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Thread: Ramination's FJ40 Buggy Build

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Old 01-24-2014, 09:23 AM   #61
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Default Re: Ramination's FJ40 Buggy Build

So, last night I got a little time to work on this thing again to prep for this weekend. I wanted to tweak my suspension a little, and go a little bit softer. Being a nerd (and engineer), I couldn't just try different spring setups. No, that definitely is out of the question, math must be involved.

My thought on suspension setup for something like this rig is to run the lightest spring rate as possible that will yield the ride height I am trying to achieve with ~0.25" of preload; this should limit the "unloading" the suspension may want to do in an off camber situation, I think. And then of course let the shock oil do the dampening duties, not the springs. I only mention this because it seems like this is NOT the strategy the majority of people in this community follow.

Anyways, in order to tune the spring rate down, I first have to know what the spring rates of these KING springs are. Since I couldn't find anything on this, I broke out the pen, paper and TI-89 calculator and did it myself. I wont bore you with the nerd stuff (shear modulus, Poisson ratio, etc...) but essentially you take the spring diameter, number of active coils and the coil thickness and throw them into an equation with the shear modulus and BAM...spring rate. I'll skip that unless there is some interest.

Once you have the spring rate of a spring, you can find the combined spring rate of two springs together using the formula = (Spring Rate A x Spring Rate B)/(Spring Rate A + Spring Rate B).

I then decided that I had might as well do it for as many springs I could get my hands on...because why not? So, fired up Excel and got to work measuring all I had. I don't have a lot of the Axial springs, but I would like to add them in if I can. I am going to start a separate thread asking for people who have these springs to get my the dimensions. The numbers in red are just guesses for now...

So I was set up with a Stock over Black 40mm King spring. (the 40mm springs are for the 110mm shocks, the 35mm are for the 100mm shocks), which results in a combined ratio of 1.595 lbf/in (according to my calculated spring rates, which may or may not be correct but the relationship will still follow). I wanted to go a little softer up front and a little more softer in the rear, so I went with a White on top of Black for the front (1.348lbf/in) and a White on top of Red in the rear (1.174lbf/in). These 3 conditions are highlighted in the chart.

Now typically I wouldn't want the individual spring rates of the two combined springs to be so far apart, and so for the front I originally tried a Stock over Red (1.357 lbf/in) but I actually didn't like how that flexed. For all intents and purposes, the Stock over Red and White over Black are essentially the same combined rate, but due to the individual rates they feel different. I know in the 1:1 world you typically avoid having a large difference between the two springs, however maybe this is something we can get away with in the 1:10 world.

I will break down corner weights are how that effects the shock/spring setup later, if there is interest. For now, chew on this (if you can read it, I uploaded it full size but photobucket isn't allowing you to view it that big).





I also got some Grip Fab V1 lockers in the mail yesterday and installed. Actually I only had the energy to install the front one. Rear later. Shit is tight now.



And finally, being married is paying off, soft top made and installed. I like the soft top on there A LOT, because it helps hide my shitty interior work.


Last edited by Ramination; 01-24-2014 at 09:31 AM.
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Old 01-24-2014, 09:54 AM   #62
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Default Re: Ramination's FJ40 Buggy Build

She really turned out beautiful. You have a super talented wife...nice work. Just overall great build.
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Old 01-24-2014, 10:33 AM   #63
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Default Re: Ramination's FJ40 Buggy Build

Nice rig!
I just "finished" my hard body aoshima c2 rig and wanna start a c2/3 basher.
Urs is great inspiration!
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Old 01-27-2014, 07:56 AM   #64
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Default Re: Ramination's FJ40 Buggy Build

Where to start...well, how about the fact that I drove this thing ~11 hours this past weekend? I learned a great deal about this rig, and I like it. The suspension felt right on the money, I was surprised how well it absorbed crossed up hits of obstacles at speed, pleasantly surprised.

Let's do some pictures first.








I loved this climb and sequence.












My favorite from the weekend:




More pictures here Pictures from Belle and Forrest Hill Park Jan 2014



I had one small issue on Saturday, I broke the axle housing on the front drivers side. Luckily, the beeftube held everything together and I was able to keep going...sort of. The beeftube spun in the housing with every change in steering but nevertheless I was able to drive it back to the truck.



Long term I will replace the housing, but since we were going back out Sunday I drilled and tapped the backside of the housing and beeftube to allow me to put a set screw in place to hold the tube from twisting in the housing. Worked perfect for multiple hours of abuse. I may do this on the new housing too just because.

Last edited by Ramination; 01-29-2014 at 07:54 AM.
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Old 01-27-2014, 07:58 AM   #65
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Default Re: Ramination's FJ40 Buggy Build

I have no choice but to compare this rig to the FJC, although they are nothing alike. Besides one being a purpose built buggy and one being a "heavily modified SUV". When I look at the way they are built, it is a no wonder they act so different. The FJC is brushed, minimal flex, small TSLs and a neutral weight bias. The FJ40 is brushless, tons of flex, big ol Pit Bulls and a front weight balance. The crazy part, is that with the exception of an obstacle or two they are pretty much equally capable. I'm not sure if that means I built the FJC really well, or the FJ40 really poorly but neither cease to amaze me.

On the rocks, I do miss the torque of the brushed motor when you are in a tight spot at 0 RPMs, but to me this rig screams brushless. Even if I ran it on a 35t and 4s like the FJC it wouldn't have the wapow or wow factor the brushless give the rig. I am considering a 4 pole motor though...

For the 40, I think my next moves will be to do CMS, add a spare tire mount to the rear (it was only Ziptied this weekend) and then build a new hood. I want the hood to fit a little tighter...oh yea and I want to build it out of metal this time. Stay tuned...

Last edited by Ramination; 01-31-2014 at 09:24 AM.
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Old 01-27-2014, 09:24 AM   #66
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Good looking build

Sent from my VS980 4G using Tapatalk
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Old 01-27-2014, 11:33 AM   #67
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Default Re: Ramination's FJ40 Buggy Build

wow, rig turned out great. good to hear it performed well for you. i've got the exact same axle issue with my Honcho right now, hahaha!
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Old 01-27-2014, 11:38 AM   #68
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Default Re: Ramination's FJ40 Buggy Build

Thanks!

I think 3s w/brushless + Grip Fab Locker + 17 degrees outside = too much for the plastic housing.
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Old 02-11-2014, 06:31 AM   #69
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Default Re: Ramination's FJ40 Buggy Build

Had some pretty good carnage to the front axle this past weekend.



(Note that the right side c-hub mount is completely gone)

Somewhere along the line, before the servo post ripped off the housing, the passenger side of the stock locker gave out and left me at 75% capacity. Didn't stop wheeling though, kept pushing with the other rigs in the group but eventually broke the hex pin on the other side then the servo post. Drove it most of the way back to the truck still though.

That is the axle that used to be in the FJC, so it has LOTS of hours on it. I am not sour about that breakage at all.

New housing, FI Spools, and XR10 shafts are on the way for this weekend!
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Old 02-11-2014, 06:47 AM   #70
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Sorry Bo.

Last edited by n8welch; 02-11-2014 at 07:22 AM.
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Old 02-11-2014, 05:18 PM   #71
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Default Re: Ramination's FJ40 Buggy Build

Sweet fj 40 bro
Should rock a white top
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Old 02-11-2014, 05:18 PM   #72
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Default Re: Ramination's FJ40 Buggy Build

So it still looks like a port a potty ha
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Old 02-11-2014, 05:45 PM   #73
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White canvas top!
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Old 02-11-2014, 08:15 PM   #74
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Default Re: Ramination's FJ40 Buggy Build

sick rig man! Im working on building something very similar. For the hood I have a tamiya fj40 body and i made a resin mold from in order to form an aluminum hood and cowl. Love the way this rig looks has me second guessing using a scx10 frame as my starting point.
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Old 02-12-2014, 06:06 AM   #75
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Default Re: Ramination's FJ40 Buggy Build

Quote:
Originally Posted by kyle4130 View Post
Sweet fj 40 bro
Should rock a white top
Oh yea? Something like this guy's?



If you're into FJ40 buggys or just a good read check out his build, its pretty awesome A Fool and his Money - Pirate4x4.Com : 4x4 and Off-Road Forum

Quote:
Originally Posted by MIKO View Post
White canvas top!
Next one is going to be Al

Quote:
Originally Posted by Falon View Post
sick rig man! Im working on building something very similar. For the hood I have a tamiya fj40 body and i made a resin mold from in order to form an aluminum hood and cowl. Love the way this rig looks has me second guessing using a scx10 frame as my starting point.
Thanks! Have you made the hood and cowl yet? I would be very interested in working with you to get a metal hood for this thing. I tried forming some Al over my styrene hood but it was an epic fail. Are you doing it like MetalMasher does it?

The SCX frame is a good starting point, and will do you well I think. The only reason I didn't go that way is because I was trying to save a few dollars (lol!) and I like the challenge of doing everything the hard way. In addition, I get more uptravel at lower ride height compared to a SCX frame (unless you hacked off the front and rear and only kept the middle). That's really the only benefit I get from the custom frame, but I'm sure you could rework a SCX frame to do the same.

Last edited by Ramination; 02-12-2014 at 06:14 AM.
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Old 02-12-2014, 06:39 AM   #76
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Default Re: Ramination's FJ40 Buggy Build

The scx frame will be hacked off front and rear basically just the link mounts and my motor/tranny mount in the front. Yes I'm doing it how metal masher does using the lexan body to make a resin mold then forming an al panel over the resin mold. I'm just using a tamiya grill though.
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Old 02-14-2014, 11:02 AM   #77
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Default Re: Ramination's FJ40 Buggy Build

Mmmm, out with the grip fab and Axial junk, in with the FI spools. Got them both installed last night. Tight, tight, tight.



Other than the spools, everything else will be the same as before on the 40, mostly because I didn't have time to change anything, but also because it has been working so damn well.
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Old 02-18-2014, 06:56 AM   #78
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Default Re: Ramination's FJ40 Buggy Build

So, the FI spools are really great! I do think they are the reason my slipper loosened up after about an hour of driving though. The driveline is so much tighter now than it was before that now when I am turning sharp there is significantly more force on the driveline, especially with the overdrive front, that I can hear a difference. I am going to really crank down on that thing for this weekend (although it was 100% tight before) and see if it lives. If not, that slipper is gone!

In a quest to be more scale, I will be going CMS, but I still need to figure out a way to disguise the motor. There have been a few shots so far where the motor peaks out under the slider, like this.



I am open to innovative suggestions.



Since we're already here, how about a few more shots



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Old 02-18-2014, 10:32 AM   #79
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Default Re: Ramination's FJ40 Buggy Build

Rig looks great!
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Old 02-18-2014, 11:31 AM   #80
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Default Re: Ramination's FJ40 Buggy Build

solution to hide motor: boatside skid plates.

what was the problem with the Grip Fab locker vs the Locked Up spool?
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