Pumpkin spice..
- Thread starter J Mack
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- #62
Pigeaten
GOLD Star
looks like the guy who stopped me last year coming back from Moab, came around a hill doing 75 with pig on trailer. I see a 3 police cars on side of road next to a 45mph sign.
cost me some big gas money
cost me some big gas money
Pigeaten
GOLD Star
The deeper JMack goes, the deeper we're in it
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- #65
Well if we do it right enough your next ticket will be for doing 75 in the PIG!
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- #66
I can grab some blinders and just focus on the painfully obvious stuff for a few days, I hear your state is importing fuel from the Bahamas after they ran all the refineries out and gas money is going to be an issue there before too long.
Pigeaten
GOLD Star
no, stay the course
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it's actually 1.43, but 1.5 is typically close enough.
180/3.14159 * ((casterLeft - casterRight / (SteerAngleLeft - SteerAngleRight))
The 1.43 comes from 180/pi to get radians 180/3.14159 = 57.295 degrees per radian and the 40 degree difference in steering angle
57.295 / 40 =1.432
I'm going to point out that you didn't get to quite 20 degrees left, but it doesn't make much difference in the calculated caster.
180/3.14159 * ((0.0 - 0.1) / (20 - -20)) =-0.143
180/3.14159 * ((0.0 - 0.1) / (20 - -15)) =-0.164
You can cross check (unless someone already did a cut and turn or moved the perches), by dropping the front driveline and measuring the angle of the pinion flange relative to vertical. (The mounting flange of pumpkin to the housing is the same, but that requires more work or being very, very careful.)
Pigeaten
GOLD Star
Pigeaten
GOLD Star
where's my slide rule?
I’m going with the reliable Abacus!
- Thread starter
- #72
Yes you are correct but when you're in the shop doing the work you just use 1.5, 1.43 is only used to win internet arguments.
I think it was a bit closer when looking from above than the angle I took the picture but yeah like you said it really doesn't matter for what we are doing here and the angle number on the gauge didn't change at all in 5° of rotation with the almost no caster in this front end . We used to do this with graduated bubble levels before readily available quality digital levels and didn't count small fractions of a degree and no matter the actual math or my example math this would be called 0° caster as a starting point and that's what I was trying to show the group that might not know.
You can argue that 0.15° and 0.143° are different caster numbers and neither is zero and you would be right but I'm still calling it zero when I start the work and I'll add full numbers from there.
I'll check that before I take it apart and post the information here, it will be interesting to see what we have on this un-known front end
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I did say “typically close enough”.
In drag racing, the rears may have positive static camber so when the weight transfers back and the rear squats, it cancels out the positive camber and lets the tires sit as close to dead vertical for max traction. The front axle on drag cars tends to run slight positive static camber so when the front end floats at the top end, the result is zero camber, as this makes for better E.T.s and trap speeds. One does tend to dial in a bunch of caster on a tube chassis drag car. As much as 9°-15° .
Drift cars also tend to run the rear with positive camber for similar reasons. Though they measure tire temps to set the suspension.
Same thing for trucks that carry heavy loads. Positive camber when empty, but when fully loaded with a 40T of load, the wheels are square.
Track cars tend to run as much negative camber as practical as it increases cornering loads
Some setups won't allow -20° and +20° steering angles, and then it gets kinda important to know where that "1.5" multiplier came from.
We did, but a half a degree was a fair callout.
The real question is how the trunions got so straight up-n-down.
Your post was timely, because the front end on Kalua (60 series housings, so the perches have been moved) are attached to Dobinsons springs. (I set aside the OME setup that came with the axles.). https://forum.ih8mud.com/attachments/img_8769-webp.4084654/
First time I’ve heard that “Dobinsons springs kill caster.”
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- #74
I'm just getting into these Dobinson springs but so far I prefer the OME front springs and for sure prefer the OME rear springs.
Dobson looks to have done some ****ery with the front shackle angle to control inversion ( minus a few degrees angle at full droop and plus a few at compression) so basically the shackle is backwards at ride height. They appear to use a lighter spring pack so maybe that's how they get away with the shackle angle and still have any ride quality. I can tell you bouncing on it you don't see any shackle movement and only see tire sidewall flex, I wouldn't be looking forward to driving on long fast fire roads with these.
I don't remember the exact numbers but when I looked up the caster numbers for my non-power steering pig it called for something around 1.5° caster, The longer front shackles needed for the longer main leaf in the lift springs removes a degree or so from an already low amount. So when I say the "Dobinson" springs also kill caster I'm referencing some conversations we've had that all lift springs most likely reduce what little caster you started with and should be addressed when planning a lift for a pig.
(Disclaimer) Don't use my numbers, math or anything else I say as the right answer for you. Check your parts and make the right decision for you.
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on the RMS lights. I run them on Pua'a Tua'a (they were on BATPIG first.)
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I was trying to figure out what you were talking about. So I went to take a peek.
Front end of Ornch:
I don't know what that dogleg on the shackle is. It's clear that it's trying to be anti-inversion AF,
Front end of Kalua (no weight on the suspension other than the frame) for comparison. Pretty sure this is Dobinsons, though I will confirm tomorrow.
ExitOffroad has a thread on this lift kit (I bought mine from @samc2447) and I don't see the dogleg on the shackles in the pics.
Here is the Dobinsons lift installed on a pig with 3rd leaf out.
@DTC72 says he runs a Dobinson's lift toward the end of that thread, and David's shackles don't seem to have that dogleg either.
Whoops.. that picture was before the lift.
There was a discussion 13 months ago: What did you do to your pig today? - https://forum.ih8mud.com/threads/what-did-you-do-to-your-pig-today.334904/page-314#post-15782470
and the shackles David had on his truck there look the same as the ones on Orinch.
If y'all want, I'll give you the set of the OME front and rear springs that I'm not going to use. I don't have the shocks, and you have to relocate the rear hangers (*), but it's clear you know what you're doing.
* go ahead, what's another few holes in the frame?
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That picture above of my truck is the before Dobinson lift kit picture, i.e. with the very tired original leaf springs. After a lot of research and hunting and asking, it appears as if the Dobinson lift kit is designed differently than OE. OE relies on the flex of the shackle thus the importance of the shackle angle. The Dob kit relies more on the flex of the actual leaf springs with little movement of the shackle. IF this is true then that explains the concerning shackle angle of the Dobinsons. I had no issues with the kit on last years Pig Party. I have not removed any leafs like Rocket City Cruisers recommended. Might I in the future...maybe?
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Yeah, found that as you were posting yours. Updated.
FJ55 front axle geometry and off the shelf lift springs do not work well together.
Nuff said. We’ve beat this subject with baseball bats and lead pipes on multiple occasions for decades now.
On with the C&T and suspension corrections!
Cut and turn!!
Cut and turn!!
Cut and turn!!
Nuff said. We’ve beat this subject with baseball bats and lead pipes on multiple occasions for decades now.
On with the C&T and suspension corrections!
Cut and turn!!
Cut and turn!!
Cut and turn!!
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- #80
This exactly what I'm dealing with here.
With full weight they are still back from vertical.
I would want them at vertical or slightly forward of vertical with no weight.
You hire some of the best guys around to work on these pigs for you and it will be interesting to see what you guys come up with.
On a side note did they look at caster numbers on this one yet?