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Radiator Design - thermal expansion issues

Discussion in 'The Hokey Ass Message Board' started by CharlieLed, Feb 4, 2011.

  1. CharlieLed
    Joined: Feb 21, 2003
    Posts: 2,461

    CharlieLed
    Member

    About a year ago I bought a custom made aluminum radiator. It is a crossflow design with plates welded at the top and bottom of the core which makes the radiator "shell" look like it is all one piece. The manufacturer now tells me that they blew it on this design and that the thermal expansion characteristics of the core do not match those of the shell that surround the core...they say that the core will fail prematurely due to this design defect. I hold a degree in engineering so I understand the concept but I have little experience with how it relates to radiators. Does anyone have firsthand experience with radiator design...if the two tanks are tied together will it cause a problem?
     

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  2. unkledaddy
    Joined: Jul 21, 2006
    Posts: 2,865

    unkledaddy
    Member

    Gee, that's a purty radiator.

    If it's only a year old and the manufacturer admits to blowing it on your design,
    then I would ask for a replacement.
     
  3. CharlieLed
    Joined: Feb 21, 2003
    Posts: 2,461

    CharlieLed
    Member

    Yes, this IS a very purty radiator and the manufacturer has offered to retrofit it for me but their fix will take all the purty right out of it. They want to cut out the top and bottom cross members and remount them to a sliding nut plate that is welded to the ends of the tanks. Now instead of seeing a nice smooth top edge the top will be in three pieces with the center trim section screwed to the new mounting plates. The manufacturer has changed ownership recently and they are trying to fix what the PO had supposedly screwed up.
    Here's a pic of the radiator mounted in the new core support I built for my 56 F100...
     

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  4. 1Bad67
    Joined: Mar 22, 2006
    Posts: 221

    1Bad67
    Member

    Well it certainly makes sence that there would be a problem. The core is gonna get hotter than the end caps, and Aluminum expands a lot. Can't the top cap be made long enough to cover the core and both tanks?
    BTW I doubt they are offering to fix something that aint screwed up.
     

  5. Kevin Lee
    Joined: Nov 12, 2001
    Posts: 7,451

    Kevin Lee
    Super Moderator
    Staff Member

    Given the style of build that seems to be, what about just letting them fix it and fabricating a smoothie cover to hide it?
     
  6. HommerSimpson
    Joined: Jan 16, 2011
    Posts: 29

    HommerSimpson
    Member

    Fab a cover to cover the top thats all purdy ?
     
  7. 53sled
    Joined: Jul 5, 2005
    Posts: 5,818

    53sled
    Member
    from KCMO

    Does aluminum expand that much at 200* ?
    I remember special rulers from shop class that accounted for shrinkage when casting aluminum, but that was a little hotter.
     
  8. unkledaddy
    Joined: Jul 21, 2006
    Posts: 2,865

    unkledaddy
    Member

    Well you can 'run what you brung' until it fails (maybe not) and then take the manufacturer up on his offer to fix it.
     
  9. unkledaddy
    Joined: Jul 21, 2006
    Posts: 2,865

    unkledaddy
    Member

    Found this;
    Aluminum expands around 12 millionths of an inch... per inch... per degree, and steel expands around half that. If we had a cube of aluminum that measured 1" in all 3 directions, it would expand equally with temperature, and would measure about .000012" (twelve millionths of an inch) oversize in all directions if we heated the piece 1 degree F.
     
  10. dave lewis
    Joined: Dec 12, 2006
    Posts: 1,373

    dave lewis
    Member
    from Nampa ID

    I just looked at several aluminum radiators here in the shop. Afco. Howe,Griffin and a northern auto parts top to bottom flow for a 64 1/2 mustang. They all have the top plates fastened to the core ONLY, Or fastened to the core and TACKED to the tank with a very small tack weld...... ( 1/4 " or less )
    My guess would be that someone figured out that welding the header to the tank solid was a bad idea !
    Looks like we learned something today ..VIVA La HAMB !
    Dave
     
  11. CharlieLed
    Joined: Feb 21, 2003
    Posts: 2,461

    CharlieLed
    Member

    The radiator is a 2-pass design, inlet on the top left, outlet on the bottom left. Hottest coolant flows into the top half of the left tank then across the top half of the core to the right tank. From the right tank the coolant flows back acorss the lower half of the core and then out of the radiator. I haven't gotten the engine running yet to test this system but if I were to assume that the hottest the coolant was going to get flowing into the radiator to be around 225 degrees then the core temp would have to vary from 225 at the inlet side to something less at the outlet, let's say 175. That would only be a temperature differential of 50 degrees across the core. If the tanks and the crossmembers were also heated to approximately the same temp as the core, how much temperature differential could there be between the core and the outer tanks/crossmembers? If the metal of the core expands with heat, and the metal of the tanks/crossmembers expand with heat...how much hotter would the core have to be to cause more movement in the core than the framework?
     
  12. Larry T
    Joined: Nov 24, 2004
    Posts: 7,734

    Larry T
    Member

    Just looked at a Griffin and Summit that I have both have 2 tack welds holding the side plates (flipped from yours) to the tanks at each end.
    Surly, all the companies can't be making defective aluminum radiators?
    Can we ask what company you're dealing with? Sounds like they are trying to take care of business.
    Larry T
     
  13. I've seen many OE late model radiators have the top and bottom plates cut to allow expansion. I think your stuck with having them repair yours and having to make it look good yourself. No use in looking good for a few years, only to fail later
     
  14. I guess it depends on what they consider to be premature failure. If normal life expectancy is something like 100000 mile and they find it fails in 50000 then I could live with it. Hard to say what to do.
     
  15. CharlieLed
    Joined: Feb 21, 2003
    Posts: 2,461

    CharlieLed
    Member

    Good info. If the aluminum in the crossmember is .125 and the crossmember is 16 inches long then that could be determined to be 2 cubic inches...making the expansion distance about 24 millionths of an inch. Since the whole radiator is aluminum all of the components will expand at the same rate per unit volume. Given that all parts of this radiator are TIG welded, it seems rather unlikely that movement in the millionths of inches would have an affect. Even without the crossmembers there is the issue of thin cooling tubes mated to a thicker core header mated to a thicker tank...I have never heard of an issue with this configuration so would the length of the cooling tubes change so much more (or less) than the length of the crossmembers to cause a failure? Interesting...
     
  16. harley man
    Joined: Jan 24, 2009
    Posts: 152

    harley man
    Member

    Does not sound right to me.I think your rad is ok.Is the conpany trying to cover something else up?Have over 25 yrs racing alum. rads and have never had this type problem.
     
  17. shmoozo
    Joined: Aug 14, 2007
    Posts: 672

    shmoozo
    Member
    from Media, PA

    I was thinking the same thing.

    He could even make the cover out of polished brass and paint the radiator black and ...

    Okay, maybe that's getting to be a bit much, but the cover idea seems reasonable to me.

    :cool:
     
  18. krusty40
    Joined: Jan 10, 2006
    Posts: 856

    krusty40
    ALLIANCE MEMBER

    My thought is that if the manufacturer thinks it is going to fail then they should refund your purchase; I wouldn't use it even if "repaired" by them, as they evidently don't know how to build a quality radiator. Almost all of the aluminum radiators I have installed in NASCAR Cup cars ( and that numbers in the hundreds) are crossflow with welded top caps; these run at approx. 210* for up to five hours without showing any sign of failure. These radiators are made by the higher $$ suppliers (Ron Davis, C & R, etc). Yours is probably made by a less experienced manufacturer. My guess is that they have experienced leakage problems in the core to tank area and believe that this is the solution, rather than their production method or quality control. vic
     
  19. llonning
    Joined: Nov 17, 2007
    Posts: 680

    llonning
    Member

    Just thinking on the keyboard, and I might be totally wrong about this.

    Could they be thinking about the expansion rate difference between the core thickness and the cross member thickness? They (in theory, anyway) expand and contract at different rates according to the cross section of the material??

    Like I said just thinking.
     
  20. fearnoevo
    Joined: Nov 28, 2009
    Posts: 218

    fearnoevo
    Member
    from Iowa

    It probably has to do with calculated fatigue rates over the life of the radiator through thousands of heating and cooling cycles.

    As mentioned, the actual changes in physical size are small enough to be negligible in a one time deal, but over thousands of cycles, those changes, and their impact on joints, seams, etc, probably add up to significant numbers in their opinion.

    If your business is built around the longevity of your product, anything affecting that, is important to you and your customers.

    I helped design and build a special mold a while back, it had the core half made out of aluminum and the cavity half made from P-20. The aluminum side was chilled with water and P-20 side was heated with oil. We did the math and thought we had sufficient clearance on the guide pins and bushings. The first time the press cycled, the mold locked together, and I got an all expenses eaten trip to Ohio to fix it. After clearancing the bushings, the mold worked fine. The physical size was around 24" x 80" with a 50" shut height. According to the math, the expansion and contraction rates on the two masses was a total range of about .0025". It was enough to cause serious issues.
     
    Last edited: Feb 5, 2011
  21. CharlieLed
    Joined: Feb 21, 2003
    Posts: 2,461

    CharlieLed
    Member

    Thanks for all the inputs guys, I really appreciate it. Some observations that I have made regarding the manufacturer...when I commissioned the build of this radiator it was based on the recommendations of many car builders in SoCal who had used this shop. I went to the shop and toured the manufacturing facility, watched the welders and assemblers build the radiators and fan assemblies. In speaking with the two guys who ran the shop I was convinced that they knew the radiator business and had built hundreds of custom radiator/fan systems for all types of hot rods, customs, and street rods. The counters and walls were covered with photos of high-end cars with their radiators installed. When I took delivery of my setup I was very impressed with the fit and finish, cost was as estimated and schedule was met. I brought the radiator home where it now sits waiting for the completion of my truck.
    Here's where the story gets interesting...last June while at a show in OC I stopped at this manufacturer's booth to talk with the guys from the shop. I was surprised when I was told that they no longer ran the shop and that the "new" management was a guy who had the same last name as that of the shop. This guy looked like he may have been the son of the very original shop owner but whatever the case he came off as a little arrogant and had very little good to say about the guys I had dealt with who built my radiator. Well I had a chance to talk to this guy again at the GNRS and that is when he told me that the way my radiator had been built was not the way he builds them now. He said that he had "learned" from "someone else" that this design was problematic. I have ZERO confidence in this new guy and I am hesitant to have him touch my radiator. As my friends in Texas would say, "all hat and no cattle".
    My next step is going to be to contact Ron Davis and some other well known manufacturers to see if they could shed some light on this matter. I have seen other racing radiators constructed in this manner, Howe for one, so I am thinking that it is not all that unusual. Thanks again for the insights, I will let you know what I find out...
     
  22. krusty40
    Joined: Jan 10, 2006
    Posts: 856

    krusty40
    ALLIANCE MEMBER

    Ron Davis will take care of you, and do it right. vic
     

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