah Dennis, I follow what your saying.
    The exact wheelbase is 1/2 the front spring length plus 1/2 the rear spring length plus the distance between spring pivot brackets.
    CJ-2A, CJ-3A, DJ-3A and CJ-3B = 36-1/4 front spring and 42 " rear spring with 41-1/8" between pivots
    CJ-5 = 39-5/8 front spring and 46" rear spring with 38-1/4" between pivots

    Flattys = 18-1/8" + 21" + 41-1/8" = 80-1/4" WHEELBASE
    CJ-5 = 19-13/16" + 23" + 38-1/4" = 81-1/16" WHEELBASE
    Spliced frame CJ-5 front with CJ-3 rear = 19-13/16" + 39-7/16" + 21 = the original 80-1/4" WHEELBASE

    I would not change the distances between spring pivots and the shackle brackets.
    I could change the distance between the spring pivot brackets as required.
    That would effect the placement of the front wheels inside the front fenders.
    If I go with 39-7/16" between spring pivots that will keep my wheelbase at 80-1/4"
     
    Last edited: Jul 21, 2015
  15. Jul 21, 2015
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
    Joined:
    Sep 21, 2002
    Messages:
    12,367
    It's probably part of your plan already, but if I were you I would get the CJ5 frame before you do any cutting so you can do a thorough comparison. :)
     
  16. Jul 22, 2015
    oldtime

    oldtime oldtime

    St. Charles,...
    Joined:
    Aug 14, 2006
    Messages:
    3,466
    Yeah Glenn, I certainly agree.
    I actually have 2 other builds to complete before I get to this idea.
    I just like to think way out ahead for distant future projects.
    Anymore I never even start a project before its mentally assembled and is complete in all detail.
     
  17. Jul 22, 2015
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
    Joined:
    Sep 21, 2002
    Messages:
    12,367
    Anymore I never start a project until I'm sure I'm mentally able......period! ;)
     
New Posts