Sab-a-dab-a-doo! The back-country LJ build has officially started
- Thread starter sab
- Start date
I can think of a few fat Jeep pigs that still fit with that methodology
As can I think of quite a few fat jeeps that got that way slowly
Even though you haven't seen a post from me so far this weekend, don't think I was slackin'! I spent all weekend designing the cutting brake lever installation in the cab and the plumbing. My inspiration for installing cutting brakes came from reading @B00mb00m's build thread a few years ago and trading PMs with him. After researching options for the master cylinder/lever assembly, I ended up purchasing the Jamar JUS2002X dual lever setup:
B00mB00m ended up modifying his levers so that he pushes, instead of pulls, the levers to activate the brakes. I decided to keep it a pull system since I'm used to using a parking brake to slide the rear of a car around a corner, and that works well for me. The only space on the floor between the seats left for the levers is, like B00mB00m's installation, inside the center console. However, my LJ came with the subwoofer there, so I'm going to lose it. I'm not much of an audiophile, but I have played the radio with the subwoofer disconnected (by accident), and the sound is horrible. I guess I'll buy and install a powered sub to mount under one of the seats before I reinstall them. But that's for another day...
The first order of business was to determine how to plumb the system. It's a pass-through device. The center port is input pressure from the brake pedal via the combination block, and the two outside ports are output pressures to the respective rear brake calipers. When the brake pedal is pushed, pressure moves through the Jamar cylinders to both calipers, and when the levers are pulled, pressure moves only from that cylinder to the respective caliper. So, I need to plumb from the combination block to the Jamar center port, and then from each master cylinder output port to a rear caliper.
Since the input line will be completely attached to the body, it'll all be hard line. For each of the output lines, there'll be a hard line from the master cylinder, through the floor of the tub, and to a bulkhead fitting mounted to the bottom of the tub on the side of the body, just inside of, and above, the frame. Then there will be a flex hose from that bulkhead fitting to a second bulkhead fitting on the new mid-arm control arm mounts. From there, another flex hose will run down the control arm to the rear axle.
I haven't completely figured out the rear axle plumbing, yet, but it'll start with a bulkhead fitting in the center, run through rigid tubing the outside, and then transition to a short hose to the caliper (thanks to @mrblaine!) I know there's a lot to take in with this paragraph, so hopefully this hastily-drawn schematic might help understand the complexities of this plumbing:
The next thing to do was to decide where to mount the assembly on the floor. I wanted it as far forward inside the console as possible to retain as much storage in the console as I can. As you know, every bit of space in a TJ is precious! To figure that out, I set the assembly next to the console and looked from the side to line up the levers with the rear cupholder. I wanted the levers to come out of the console just above the cupholder. That position turned out to be about 8-5/8" between the centerline of the two rear mounting holes on the Jamar bracket and the centerline of the two mounting holes in the rear cupholders of the center console. That gave me a reference on the tub floor to work with.
Looking at the inside floor and the underside of the tub floor, I found a good place to mount the bulkhead fittings in the floor and drilled three holes for them. Here's what it looks like (imagine hard lines running from the Jamar assembly to the bulkhead fittings):
I designed a 7075 aluminum mounting plate for the underside of the tube below the Jamar assembly in Fusion and have SendCutSend making it for me:
I'll tap those holes for Heli-coils and use it without nuts, for simplicity. I have plenty of flathead 5/16-18 screws for that.
Next, I realized that the Jamar handles being straight is going to make them awkward to pull due to the console being right behind them. So, going back to Fusion, I designed a replacement lever with a bend in it. I also saved a pound for the two levers by having SendCutSend make them out of 7075 aluminum instead of the steel of the original design! Here's the new lever:
And here's a mock-up at rest:
And pulled back:
To prevent the pivot holes from wallowing over time, I sourced a bronze bushing to press into the holes, and I will be replacing the button head cap screws used for the original pivot bolts and replace them with shoulder screws:
The bulkhead fittings I'm using are -3AN, both straight and elbows:
I couldn't find a mounting tab for these, so, once again, I went back to Fusion, designed one up, and sent it to SendCutSend:
I expect most of my parts will arrive by the end of the week, but the SendCutSend parts may not. We'll see what I can accomplish next weekend. Stay tuned...
B00mB00m ended up modifying his levers so that he pushes, instead of pulls, the levers to activate the brakes. I decided to keep it a pull system since I'm used to using a parking brake to slide the rear of a car around a corner, and that works well for me. The only space on the floor between the seats left for the levers is, like B00mB00m's installation, inside the center console. However, my LJ came with the subwoofer there, so I'm going to lose it. I'm not much of an audiophile, but I have played the radio with the subwoofer disconnected (by accident), and the sound is horrible. I guess I'll buy and install a powered sub to mount under one of the seats before I reinstall them. But that's for another day...
The first order of business was to determine how to plumb the system. It's a pass-through device. The center port is input pressure from the brake pedal via the combination block, and the two outside ports are output pressures to the respective rear brake calipers. When the brake pedal is pushed, pressure moves through the Jamar cylinders to both calipers, and when the levers are pulled, pressure moves only from that cylinder to the respective caliper. So, I need to plumb from the combination block to the Jamar center port, and then from each master cylinder output port to a rear caliper.
Since the input line will be completely attached to the body, it'll all be hard line. For each of the output lines, there'll be a hard line from the master cylinder, through the floor of the tub, and to a bulkhead fitting mounted to the bottom of the tub on the side of the body, just inside of, and above, the frame. Then there will be a flex hose from that bulkhead fitting to a second bulkhead fitting on the new mid-arm control arm mounts. From there, another flex hose will run down the control arm to the rear axle.
I haven't completely figured out the rear axle plumbing, yet, but it'll start with a bulkhead fitting in the center, run through rigid tubing the outside, and then transition to a short hose to the caliper (thanks to @mrblaine!) I know there's a lot to take in with this paragraph, so hopefully this hastily-drawn schematic might help understand the complexities of this plumbing:
The next thing to do was to decide where to mount the assembly on the floor. I wanted it as far forward inside the console as possible to retain as much storage in the console as I can. As you know, every bit of space in a TJ is precious! To figure that out, I set the assembly next to the console and looked from the side to line up the levers with the rear cupholder. I wanted the levers to come out of the console just above the cupholder. That position turned out to be about 8-5/8" between the centerline of the two rear mounting holes on the Jamar bracket and the centerline of the two mounting holes in the rear cupholders of the center console. That gave me a reference on the tub floor to work with.
Looking at the inside floor and the underside of the tub floor, I found a good place to mount the bulkhead fittings in the floor and drilled three holes for them. Here's what it looks like (imagine hard lines running from the Jamar assembly to the bulkhead fittings):
I designed a 7075 aluminum mounting plate for the underside of the tube below the Jamar assembly in Fusion and have SendCutSend making it for me:
I'll tap those holes for Heli-coils and use it without nuts, for simplicity. I have plenty of flathead 5/16-18 screws for that.
Next, I realized that the Jamar handles being straight is going to make them awkward to pull due to the console being right behind them. So, going back to Fusion, I designed a replacement lever with a bend in it. I also saved a pound for the two levers by having SendCutSend make them out of 7075 aluminum instead of the steel of the original design! Here's the new lever:
And here's a mock-up at rest:
And pulled back:
To prevent the pivot holes from wallowing over time, I sourced a bronze bushing to press into the holes, and I will be replacing the button head cap screws used for the original pivot bolts and replace them with shoulder screws:
The bulkhead fittings I'm using are -3AN, both straight and elbows:
I couldn't find a mounting tab for these, so, once again, I went back to Fusion, designed one up, and sent it to SendCutSend:
I expect most of my parts will arrive by the end of the week, but the SendCutSend parts may not. We'll see what I can accomplish next weekend. Stay tuned...
That’s cool, Scott. I’m unclear on something though: You mentioned the valve is pass through. Does the cutting valve create pressure to actuate the brake caliper, or does the pressure still come from the MC? My read of the description makes it seem like the valve interrupts the pressure to the opposite brake caliper.
I may be reading this incorrectly - it’s early…
I may be reading this incorrectly - it’s early…
B00mb00m
The Church of Cutting Brakes of Atlas-Front Digs
Supporting Member
Ride of the Month Winner
Stoked to see someone do this and improve on my hack job!
B00mb00m
The Church of Cutting Brakes of Atlas-Front Digs
Supporting Member
Ride of the Month Winner
I think you did a fine job with yours!
Thank you, but it ain't done, yet...
Yes, each of those levers actuates a piston to generate pressure to the respective rear caliper. I don't know how the internals work to prevent the pressure generated by the lever from going back to the master cylinder at the firewall. I suspect it's done by port location - once the cutting brake piston moves a little bit, the piston moves past the port that goes to the firewall master cylinder. A check valve wouldn't work because there would be no way for fluid to flow back to the firewall master cylinder. If I ever disassemble that Jamar cylinder, I intend to investigate.
I think this is how they work , I've used Jamar on a Baja bug and a class 1/2 1600 , they work great on that weight vehicle. I don't doubt they will be good on a Jeep also. Nice build man.
That's very cool. I run a split parking brake on mine which acts as a cutting brake, but with the pressure of, well, a parking brake. It works, but this is a much more elegant solution. I may look into doing this when I finally get around to building a new console.
May have missed it, but do you have a link for the Jamar?
No, I've not been linking to product links because they die over time. Here it is on the Jamar site:
https://jamarperformanceusa.com/collections/featured-products/products/jus2002x
Many places sell them. I think I bought mine here on sale:
https://dunebuggywarehouse.com/products/jamar-dual-cutting-brake-jus2002x
That is how a normal master works, the piston moves past the port from the reservoir that fills the master bore. But, the cutting brake master has to deal with fluid volume and it may be as simple as it letting it fill behind the piston as it moves and upon retraction, just pushes that fluid back into the vehicle master/reservoir. The firewall master does it that way, there is fluid on both sides of both pistons.
Thanks for that tidbit. I did a lot of engineering on vehicles over the years, but never brakes (or hydraulic clutches), and I've never disassembled master or slave cylinders over all these years to see how they work! I had my ideas, but they were just that - ideas...
I look forward to seeing how this works for you. I went the easier route and have line locks for each rear caliper on mine. Haven't had a chance to really test it out to see how it works yet.
Well, since Jeff shamed me in his build thread by showing his fancy-schmancy hammer organizer, I organized my pliers drawer this morning:
Actually, I had ordered these organizers on January 6 (well before his post), but they just arrived this week. Pricey, and horrible shipping time, but I do like them. The magnet keeps them from moving, and there's an orange "empty" slot indicator to catch your eye. You can see that here:
The picture above doesn't do it justice though, due to the angle and shadow. It's easily visible from the proper angle.
The sad news is I won't be making much progress on the build this weekend. The parts needed to continue the cutting brakes project didn't arrive, and I have some maintenance to do on the Expedition to get it ready for an annual backcountry camp trip to the South Park area in Colorado in two weeks to meet up with an aging, motley crew of backcountry friends.
And next weekend, my brother's in Dallas for work the following week (he calls northern lower MI home), so he's gonna drive down Friday night and hang out for the weekend. He's never actually been to our house since we moved in 17 years ago! He's a pretty handy feller, too, and he says he's up for helping on the build, so we'll see what progress I can make next weekend.
Stay tuned!
Actually, I had ordered these organizers on January 6 (well before his post), but they just arrived this week. Pricey, and horrible shipping time, but I do like them. The magnet keeps them from moving, and there's an orange "empty" slot indicator to catch your eye. You can see that here:
The picture above doesn't do it justice though, due to the angle and shadow. It's easily visible from the proper angle.
The sad news is I won't be making much progress on the build this weekend. The parts needed to continue the cutting brakes project didn't arrive, and I have some maintenance to do on the Expedition to get it ready for an annual backcountry camp trip to the South Park area in Colorado in two weeks to meet up with an aging, motley crew of backcountry friends.
And next weekend, my brother's in Dallas for work the following week (he calls northern lower MI home), so he's gonna drive down Friday night and hang out for the weekend. He's never actually been to our house since we moved in 17 years ago! He's a pretty handy feller, too, and he says he's up for helping on the build, so we'll see what progress I can make next weekend.
Stay tuned!
Another day is here. I've researched and found that the Kenwood KSC-PSW7EQ powered subwoofer is small, and it's 80W, just like the factory subwoofer, so I can use the existing wiring for it. Like I said in my last post, I'm not an audiophile, so I don't need thumping base. Does anyone know where I can find a 12-pin connector to wire up to an aftermarket subwoofer? I can pull one from a blown OEM subwoofer (late model), but I'm having trouble finding one. eBay is usually my go-to source, but there are only usable subwoofers there, and they are pricey. I don't want to scavenge the one off my good OEM subwoofer because it's still worth something (especially based on those eBay prices!) I'm hoping someone has sourced that connector from one of the electrical supply houses (like DigiKey, RS Online, etc.)
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