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H&M

Motorider

Well-Known Member
I got this picture off the H&M website, it is a longtravel kit for the a-arm rangers, and I wanted to know how they are able to get the throw on the uniballs, when they are mounted this way. It would seem to me that you wouldn't be able to turn very tightly? Anyone know about this design?

thanks
 

JOSH

Well-Known Member
GOOD QUESTION, I WOULD LIKE TO KNOW THE ANSWER TO THAT ONE
 

firedog

Well-Known Member
From what I know there are trucks running similar setups, ATS class 7 toy to name one of them. The advantages that you get from increased wheel travel by mounting the heim(s) vertically may sway some people into a little bit less steering. I'm not sure exactly how many degres of movement are in the heim(s) but I know it's quite a bit. I wouldn't think that you are sacrificing that much steering. Just my .02
 

BradM

Well-Known Member
The reason that they can do it that way is basically because they use a spherical plain bearing (uniball) that is substantially oversized for the application. Then they make or buy reducing spacers that are machined to reduce the bolt diameter and neck down the outside diameter in order to allow the ball to rotate farther into the race. These spacers are sometimes referred to as high misalignment spacers for that reason. They increase the maximum allowable misalignment.

As previously stated, by locating the bearing in the vertical plane as shown, the spherical plain bearings no longer limit the suspension travel but rather they limit the maximum steering angle. For example, a 1" spherical plain bearing with a 3/4" fastener and the appropriate reducing spacers can handle over 25 degrees of angular misalignment in each direction. That may be adequate for some trucks. Otherwise, a larger bearing or smaller fastener selection can increase the allowable misalignment angle. If the bearings are located in the horizontal plane, the same reducing spacers are used to increase the total suspension travel.

There are several potential problems with that design. First, is obviously the potential limits of the steering angle. Also, it seems to me that in order to take full advantage of the maximum allowable steering angle the design would have to be without any ackerman steering effects since ackerman causes the inside wheel to turn farther than the outside wheel. I suppose that a compensation could be made by locating the bearings in the vertical plane but at an angle other than perpendicular to the frame. I haven't seen that done yet. Possibly the biggest problem with that concept (this applies to high misalignment spacers in any application) is that the contact surface area of the ball on the race is reduced at high angles. The bearings are designed and engineered for 100 percent contact area and the rated load carrying capabilities reflect that. A reduced contact area will reduce the capacity of the bearing under high angle usage. Another potential problem would be the increased opportunity for foreign matter (dirt) to enter or be forced into the bearing between the ball and the race. That would lead to increased wear if it occurred.

I will attempt to attach a picture and chart to illustrate the concept. Both are from product literature supplied by HM Engineering 714-979-6631.


"The only source of knowledge is experience." - Albert Einstein
 

Attachments

FABRICATOR

Well-Known Member
Motorider,
Didn't you know? This is in fashion right now!!! We went through this a few months ago here and there were some pictures then also. Except for the possibility of letting a bit more dirt in, as mentioned by BradM, about the only advantages are the maintaining of more usable bearing surface area throughout the travel than a vertical bolt setup and some travel advantage with short A-arms. Bearing size is of little consequence here because the unit is way oversized to begin with. Yes these balls wear out, but that's because of the movement not high pressure. The uniball could be a 4" unit and it would have a similar life span. It would likely be less due to the greatly increased surface speed. Limitations in wheel travel often come from steering components or geometry before limits of uniball angle. These setups are neat but don't go any faster.

<font color=orange>The best ideas are the ones that look obvious to the casual observer.</font color=orange>
 

sbro

Well-Known Member
On a daily driver seeing an occasional tight u-turn, what potential problems would surface from constant contact between the spacers and cup? Or if the cup comes in contact with the upper spindle mount first? Would it be a good idea to limit the steering angle?
 

ONEOF2

Member
Brad is correct on the angle of the ball being such that it allows full turning which this sustem gets full turning radius with the angles engineered in the arms.We spent alot of time cycling this system till it was exactly what we were looking for.
 

BradM

Well-Known Member
I didn't mean to imply that you couldn't achieve ackerman with this set up. Rather, I was suggesting that if ackerman was employed in the steering geometry and the bearings were perpendicular to the frame, the full allowable misalignment angle would only be used at the back side of the bearing. That is simply because ackerman requires that the inside wheel turn sharper than the outside wheel. Therefore, the bearings would not be utilized to their full capacity with respect to allowable misalignment angle. That would limit the maximum steering angle by a few degrees. However, as stated previously there are often other factors that limit the steering angles.

That could be corrected with some careful study of the geometry and a slight angular change in the location of the bearings with respect to the frame. Maybe it has been done. From what I saw of that truck at contingency in Laughlin, there were other design aspects that would concern me more than the steering angle.


"The only source of knowledge is experience." - Albert Einstein
 

Dave_G

Well-Known Member
Wow, I'm impressed. These guys and their uniballs just haven't figured it out yet. They need to take a look at the setup I built for the Duralast TT.....A uniball mounted in a 300m trunion that also pivots in a set of bearing blocks with aluminum bronze bushings. You get great angularity in any configuration through the stroke of travel and steering. I'm suprised that no ones caught on to this yet. It's a very reliable setup that has given them zero problems.

Dave

"I know it all, but I can't remember most of it..."
 

Dave_G

Well-Known Member
Re: Lets see some pics of what you are talking about.. :)

Hmmm.....don't think I have any pics of that stuff. When Enduro ( formerly Didntlast ) goes through tech/contigency at San Felipe or some of the other races you can probably get a good look at the setup there.

Dave

"I know it all, but I can't remember most of it..."
 

Kritter

Krittro Campbell
John

Gabby must be rollin deep now. Custom Built Wagon...where were you when I was growing up?..Oh yeah, I know where, bumpin "the posse's on broadway" in your yota! HAHA had to do it, couldn't resist.

Kris

Kris
<A target="_blank" HREF=http://www.csupomona.edu/~kjhernandez>My Web Page</A>
 

Waldo

Safehouse
Dude- How much travel does your wagon have. Do you have to change the valving of your shocks every couple of months because of your growing daughter? What about the rubber? Are you running Chevron muds or Red Rider A/T's?

BRAAAAAAAAP!
 

pciscott

Well-Known Member
If you use a large enough bearing you can get plenty of steering, but the main reason to use this set up is longevity. The spherical ball was made to work in this direction and you should not hit huge holes with your wheels turned or you will end up on your roof. The other thing that is nice about this setup is you can press a bearing into your upright much easier than a bulky A-arm you have to make special tooling to fit in your press. The trunion uniball setup that Dave is refering to is trick and you can definitely get more steering, but this setup probably costs double. With the uniballs Newline is using on our new prerunners you can get 34 degrees steering each way. Besides its good to have the biggest balls possible in offroad racing I am told!

God Bless America

Scott Steinberger Trophy Truck #7
 

ntsqd

Well-Known Member
Dave, that sounds similar to the front upper joint arrangement under the Herbst Truggy. It was hard to see exact geometry at the Expo with the tire in the way, but I remember looking at it and thinking "Duh !!!"
Perhaps the suspension design concepts of passenger cars pre-ball joint era should be looked at. We're coming back around to something like them.

TS

"Teach you all I know and you're still stupid"
-- Howdy Lee
 

drtdevil93

Well-Known Member
you should be able to get at least 60 degrees of angle change out of a uniball. that gives enough for steering.

erik
 
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