A-ARM help

myths prepetuated by more myth's?

Momma always asked you that if your buddies jumped off a bridge, would you jump too? Most people answer no to the first question but will still buy LT setups simply because they believe someone's recommendation that something is better. Everyone sees that YFZ's are "race ready" from the factory so they want YFZ shocks on their bikes. Companies make arms to fit YFZ shocks on other bikes and because the YFZ shock is 15 3/4" (longer by 1" than the 14 3/4" banshee/blaster/warrior shock) they call them LT. The myth perpetuates.

I'm not claiming to know more than anyone else about suspension. I just don't have any preconceived notions about the way suspension "is supposed" to work... If you have 14" of travel out of your suspension components (and I mean the joints and tie rod ends) you could control that completely with the properly sprung/valved shock with only 2" of travel. Completely possible. Hell in the effort to save space, some european vehicles don't even use linear shock absorbers! They use a fluid gearbox (akin to a door closer) to put resistance on the suspension travel, look up rotary dashpot.

Oh, and I'm not saying long travel is junk... I'm saying that the desire to have rebuildable shocks on a bike that came without them is understandable. (I too would like to have YFZ shocks simply so I could pull them apart each spring and freshen them up). Companies who make arms to fit factory shocks call them standard and then the arms that are made to fit the longer (and rebuildable) shocks are called long travel. They had to name them something. What I am saying is that using the (possibly) wrong shock combo for your riding style simply because they are 18" long is foolish. You're better off using a properly sprung and valved standard travel combo will net better results. If the 18" shocks are the correct spring and valving ratio they will stay cooler in extreme use than the standard travel shocks but that's not enough of an advantage to use them IF they are the wrong combo.
im not gonna be using these shocks just to say hey i have 18" shocks im cooler than you, im wanting to use these because they are more tuneable than the elkas i have, the floats have rebound control and my elkas dont. if i do get to race this bike rebound control will be helpful to tune for different tracks and terrain unless having rebound control is a myth too. if my elkas were as advanced as the floats i wouldnt even consider changing. anyways back to the topic the arms look good.
This is one of the things I like about The Blaster forum, willing to try different things, home fabbing, mix and mingle different parts I:I. One thing I didn't figure out is are you using innershield (flux core) wire or gas shielded wire? Are you using correct wire for the 4130?(alloy?) For being initial prototype I think they look good!! From what I see, other suggestions, and my own ideas I might try something a little different. I have also been kicking the idea of making extended J-arms for my son's 'shee, $450 for a set of arms is a bit pricey weather for a Blaster or a 'shee. :eek:
My welder was running innershield so I burrowed my buddy's welder with 75/35 gas.

With no prior history with this machine I went to welding these arms... I think they turned out delightfully (if I don't mind tooting my own horn)

I'm using standard ER70S-6 wire. That's the wire recommended by chassis builders for 4130 alloy. Thankfully nothing really funky for welding wire. `
So I have an initial ride report. No jumps, just a lot of pounding through very tall grass clumps (which with my big butt on it is pretty rough in it's own right).

It was fairly pretty here Saturday, about 50 degrees F with nearly clear skies so perfect riding weather. I took the blaster out and my buddy took out his Bayou 250 (I know, I know, perfect drag racing competition HAHA) and we went out to check on his livestock out on his land. He's got 33 acres of uncut grassland so we went and tore that up for a few hours.

There is absolutely nothing to report other than a bolt falling out of the heelguard (forcing the heelguards early retirement but the blaster kept riding) and that banshee shocks and extended arms aren't rated to carry what I weigh (but did so without a complaint). I rode for about 3 hours until I was covered in speckles of mud and tired of cutting up through the field in 4th gear getting pelted by seeds from some unnamed grass stalks. I carried goggles and it still wasn't enough, my buddy wore overalls and had to get off his quad a few times and shake the seeds out of his draws.

The paint I painted the tubing with was rubbed off nearly immediately by the grass tufts I was hitting at about 40MPH so I know at some point I'm going to have to do something about that...

I have decided to change my lower shock mounts...again. They worked great but I see ways to improve the strength and positioning of the lower shock mount without adding too much weight or too much complexity.
Thank you sir. I appreciate any feedback (but especially positive haha)

I still have all the measurements to finalize and post. I'm waiting on finishing acezeesawtooth's set before I post up the final stuff. I want to make sure each measurement is exactly right before I hand them over. Once I have more pictures and the measurements finalized, I'll be posting it all up in this thread.

In case you're interested, I'm going to be building sets too. The thread in the for sale section: http://www.blasterforum.com/sale-18/3-1-arms-35780/
i just read this whole post, great stuff bro, and a continuing learning process
i did though, right off notice all the threads sticking out on the lower ball as a weak point, are the newer arms gonna be a tad longer to compensate for the ball threads ???
or just a longer tube ????
Both, actually.

My arms I used two 16mm x 1.5 nuts welded together to form my "tube" to thread the lower ball joint into because I didn't have any source of a piece made to do the job and the reason I stuck so much of the threads out on my set is because I was "measuring" the amount needed to stick out by making the arms and then adjusting the ball joint to correct the camber. Now that I know how many threads need to stick out to give a little bit of camber adjustment (probably 5 degrees) I have remade the jig to that size and I found a supplier who sells the ball joints and a threaded bung made to be welded into an arm for a reasonable price. That's one of the things I'm going to be taking bunches of pictures on this afternoon when I finish one of the lower control arms.

That's one of the major changes to the arms I've made as well as changing the jig to a +1" forward instead of just +3 out.
I've been to their site before but their a-arm parts are more for heim parts instead of ball joints.

I got my lower ball joints with the weld in bungs from Stellar Machine.

Home Page

They make a lot of a-arms for banshees but the lower ball joint on the banshee and the blaster are the same. Getting up with the owner, Tim, is a little bit of a challenge (apparently he's VERY busy building stuff) but once you do he really comes through. Talking and dealing with Tim reminds me a lot of talking and dealing with Ken O'Connor. He's busy, he's got WAY better things to do than answer a million and one questions but you still never feel rushed and he doesn't answer question half-assed he explains anything needed.

Anyway back to the project... I went outside and made a lower control arm while I wasn't on here. I haven't done the math for a stock shock yet so I haven't welded in the cross bar and shock mounts yet but the bulk of the a-arm is done

I just took some pictures:

+3 +1:

Believe it or not, I didn't use the factory ball joint angle as a guide, I figured out the bottom out point on the upper ball joint and then figure out where to weld the lower ball joint to keep it happy in arc with the upper ball joint but look how close they turned out:


The weld in bung from Stellar and my welder turned up on 4 out of 4 heat range:


The pivot point welds and cross bar:


According to the measurements, the ball joint is at the correct distance out with only those three threads showing now. It'll give ~ 5 degress of camber correction but I don't think it's sacrificing too much strength like that. What do you guys think?

that looks far superior to the first one, keep up the good work and learning process !!!!
Alright, I said I was going to make a tutorial for anyone interested after I worked up the second set of arms. I have finalized measurements with these arms and have made a set that are mirror images of one another to within 1/32th of an inch. Immeasurable with a tape measure and probably about as close as you can hope to get without complicated and expensive measuring equipment. Hell, that's probably about as close as these old mild steel frames are now a days anyway...

These measurements are for reference andeEstimating material costs only. Nothing is absolute and these measurements are no exception.

First, lets start off with materials. I've already mentioned some of the supplies already but I'm going to compile a list of materials and tools needed. Obviously this isn't a complete list but some tool and stuff are assumed you'll have if you're going to undertake this project...

Chrome-moly tubing:

8 feet of 1" x .083" x .834" tube
5 feet of 3/4" x .065" x .620" tube
1 foot of .125" x 4" sheet
1 foot of 1 1/2" x .120" x 1.260" tube
3 feet of 5/8" x .156" by .313"

Second, tools. This isn't an absolute list of things required just an idea.

8.8mm drill
5mm drill
M6 x 1.0 tap
M10 x 1.25 tap
M10L x 1.25 tap
M16 X 1.50 tap
belt sander
grinder with cutting disc in it
hacksaw (a portaband is better but a metal cutting bandsaw is best)
Mig welder with ER70S-6 wire (although 1bad442 recommends a Tig)

So once you've got most of the stuff to make the arms with handy, you can start cutting pieces.

The pivot tubes for the upper and lower arms are cut out of the 1" tube. The lower tubes are 1.925" and the upper tubes is 6.810". 4 lower tubes and 2 upper.

The 3/8" round rod needs to be cut into 3/8" long pieces to make grease fitting bungs. It's easier to weld and drill the bungs while the pivot tubes are out of everything because if something goes wrong it's easy to fix now, difficult to repair later. The bung needs to be welded 5/8" from one end of the bottom pivot tubes to make sure it sits into the grease fitting relief cut on the frame. The bung can be welded about 2" from one end of the upper tubes. That measurement isn't as critical because there aren't any cutouts for the upper grease fittings as long as you can get a grease gun on the zerk fitting.

Go ahead and and use the 5mm drill bit to drill through the bung while you can easily replace it. If you mess up the centering and bust out of the side of the bung, it's a lot easier to replace now and VERY difficult later. Once the holes are drilled, take a flat file and hit the top of the bung to smooth it out for later.
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I have to say your fab skills are excellant. I would love to have your jig and some cut tubes to tig a set together. I honestly pay my bills by being a welder but i do lack the skill in fabrication areas that you seem to have a good handle on. These a arms took a ton of thinking. Rep for you my friend!
man, would love to see a set of these finished up. i may be interested in a set.
When my son doesn't have the flu, I'm going to finish the tutorial and give every dimension and measurement and technique I've got away for free.

Between defending against onslaughts against my equipment, my welding skills, and my general attitude towards manufacturing and sales AND dealing with my screaming son, I haven't had time to finish this. I have all of the measurements on my clipboard but don't have the time or energy to translate and type it all. Maybe tomorrow.

Edit: sorry for that, but a little venting is in order and I cannot do it directly without getting banned off this forum permanently and that won't help anyone.
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It doesn't show when I started on a post, only when I finished... I started that last part about 4pm and that's how far I got.

Let's try this anyway...

The 1.5" tubing needs to cut into thin slices to make the ring to hold the upper ball joints. The thickness needs to be just a touch under 12mm. This is where the metal cutting bandsaw comes in handy because you need about 11.90mm not 11.5mm and not 12.01mm. My set of arms, I used a portaband and cut them really thick and then sanded them down with the belt sander which took be about an hour to do. If you can cut them straight and the right thickness, you can cut the sanding time to about 3 minutes just to straighten them up and thin them just under 12mm. Also, the tubing spec'd is exactly the correct inside diameter for the ball joints so they won't fit down in them without some prep work. A little drum sander on a dremel tool to take about .010" - .015" out of the inside is plenty. Be very careful and slow about this. Too much taken out and the ball joint will be loose. Don't oblong or taper the hole, just remove a little material

If you contact Stellar machine and performance he'll sell you a ricky stator ball joint with a threaded bung to fit it. So you have the 6 pivot points with grease fitting bungs and the rings and threaded bungs you have the beginning and ending points for both the upper and lower arms.

The dimensions are as follows for each of the tubes leading towards the ending points. The measurements here are from the center of the tubing unless noted.

The back lower tube is cut at an angle of 24 degrees and is 14 5/8" long

The front lower tube is cut at an angle of 8 degrees and is 13 3/8" long

The back upper tube is 15" long and notched at a 90.

The front upper tube is 12 1/2" long and also notched at a 90.

The back upper tube is bent using a 3/4" conduit bender to an angle of 75 degrees starting 6 1/2" from the center of the notch and bending in towards the ring location. If I had the $3,000 for a tig welder, I'd also have the $1,000 for a proper tubing bender and wouldn't be using a conduit bender but guess what?! it worked... two sets of arms now bent and made jumping on a conduit bender.

If you've followed me so far, we have the beginning and ending points for the arms and tubes bent and cut to length to fit.

Now here's where things start to get abstract and difficult (^^^those parts are the easy ones so if I've lost you already, you're in trouble...)

I have the measurements and angles associated with the arms but without a jig or a REALLY abstract kind of mind it's going to be difficult to just hang it out there and go with it. I did and that's why my set of arms are as ugly as they are but it can be done.
The angle that the ring (upper ball joint mount) sits at relative to the pivot tube is about 23 degrees.

The lower ball joint threaded bung has to be at an angle of about 39 degrees relative to the lower pivot tubes.

The difference in angles is due to the upper ball joint having about 2 degrees less throw than the ricky stator ball joint and the knuckles have two different angle mounts. Those together equal 16 degrees off angle from each other.

Those measurements are made so that 20" front tires mounted on norman420 spindles with the camber dialed out to 0 degrees, with banshee shocks on the front (with the lower shock mounts at the positions to be stated later) will only allow the center of the frame to drag by compressing the bumpstops to about 1/4 of their original length.

I would think that considering my weight, I'm about the only person who can compress the bumpstops to 1/4 of their original size without casing a 100 foot jump (which we've already determined because I welded them with a Mig welder they would fly apart upon contact anyway) and I don't wish that upon anyone.

Anyway, I got 8 3/4" of suspension travel without joint bind by using those angles.

Using those angles, I have overall measurements for the length of the arms so that one can triangulate and make sure each piece of tubing is at the right angle and the right length.

The lower arm:

The front of the lower arm is 14 1/16" from the furtherest back point of the pivot tube to the very tip of the threaded bung (think of the "highest" of it and measure to that)

The back of the lower arm is 15 11/16" from the very back of the pivot tube to the very tip of the threaded bung.

The front of the upper arm is 13 7/16" from the back of the pivot tube to the very tip top of the ball joint ring.

The back of the upper arm is 14 5/8" inch from the back of the pivot tube to the very tip top of the ball joint ring.

Using those figures you can triangulate the length of the assemblies and make sure everything is the right size.

If I haven't thoroughly confused you, get ready for the real whopper, lower shock mounting position.