Moon Patrol Buggy Build

[YeeP]

Here are my link numbers. Looking back, my rolling radius is optimistic, so I should probably update it with a more realistic radius. My thread is Here, but not much has been happening with it lately.


Now that I look at my numbers again, my chassis builder only specifies 9" of vertical separation in the front. What is your target belly height again? I added mine (19") as a parameter in the calculator and have all of my chassis-side mount heights (Z) as a function of the belly height, and have all of the axle-side mount heights as a function of the rolling radius of the tire. The heights for your mount centerpoints for both ends of your lowers is below the centerline of your wheels. I was suggesting raising them purely from clearance perspective. Having the axle end mounted above the centerline of the wheel helps keep your link angle flatter assuming your belly isn't way below your wheel centerline.



There are definitely lots of people running black, so don't let me shit all over your color choice if you like it. I just personally wouldn't consider black

My planned belly height is at 17". Probably why you are seeing what you are when compared to the center line of the wheel.
I came up with this value kind of based on what I typically wheel with on the harder stuff. My one buddy is super low at 14.75", and the other buggy I really like is at 16".
So did you write your functions in the spread sheet just to match the rolling radius of the tire (so they were always flat)?

Edit: currently my lowers are downhill toward the axle, by a half inch over 32". So pretty flat.

So just so I understand your idea on this, if I were to re-word what you said, you have moved the axle side lower upward from where I am at, really in an effort to get the bottom of the control arm flat with the bottom of the axle tube. I kinda made some assumptions there, but Im guessing that is the goal.

 

[chaplinfj60]

are you talking about this angle? because if you are my understanding is you need to be over 45 in the total. but i dont know but reguardless these angles work well for me.

 

[YeeP]

are you talking about this angle? because if you are my understanding is you need to be over 45 in the total. but i dont know but reguardless these angles work well for me.

Yeah, I did talk about that. The consensus seems to be: you want a total greater than 40, to achieve enough triangulation that your control arms provide an acceptable mechanical advantage to overcome the lateral forces act on it without the need of a track bar/panhard. The closer you are to 40, the more force your components will have to endure to keep the axle in position.

At least, that is understanding of it.

 

['84 Bronco II]

My planned belly height is at 17". Probably why you are seeing what you are when compared to the center line of the wheel.
I came up with this value kind of based on what I typically wheel with on the harder stuff. My one buddy is super low at 14.75", and the other buggy I really like is at 16".
So did you write your functions in the spread sheet just to match the rolling radius of the tire (so they were always flat)?

Edit: currently my lowers are downhill toward the axle, by a half inch over 32". So pretty flat.

So just so I understand your idea on this, if I were to re-word what you said, you have moved the axle side lower upward from where I am at, really in an effort to get the bottom of the control arm flat with the bottom of the axle tube. I kinda made some assumptions there, but Im guessing that is the goal.

I forgot you were running your belly so low.

All of my chassis mount heights are relative to the belly height, and all of my axle side mount heights are relative to my tire rolling radius. That way I only have to change one number insted of going and editing each cell to adjust everything every time I tried adjustment to my belly height or tire rolling radius.

I just opened my actual spread sheet again and I had already adjusted my tire rolling radius to 19" like you have been using, and apparently, those screen shots I quoted from the "How are My Numbers" thread had some guesses on my part about the link locations. Here are the final numbers with verified measurements:

Raising the lower above the centerline of the axle also helps with ground clearance, but as you pointed out, your links are already flat. Part of my suggestion to raise the lowers was due to my ignorance on how low your belly was.

 

[YeeP]

Alright guys, I made some good progress yesterday and actually solved an issue that has been plaguing me.

So I got all setup to check just how wide. I could get these damn control arms on the axle. I noticed: even with the control arms within 1/8" of each other when distance from the center of the axle was compared, the "tire" hit a control arm on one side and not the other. This happened a couple months back on an earlier mockup and I believed it was caused by the axle not being centered properly on the table in relation to the chassis. That is why I made that line down the center of the table. Since this wasn't the case now, I just worked outward from center with measurements.
Center of axle to center of king pin - within 1/16" on each side.

Then it hit me, what if one knuckle turns more than the other? I considered cutting the inner-Cs off and measuring them on the table again, but then it hit me, they should end up with the same distance to the tie rod bolt from center, when fully turned outward to lock. They did not....

Also, this was something I was concerned about when I bought these high steer arms, JHF does a cool "service" to customers by posting on their site that if you buy their arm and have a ram with X amount of throw, you will achieve a specific angle. Well, with the knowledge that I was not hitting the same angle, I thought that I should probably confirm that the angle I do it is achievable!

Luckily, I remembered I bought those TMR alignment brackets last year for like a black friday deal. So I got them out and got the toe set at zero on each side. Then I turned each side out 4.5" based on a measurement from my current ram mount. This time I ain't messing around with getting inconsistent results in measurement.

Temporarily locked those SOBs into what will be my achievable full lock.

While this is slightly upsetting as I know I cannot quite hit 45 degrees like I had planned, it did open up some options to where I could move the axle side lowers closer to the Inner-C. So, I grabbed some 2.5" OD pipe I have in the garage, and figured out where I could mount the joints and still clear the tire. Here is an updated version of my numbers.

Bebop and I talked about how inaccurate the CG guess is. I agree, but it is what I have to work with in front of me.

'84 Bronco II I noticed you have your CG like 2 inches lower than mine. Care to share how you came up with that number?

So as far as the numbers, the immediate things I see:
Good

• Increased convergence
• Lower arm length now slightly above 36"
• Horizontal separation of lowers close to 40" per '84 Bronco II suggestion

Not Good

• Roll Center has come down about 1.5 - 2 inches throughout the graph. It is my understanding that I should shoot for a roll center that is near 80% of the CG height to decrease body roll. Anyone have an opinion on this?

Here is a shot of the old setup roll center graph:

• With the lowers only just under 8 inches apart at center, I will have a minimal location to start the skid plate for the oilpan that needs to eventually be 11" wide at the pan. This skid has to start there because the trans adapter/starter are actually the lowest part of the drivetrain currently. I think I can get creative here and will know more when I can flex it, but moving the lowers, chassis side, outward might be needed. I can imagine connecting to the crossmember outside of the link mounts, then going over them and back down to make a skid plat mount.

I also took Bebop 's suggestion and created some telescoping mock arms. These are just the lowers, but the can go from 40" down to about 28", so they should work for this project.

I cut all lower mock tabs off and smoothed out the welds. Just kind of waiting to see what people think on this so far.

'84 Bronco II - I created some more tabs for the axle side uppers that are ridiculously tall just so I can test to see how high I have to get to clear the pinion while cycling.




Quick question for anyone:
I have no chassis above the axle to get an accurate 6" of up travel estimate. I have been measuring from the table to the bottom of the axle at ride height, then just adding 6", but I feel that this is inaccurate when talking about how the axle would hit the bump stop at an angle. Im considering taking a piece of scrap and tacking it to the chassis, parallel to the table, that goes out above the axle so I can have an accurate measurement from the top of the axle, where I am assuming I will put the bump stop pad.
Thoughts?




Tool Update
EDIT: random addition I forgot to add. I am using the crap out of this old cherry picker I borrowed from my Dad. The steel caster wheels were not in good shape. So I upgraded it to some nice casters that roll almost too smooth.

 

[Bebop]

Not Good

• Roll Center has come down about 1.5 - 2 inches throughout the graph. It is my understanding that I should shoot for a roll center that is near 80% of the CG height to decrease body roll. Anyone have an opinion on this?

Intellectual masturbation.

• With the lowers only just under 8 inches apart at center, I will have a minimal location to start the skid plate for the oilpan that needs to eventually be 11" wide at the pan. This skid has to start there because the trans adapter/starter are actually the lowest part of the drivetrain currently. I think I can get creative here and will know more when I can flex it, but moving the lowers, chassis side, outward might be needed. I can imagine connecting to the crossmember outside of the link mounts, then going over them and back down to make a skid plat mount

I would build the horizontal tubes of the skid right now. The place the link mounts.

I also took Bebop 's suggestion and created some telescoping mock arms. These are just the lowers, but the can go from 40" down to about 28", so they should work for this project.

Cool !

Quick question for anyone:
I have no chassis above the axle to get an accurate 6" of up travel estimate. I have been measuring from the table to the bottom of the axle at ride height, then just adding 6", but I feel that this is inaccurate when talking about how the axle would hit the bump stop at an angle. Im considering taking a piece of scrap and tacking it to the chassis, parallel to the table, that goes out above the axle so I can have an accurate measurement from the top of the axle, where I am assuming I will put the bump stop pad.
Thoughts?

Wait until the links are done and shocks are installed before you measure.
You need 6" of shock shaft uptravel.
Not 6" of axle uptravel.

 

[YeeP]

Intellectual masturbation.

Im assuming this is only in reference to the CG height based references and outcomes. Not the fact that roll center height and cg height differences do have an affect on the suspension performance. If so, , if not, please splain it.

I would build the horizontal tubes of the skid right now. The place the link mounts.

I guess the way I was seeing it, their placement (horizontal tubes) will be dependent on where the arms are cycling. In addition, I have no chassis to attach them to at this point in time.

Cool !


Wait until the links are done and shocks are installed before you measure.
You need 6" of shock shaft uptravel.
Not 6" of axle uptravel.

True and good point. Then to be more accurate; I need an upward stopping point with the axle where I can say: "If the pinion hits the control arm when the axle is higher than here, it won't matter because its travel will be limited at this point". That is the issue I am trying to solve there.

 

[Bebop]

Im assuming this is only in reference to the CG height based references and outcomes. Not the fact that roll center height and cg height differences do have an affect on the suspension performance. If so, , if not, please splain it.

No. No point in masturbating when you could be making progress in the shop.

I guess the way I was seeing it, their placement (horizontal tubes) will be dependent on where the arms are cycling. In addition, I have no chassis to attach them to at this point in time.

Lower tubes. You can build them.

True and good point. Then to be more accurate; I need an upward stopping point with the axle where I can say: "If the pinion hits the control arm when the axle is higher than here, it won't matter because its travel will be limited at this point". That is the issue I am trying to solve there.

I'm sure with 6" of uptravel your links won't be hitting the pinion.

 

[Sterlingfire]

For bump stop pads i learned that using flat plate will just limit your travel on articulated bump... radius-ed is the only way to keep articulated travel very close to the vertical travel numbers. Mine came within 1/4" of each other...

 

[YeeP]

No. No point in masturbating when you could be making progress in the shop.


Lower tubes. You can build them.


I'm sure with 6" of uptravel your links won't be hitting the pinion.

They did in the original setup. This is why I moved the uppers outward on the axle

 

[YeeP]

For bump stop pads i learned that using flat plate will just limit your travel on articulated bump... radius-ed is the only way to keep articulated travel very close to the vertical travel numbers. Mine came within 1/4" of each other...

I was thinking the same. Got any pics?

 

[Sterlingfire]

Im assuming this is only in reference to the CG height based references and outcomes. Not the fact that roll center height and cg height differences do have an affect on the suspension performance. If so, , if not, please splain it.

I guess the way I was seeing it, their placement (horizontal tubes) will be dependent on where the arms are cycling. In addition, I have no chassis to attach them to at this point in time.


True and good point. Then to be more accurate; I need an upward stopping point with the axle where I can say: "If the pinion hits the control arm when the axle is higher than here, it won't matter because its travel will be limited at this point". That is the issue I am trying to solve there.

Time to at the very least mock up your front frame area so you can attach shocks and bumps... maybe you should focus on that instead of axle placement at this point. You really need a frame for reference. If you can't mock shocks then you can't do more then you have IMO

 

[Sterlingfire]

I was thinking the same. Got any pics?

That's all i got. I'll try to get better ones tonight.

 

[chaplinfj60]

is the bump can mounted in the same plane as the Coil Over. parallel basically ?

 

[Sterlingfire]

is the bump can mounted in the same plane as the Coil Over. parallel basically ?

Yes, but as the axle rolls the bump pad changes height. That's why i used the tube as the pad.

 

[Bebop]

They did in the original setup. This is why I moved the uppers outward on the axle

Now they are outside and raised, they won't hit.

 

[Sterlingfire]

Yes, but as the axle rolls the bump pad changes height. That's why i used the tube as the pad.

To further articulate, as the axle moves through the suspension arc the coilover changes plane, especially when fully bumped to one side and fully drooped to the other side.

 

[YeeP]

Yes, but as the axle rolls the bump pad changes height. That's why i used the tube as the pad.

ok I see it now. Man I was like where the hell is it. lmao. That totally makes sense and was an issue that I dealt with on my CJ.

 

[Treefrog]

How much the axle roll affects where the bumps stop hits is controlled by where the shock mount is. if the shock is more inboard, the pad will have upward movement with roll. Having the shock more outboard is riskier since the shock will compress more in axle roll. If they are inline, the movement in minimized.

 

[Treefrog]

As far as the "minimum" convergence angle, I've seen 40-45° thrown around, but that is a rule of thumb. Probably not a bad rule of thumb, but less convergenge angle just means side loads are going to put more force on your links.

because if you are my understanding is you need to be over 45 in the total.

The generally accept minimum seems to be 40 degrees. I have read that someone on the Pirate4x4 forum derived a value of either 37.5 or 38.5 degrees. I have never been able to find said derivation.

If you are expecting that you might take some larger sideways hits or have a lot of sprung weight, it is a good idea to go higher.

 

[Treefrog]

When dealing with link length, pay attention to how it is being measured. I think the length recommendations are generally in side view, not in physical length.

 

[YeeP]

When dealing with link length, pay attention to how it is being measured. I think the length recommendations are generally in side view, not in physical length.

Well damnit, that doesn't make me feel better. I was under the assumption that it was a reference to the true length. The only way I can do that then is to push the axle forward.

What is your take on the change made above?

How much the axle roll affects where the bumps stop hits is controlled by where the shock mount is. if the shock is more inboard, the pad will have upward movement with roll. Having the shock more outboard is riskier since the shock will compress more in axle roll. If they are inline, the movement in minimized.

"axle roll" on the calculator can be indicated by the pinion change graph correct?

Treefrog - Im going to have to go at least 4 inches higher on the front upper, axle end Z to clear the pinion. Is this an exercise in futility? By adjusting the Upper front axle Y back to 11, and the upper front Z 4 inches up (assumption). My AL/AD is back up in the 60 to 70% range. Front roll slope is back around -13. It does bring the roll center back up to 29 which I like for my assumed CG height. Pinion change is much more aggressive, probably because of the steeper downward angle of the upper toward the chassis.

 

[Treefrog]

Well damnit, that doesn't make me feel better. I was under the assumption that it was a reference to the true length. The only way I can do that then is to push the axle forward.

What is your take on the change made above?

Looks ok, I guess. I don't see anything that sticks out as odd or alarming with the front. It looks like the side view length is ~32". Its on the lower end, but its not in flashing red lights territory.

"axle roll" on the calculator can be indicated by the pinion change graph correct?

In this case I am talking about the axle rolling side to side in the front view as it flexes with one side at full up travel. Isn't 3d fun?

Treefrog - Im going to have to go at least 4 inches higher on the front upper, axle end Z to clear the pinion. Is this an exercise in futility? By adjusting the Upper front axle Y back to 11, and the upper front Z 4 inches up (assumption). My AL/AD is back up in the 60 to 70% range. Front roll slope is back around -13. It does bring the roll center back up to 29 which I like for my assumed CG height. Pinion change is much more aggressive, probably because of the steeper downward angle of the upper toward the chassis.

I am not able to take a closer look at his at the moment, but usually you want the front AL/AD to be low to help suck up bumps when on the brakes. Arguments can be made on the validity of this for a crawler. What does it do as the suspension compresses? A higher roll center rolls less, but gives less warning about tipping over.

Try moving the lower axles up a hair with this it might help offset the steeper upper.

 

[Bebop]

A higher roll center rolls less, but gives less warning about tipping over.

Ever seen what an old school CE moon buggy with a very high roll center would do on high off camber situations ?
I had one (Roxanne, built for Cody Wagoneer) and the pucker factor was real

 

[Treefrog]

Ever seen what an old school CE moon buggy with a very high roll center would do on high off camber situations ?
I had one (Roxanne, built for Cody Wagoneer) and the pucker factor was real

Can't say I have. At risk of derailing, and maybe we should take this to a different thread, can you share what it would do?

 

[Sterlingfire]

How much the axle roll affects where the bumps stop hits is controlled by where the shock mount is. if the shock is more inboard, the pad will have upward movement with roll. Having the shock more outboard is riskier since the shock will compress more in axle roll. If they are inline, the movement in minimized.

Makes sense when you think about the geometry of it... but some of us are relegated to run the shocks where they are because of using an existing frame(read stock). My shocks are more outboard on the axle to keep from contacting the frame at full Articulated bump. They are within 1/2" of contact. My bumps are inline with the shocks, but obviously my axle roll affects where they land, so a tube pad is my compromise to not lose vertical travel.

 

[Sterlingfire]

ok I see it now. Man I was like where the hell is it. lmao. That totally makes sense and was an issue that I dealt with on my CJ.

These are the pics.... the thin tube is only for mockup. I have schd 80 to use for final. I'm also going to strap across the top of the link mount so it doesn't push it apart.

 

[chaplinfj60]

your bump hits here, on this piece of pipe.

 

[YeeP]

Yeah I kinda figured that. 👍

 

['84 Bronco II]

'84 Bronco II I noticed you have your CG like 2 inches lower than mine. Care to share how you came up with that number?

I know I put some thought into that number but I forgot exactly how I arrived there. I think it is based in the height of the camshaft and mounting the drivetrain as low as possible with a 19" belly. I actually measured the C.G. height on my race Bronco (3" lift and 29" tires) before tearing it apart, and it was around 31-32" off the top of my head, so I think 30" for a buggy is fairly realistic.