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Redesigned Fuse Block

Discussion in '308/328' started by TurtleFarmer, Apr 5, 2020.

  1. TurtleFarmer

    TurtleFarmer Rookie

    Jan 13, 2020
    28
    Full Name:
    Jason S
    Since I'm sheltered-at-home for the past weeks, it's been a good opportunity to address a few items on the list for the 308. A *very* small silver lining to this COVID mess.

    One of the items on my list was to address the fuse blocks. @Birdman is spot-on about the original fuse blocks being a weak point in the electrical design (of many). His redesign using the Bussman blocks is great, but I'm not a big fan of the AGC glass fuses (altho better than the original European style). The modern blade fuses (ATx) are great from both a convenience and safety perspective.

    So I designed and built a custom PCB. A few features:
    - Uses ATM (mini-blade) fuses
    - Holders for three spare fuses
    - Incorporates multiple FastOn connections for 2 separate loads (same as the original fuse block)
    - Has the fuse size, load description and supply source silkscreen'd onto the board
    - LEDs to indicate fuse status (lit for OK, unlit if blown), actuated by a micro-switch

    It all came out pretty well. It's very solid. I'll be doing a milli-ohmeter check next week to validate the trace resistances, but calc's indicate it should be at least 2-3x better than the original fuse blocks. Pyrometer check under normal load shows no sign of Trise, but I'd like to do a load test sometime in the next couple weeks to validate thermals in a stagnate air box.

    I messed up and ordered bolts that were too short for the center mounts (this is where the ground comes for the LED indicators). So I had to clip test leads on to test out the LEDs...that should be remedied in by early next week (I swear McMaster employs pre-cogs).

    Take a look. Lemme know what you think!
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  2. TurtleFarmer

    TurtleFarmer Rookie

    Jan 13, 2020
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    Jason S
    Oh...and a *huge* shout out to Paul Bennett and the wiring diagrams he provides. They were invaluable in tracking down both the load and supply source names for the silk screen.

    Unfortunately, it also makes me want to redesign the entire wiring harness to avoid long trace runs, ground and supply loops, and add modern connectors/loom. But I think that is best left for the next global pandemic crisis.
     
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  3. Ferraridoc

    Ferraridoc F1 Veteran
    Silver Subscribed Owner

    Jun 20, 2012
    7,276
    Gold Coast, Aust.
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    Patrick
    Looks great, Jason. I built mine out of an aftermarket 10 blade fuse block (x2), that I bridged where necessary with some copper bar. I then got a hold of Sams blocks, which are direct replacements for the OEM ones, but with blade fuses. While you're in the prototype stage, put some lugs on so that the plastic covers can clip on. If I didn't have one already, I'd put my hand up!
     
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  4. pshoejberg

    pshoejberg Formula 3
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    Dec 22, 2007
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    Peter H
    Looks very nice and utilizing proper automotive fuses instead of the glass type seen in other solutions, well done. Do the original plastic covers fit as well?

    Best regards Peter
     
  5. Portofino

    Portofino Karting

    Sep 17, 2011
    211
    Yorkshire UK / Switzerland/ Cote d Azur
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    Portofino
    Excellent....are you gonna start a side job marketing them ?
     
  6. built2grind

    built2grind Karting
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    Oct 16, 2016
    226
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    ANDREW
    Ok, if you go into production with these, I would be interested in replacing mine. These look great for a “prototype” version. Amazing quality job. Well done!
     
  7. JCR

    JCR F1 Veteran
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    Mar 14, 2005
    6,563
    H-Town, Tejas
    Very nice job.
     
  8. st@ven

    st@ven F1 Rookie
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    Aug 4, 2008
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    Steven
    very nice! let me know if yu start a first production run.
     
  9. Dr Tommy Cosgrove

    Dr Tommy Cosgrove Two Time F1 World Champ
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    May 4, 2001
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    Tommy
  10. derekw

    derekw Formula 3

    Sep 7, 2010
    1,080
    London, UK
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    Derek W
    I was going to do this myself but too busy right now designing low cost ventilators so I’d be interested in a set.
     
  11. lm2504me

    lm2504me Formula Junior
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    Aug 26, 2004
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    Nipomo, CA
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    Richard
    Great job!
    Look forward to their production.
     
  12. mexicruiser

    mexicruiser Rookie

    Aug 28, 2012
    44
    That is very nice workmanship! Congratulations, I was evaluating the same project, but you nailed it.
     
  13. TurtleFarmer

    TurtleFarmer Rookie

    Jan 13, 2020
    28
    Full Name:
    Jason S
    Thanks all for the comments and feedback. And nice to hear some there's some interest--I'd started the project just thinking it would a fun exercise for my car (and a good warmup for redesigning the speedometer board).

    I've made a few minor modifications to improve the robustness of the system (add'l blocking diode in the LED path) as well as moved some components around to reduce the likelihood of shorting out during installation and strengthening the mechanical structure of the spare fuse holders.

    The original fuse covers won't fit on this board, but I could certainly design a 3D printed fuse cover. Given the dash location, the inherent safety of the mini ATM fuses, and the dash cover, it's not clear to me that a fuse cover is necessary, but it might clean up the look. There's no economical way to keep the LED lights visible once the cover is on, but you could always remove to check the status. Would love to hear your thoughts on need for a cover....

    I'm considering another run with the minor mods from above. If there's enough interest, I could make that a production assembly of a number of them. This would also require designing and building some tooling to securely and consistently handle the thru-hole component assembly (particularly the FastOn connectors...they are painful).

    My guess is that the final pricing would be in the $300 range (+/-$50), if we had at least 7-8 interested folks.

    Please PM me if interested (not a commitment...just interest). If there's enough interest, I'll start working on a production grade run.

    Thanks again for the feedback and positive comments.
     
  14. GordonC

    GordonC F1 Rookie
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    Aug 28, 2005
    3,634
    Calgary, AB, Canada
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    Gordon
    A long time forum member, Sam Saprunoff, did a limited run of fuse blocks for 308 GT4 and 308 GTB/GTS that uses the mini ATM fuses and takes the factory covers. The covers are nice to have on the blocks because they have the associated circuit labels right on them. I don't believe Sam is doing any more of these blocks, but they are a nice reference for a recent high standard version.

    From Sept 2017: Sam's fuse blocks :) https://www.ferrarichat.com/forum/threads/sams-fuse-blocks-oh-yeah-baby.552934 Oh yeah baby!

    Photos are in post #15. I have a set of these in my 308 QV, and am extremely happy with them.

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  15. Jonny Law

    Jonny Law F1 Rookie
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    May 6, 2008
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    I would be very interested in this design and would be willing to be in the first round. I have a Birdman fuse block which I like very much. Once was stuck of the side of the road with a blown fuel pump fuse. But due to the sunlight hitting the glass was not able to clearly see the break. A LED or even a ATx SmatFuse would clear this problem up.

    Any chance you could add a couple auxiliary always on or ignition on fuse points?
     
  16. Sly_G

    Sly_G Karting

    Mar 5, 2015
    111
    Strasbourg, France
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    Sylvain
    Hey,

    Great work! I would be interested in being in the first run! Count me in!

    Sly
     
  17. built2grind

    built2grind Karting
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    Oct 16, 2016
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    ANDREW
    I’m in, we got 3 now....
     
  18. Steve Magnusson

    Steve Magnusson F1 World Champ
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    Jan 11, 2001
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    Steve Magnusson
    Just curious -- how are you handling that different model 308 fuseblocks do not have the same connections on the backside?
     
  19. TurtleFarmer

    TurtleFarmer Rookie

    Jan 13, 2020
    28
    Full Name:
    Jason S
    @GordonC thanks for pointing out the other ATM design. Looks very clean and nice to have kept the original fuse covers.

    Also, it highlights something I didn't originally think about b/c this was just a project for my vehicle: Ferrari modified the layout, the fuse ratings and the loads across diff't models. My design was very specific to my car (1979 308 GTS) b/c, well, it's the only 308 in my possession :) Thanks to @Steve Magnusson for asking that question--I would not have caught that.

    However, using Paul Bennett's diagrams, I think I should be able to make this generic for all 308 vehicles:
    - All of the fuse rating, supply descriptions and load descriptions will be removed from the silk screen, since it varies from model-to-model. In other words, the board will no longer have descriptors that "conveniently" indicate these things.
    - The Left Side Fuse #3 (L3) supply is sometimes shorted to the Left Side Fuse #1/2 (L1/L2), which is true in my car, and sometimes it's isolated (e.g. 308 GT4, 308 GTxi, QV). This can easily be made a solder "option", so that the same design can support both.
    - The 80's era 308s (GTxi, QV) all seem to utilize dual connections on the supply side of L1 & L2. This should be easily accomplished via a FastOn splitter.
    - Because of the variations in fuse ratings and connections, having a cover that can accept a "sticker" to describe those things would be pretty nice. Will start working on a cover design. I could design it to accept the original stickers (think you can generally get them on EBay) but it'll probably look nicer if I just design new stickers as well. Thoughts?

    Lastly, while I can verify electrical requirements via published wiring diagrams and owners manuals online, it will be impossible for me to verify the mechanical mounting points across all models. I'll need some help from the community to *carefully* get out the calipers and measure the distances between the four mounting fasteners across the various models. Because of the way the fuseboard has been designed, there's some tolerance, but there's a limit. I'll send out the measurements from my car later today. And again....be very very careful in measuring. The fuses are hot (12V), and the mounting plate is live (GND)--you will destroy a nice set of calipers if you're not careful.
     
  20. Steve Magnusson

    Steve Magnusson F1 World Champ
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    Jan 11, 2001
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    Steve Magnusson
    Pretty sure that the mounting hole spacing and general geometry of the blocks is something that is common on all the 308 fuseblocks -- Ferrari just changed the pattern of riveted plates on the backside as different models and/or versions required.
     
  21. johnny308

    johnny308 Karting
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    Dec 3, 2011
    129
    Greenfield, MA. USA
    I would like a set !!
     
  22. Glassman

    Glassman F1 World Champ
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    Apr 23, 2002
    13,009
    I've yet to find a decent workable replacement fuse block. I plan on repairing mine and be done with it.
     
  23. Patrick Dixon

    Patrick Dixon Formula Junior

    Mar 27, 2012
    675
    UK
    I have Sam's ones too and they are pretty much perfect. Sam is also a pleasure to deal with. It's a shame he's not doing any more, although I understand it's a lot of hassle for not much reward!
     
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  24. TurtleFarmer

    TurtleFarmer Rookie

    Jan 13, 2020
    28
    Full Name:
    Jason S
    Update: We're up to six folks who've raised their hands in interest--would love a couple more to make this make sense.

    Also, I've been working thru the list of ECOs. In particular, I wasn't happy about supporting the 80's era 308's using a FastOn splitter (see my note above). This was one of the *main* design goals of this project--no splitters. In the world of electrical design, the vast majority of failures occur at connections--using a splitter adds an additional connection point in the electrical path which increases the resistance and, hence, the likelihood of failure. Doing this at the fuse box (primary distribution point of the entire electrical system) really makes me crazy uncomfortable.

    Here's what a splitter looks like, btw:
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    So I've designed the board to have "stuffing" options, which should allow it to support all generations of 308s. In the 78-79 308's, the "supply" side connectors just had single connections, but in the 80's era 308's, the left most two fuses (L1 & L2 in my nomenclature) each had two supply side connections. So to support those vehicles the new design allows for optional supply side connections on the bottom side for L1 & L2. You can see this in the quick CAD screenshot of the bottom side of the design. Circled in blue are two add'l connectors that match the two add'l connectors riveted into the original Ferrari design. This will provide much better connectivity than either the original design or by using a splitter with lower likelihood of failure.
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    (Circled in red you can also see the optional shorting block used to support those models that had L3 connected to the L1/L2 supply.)

    I'm mostly thru designing the tooling for ease of assembly and designing a cover is next up.
     

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