Build JHF Trail Chassis

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woody said:
The shock tune all but eliminated that issue, since they are tuned to the suspension geometry and weight. It's stupid stable when vertical.
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I was just thinking about portals and suspension geometry. The forces generated in the portal gears and put on the axle housing are opposite those created by the pinion. On top of the fact that the diff gearing is reversed and as you mash the gas pedal the pinion is trying to go down instead of up like a standard axle. I guess its time for some math.
 
I am getting ready to start building a portal buggy and trying to use as many parts as I currently have and I wanted to get your thoughts on your crawl ratio. It looks like your current one is 75:1. Do you seem to think that is the sweet spot? I have a TH400 that isn't as deep as a 1st gear. Listed below is what I was thinking.

Crawl ratio:
2.48 x 3.8 x 1.92 x 4.56 = 82.5:1
2.48 x 3.8 x 1.92 x 4.10 = 74.1:1

I plan on using a 9" center. I think that either of these should work.
 
The V6 has a little more leeway with crawl ratio, since there is plenty of low end power to work with. 75:1ish has worked great, but I occasionally wish I was a shade lower. IMO, a deeper 4:1 case gearset would make me too low, and the 4.88 gears are claimed to be the strongest for the Toy diffs....so I'll likely stick with where I'm at :)
 
vogelj said:
I am getting ready to start building a portal buggy and trying to use as many parts as I currently have and I wanted to get your thoughts on your crawl ratio. It looks like your current one is 75:1. Do you seem to think that is the sweet spot? I have a TH400 that isn't as deep as a 1st gear. Listed below is what I was thinking.

Crawl ratio:
2.48 x 3.8 x 1.92 x 4.56 = 82.5:1
2.48 x 3.8 x 1.92 x 4.10 = 74.1:1

I plan on using a 9" center. I think that either of these should work.
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For what it's worth IMO, there's lot a factors that go into finding the "sweet spot" in crawl ratio, gearing is obviously a huge part of the equation but torque converts, motor, turbo, Superchargers... all play a big part in it,

I swapped a AW4 with a slightly lower than stock stall into a NA 2rz toyota pickup that ended up having a 75:1 Ratio with an atlas 5.0 it worked amazing.

I then got a portal car with a c4, slightly higher stall, Turbo ecotec and at 65:1 I could not get get use to it, I hated it in the rocks. I ended up swapping in a 4:1 Dana 300 and its much better at 99:1. I think even 75:1 would of been tough with my setup.

I personally prefer a little lower stall and the fear of driving through the brakes a bit vs a higher stall and always having to be on it to get into the power band but i could be the odd one out here
 
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mac33 said:
For what it's worth IMO, there's lot a factors that go into finding the "sweet spot" in crawl ratio, gearing is obviously a huge part of the equation but torque converts, motor, tubros, Superchargers... all play a big part in it,

I swapped a AW4 with a slightly lower than stock stall into a NA 2rz toyota pickup that ended up having a 75:1 Ratio with an atlas 5.0 it worked amazing.

I then got a portal car with a c4, slightly higher stall, Turbo ecotec and at 65:1 I could not get get use to it, I hated it in the rocks. I ended up swapping in a 4:1 Dana 300 and its much better at 99:1. I think even 75:1 would of been tough with my setup.

I personally prefer a little lower stall and the fear of driving through the brakes a bit vs a higher stall and always having to be on it to get into the power band but i could be the odd one out here
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Great points, I need to be in 2nd to have good braking. I run a stock HD/towing stall with the 700R. Crawls awesome, instant response at low rpm. The SC motor lights up as needed :)
 
woody said:
The V6 has a little more leeway with crawl ratio, since there is plenty of low end power to work with. 75:1ish has worked great, but I occasionally wish I was a shade lower. IMO, a deeper 4:1 case gearset would make me too low, and the 4.88 gears are claimed to be the strongest for the Toy diffs....so I'll likely stick with where I'm at :)
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Do you ever struggle with the very big jump to second gear @ 40.0ish to 1? I'm thinking about the rest of any trail in-between the tuff spots.
 
mustcamp said:
Do you ever struggle with the very big jump to second gear @ 40.0ish to 1? I'm thinking about the rest of any trail in-between the tuff spots.
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The 3.06 first and 1.63 2nd has never been an issue. 2nd has worked awesome for climbs when you need that power launch. And I frequently run between obstacles/trails in 3rd or even OD.

The successful attempt was 2nd gear, then dropping to 1st to control the crossover. Cold/damp that morning :)

 
I agree with you about the converter. I have a stock / HD Towing converter in my buggy, which is way better than the high stall converter I used to have. If the brakes get sketchy, I just bump neutral.
 
Oops...

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So simply, I fell off a climb. Big. Like, possibly, 20' or more. The front of the car is at the top of the photo, and the rear tires were above the crack you see in the right side of the photo.

I was fine. PRP seats and harnesses, and my Axel helmet, on as always. Not even bruised.

Simply, the front drifted to the drivers side (slick climb) and WAS hooking...then wasn't. I straightened the rear steer a bit (still slightly pointed driver) and kept a gentle throttle to push the car towards the drivers side and more possible front tire hook points. Never made it.

HARD drop/pirouette...landed on the hood/nose, solid. Roofline and A/B pillars are unscathed, the A/B/firewall of the chassis is still square.

The front isn't. Every tube is either bent or cracked or crushed...or all 3. Pics below are after a partial strip, prepping to take 'er down to Sand Hollow Off Road and let Steve and crew do the tubework.

Coolant disappeared (cracked that tube)....but once I reconnected the fuel pump relay wiring, it fired right up with no smoke. Steering column by the orbital is jammed into the head/valve cover, so it won't steer...but still drove it back to the lot and onto the trailer, forklift style.

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The lower main tube will be cut off at the firewall by the upper chassis front link mount, sleeved, and redone.

As you look at the pics, remember there are only supposed to be TWO bends total, in the lower/main rails, throughout this section. Instead, there now a dozen ;)

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woody said:
Minor adjustments.....

I had been using the ECU switching for the fan....however, it's a 5v ground circuit....when used with a 12v relay (wired for ground switching) it will eventually burn up those terminals (oops)

So my quick-fix was a $10 Amazon cheapo fan control sensor...claimed to turn on at 185 and off at 175....actually, on at 190-195 (gauge would climb to 210) and back off about 185-190. Dumb.

Upgraded today to a better quality Derale 16730 fan switch controller. Advertised at 180/165 and it actually came on around 185. Trail testing tomorrow, but the shop temp test worked perfectly. Also added a dash switch immediately next the ING toggle so I can turn it off (and actually hear people speaking without the fan running.....)
Amazon product ASIN B008VQGZAY
Have also ordered a pair of Carling 12v 20a switches to replace the two cheapo's I have installed now. And rubber booties too :)
Amazon product ASIN B07J5TLSD3
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i was playing this same game. vovlvo fan relay was the fix for me.
legit awesomness.........
 
chaplinfj60 said:
but it says each channel or circuit can only handle 20 amps. fans can draw more than that especially on start up. please do tell more about the solid state relay

:)
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I run two 20's tied together to a 10 or 12 ga wire for my radiator fan. (can't remember which without looking) Been doing this for 6-7 years with no issue. One of the circuits powers my trans fan. 4th is currently open.
 
Apparrently, reading a tape measure is hard. They had Logan's JHF car there for a week to copy and measure, and were off by an inch in a few obvious spots. W T F. And then I was called picky. W T F. And ZERO phone calls/contact during the process. I may have been out of town, but my phone works.

I shoulda done it myself, and likely still will. It's back there now to try and correct without cutting off the whole front and starting over. If they can get the drivetrain into the right spot instead of 1+" high and tilted, I'll likely redo the hood bars myself. I already relocated a few things to deal with the higher drivetrain, and it just kept compounding.

Jesse has SO many little tidbits into this chassis design, and many of those were lost. Sucks.
 
Blase said:
Damn that sucks!! Very hard when you are a builder to have someone else do work that's the way you want it. Especially when you're as good a builder as you are.
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I"m a hack, which is why I took it elsewhere :) But yes, it was beyond frustrating....and won't happen again.
 

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