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UTV's Off Road ( RZR, YXZ, Mini Buggy, Carts,etc.) => UTV Chassis and Suspension => Topic started by: ironknot on November 16, 2012, 08:55:07 PM
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[smg id=1494]
http://www.dtsfab.com/index/MGalleryItem.php?id=1494 (http://www.dtsfab.com/index/MGalleryItem.php?id=1494)
This is what happens when you stick with an idea too long. . . or just long enough.
Please tell me what you think.
The rear spool idea is a double single sprocket about 1 3/4 wide machined with six threaded holes and recess on both sides for plunge. 4.25 large thin section bearings on cv.
38 inch axles with bearings on cvs mounted in plate for hub and then double sheard mounts top and bottom 200mm apart and offset 68 mm front to back to match A-arm mounts 20 degrees offset.
Spool to jack, 1.38 jack with double single sprocket on brass bush in centre. Jack sprocket has slots and holes for nylon rod then slot then nylon rod, two of these top and bottom with holes for nylon rod going through from side to side and slot connecting hole about 1/2 inch deep: Coupler on both sides of jack sprocket with 1/2 pins (grub strews 1 1/2 long) sticking out 1/2 inch with thread machined off. Pins into slots, two slots a side four in total for flex drive.
Think I may have over cooked this one but it makes sense to me.
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for some reason i can't view the pic or file attached to the post?
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Issues.
As viewed from the side, the tire will move in an arc as it goes up and down due to the angle of the A-arm mounts. Anything past level on the arms and the tire will actually start to move forward. This does not work well. Your wheel path should always move to the rear. You could angle the arms mounts as viewed from the side a little to negate this.
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Fixed pix I think and this is the side view.
<img src="http://www.dtsfab.com/index/MGalleryItem.php?id=1495" alt="" />
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Fast's car is set up somewhat like this. His rear arms are back a bit further as mentioned above. Results in axle being run through arms. Maybe he can chime in.
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Have you priced the bearings and long axles yet? If I understand this correct you are ,in effect,building your own midboard hubs.
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Axles are around 580 and I just found the listing for the bearings. I wouldn't say its going anywhere yet, but I've been slowly getting things inorder.
The midboard with inboard brakes seems like a lot of guess work. I've got RCV's so I'll make a move on the bearings next. Could be a waste of time but I'm in not hurray and want the best I can come up with regarless of the way that it takes me.
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Fast's car is set up somewhat like this. His rear arms are back a bit further as mentioned above. Results in axle being run through arms. Maybe he can chime in.
Completely different ball of wax. Mine is a five link and they swing the tire in a in and out movement rather then a front to back movement. Most all trailing arm car's will pull the tire front to back some. Can't see that it can hurt anything. Don't see why his design will not work.
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5 link or 6 link are totally diff and like fast said plus wheel base does increase and decrease with lateral links as well too. I kind of like the design and the first pic would need the carriers welded at the end to be trued up so there wasn't an extreme angle on the cv or any left to right but the arc of the swing will be interesting to see how that works out. like bdwk said past parallel you will loose wheel base, not a horrible thing it will just make it an interesting design to bring to life. I think it's doable just have to try it. the first pic reminds me of the flux capacitor out of the delorian off back to the future lol. i like it though.
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Axles are around 580 and I just found the listing for the bearings. I wouldn't say its going anywhere yet, but I've been slowly getting things inorder.
The midboard with inboard brakes seems like a lot of guess work. I've got RCV's so I'll make a move on the bearings next. Could be a waste of time but I'm in not hurray and want the best I can come up with regarless of the way that it takes me.
I was just curious. Seems like you are aware of the cost and willing to proceed. In general the idea is sound IMO.
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I do agree that bdkw is correct about not wanting foreward movement of the arms. However the amount will be minimal. Try to tweak the design to bring it to an absolute minimum.
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Fixed pix I think and this is the side view.
(https://dtsfab.com/proxy.php?request=http%3A%2F%2Fwww.dtsfab.com%2Findex%2FMGalleryItem.php%3Fid%3D1495&hash=85b7b5444f323fcf36f4cf1a383eef8a13f2ccfd) (http://www.dtsfab.com/index/MGalleryItem.php?id=1495)
Ah, that makes more sense. That should be just fine.
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Simpler, lighter, stronger.
(https://dtsfab.com/proxy.php?request=http%3A%2F%2Fi55.photobucket.com%2Falbums%2Fg122%2Fbdkw1%2FA-Trailling4.jpg&hash=74079105a254448163274096eec98602d0c64310)
I would also redo the X brace in the B-pillar. Some diagonals from the top link mounts to the center of the floor bar, then an X brace from those to the upper corners on the hoop. But that's just Me......
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If it has camber change as it cycles it will also have toe change.
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Simpler, lighter, stronger.
(https://dtsfab.com/proxy.php?request=http%3A%2F%2Fi55.photobucket.com%2Falbums%2Fg122%2Fbdkw1%2FA-Trailling4.jpg&hash=74079105a254448163274096eec98602d0c64310)
I would also redo the X brace in the B-pillar. Some diagonals from the top link mounts to the center of the floor bar, then an X brace from those to the upper corners on the hoop. But that's just Me......
Thanx Bdkw1, the front is long for a fuel tank infront of the pedal box and as the rear assembly has just come up so its a bit of a mess. Might take a good while to get some parts and start measuring. Everything is relient on something else its a jigsaw starting with the spool cv distance so I'll start with those parts and if that works move from there.
I post the progress down the track a bit.
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If it has camber change as it cycles it will also have toe change.
Only on a trailing arm car. A-arms not afflicted this way.
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It needs a lot of tuning, I should explain the original idea was for a 5 link design and I was working on the driven line to get the maximum amount of travel. Now with the double single sprocket I could maybe put the cvs bolted to it so the forward link, Hub into chassis wouldn't fit how I wanted it so this is the solution. Its hot of the bendtech by a couple of days and I was wondering if it was as practical as it seems and by the sounds of it, might be the answer.
I have Grey Area 4 piston/Combo front brakes/hubs, 2 x 16 fox 3 tube by-pass, 2 x 16 fox air, 2 x 18 fox res coil overs, RCS with 300m stars, budgeting for welder, thinking small tig. Then learn how to weld, have some experience and doing night course in the new year. Hopefully by the time I'm welding Ok I'll have the design workable
Not in any hurray I'd rather get things the way i want than have some thing tomorrow.
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Only on a trailing arm car. A-arms not afflicted this way.
I haven't taken time to think that through but are you sure about that with this idea? This isn't a regular a arm geometry is it? If it were there would not be any wheelbase change when cycled through the range of travel. Since there will be a wheelbase change would there not be a toe change ? Just talking without thinking this through.
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Thanx Bdkw1, the front is long for a fuel tank infront of the pedal box and as the rear assembly has just come up so its a bit of a mess. Might take a good while to get some parts and start measuring. Everything is relient on something else its a jigsaw starting with the spool cv distance so I'll start with those parts and if that works move from there.
I post the progress down the track a bit.
Just a suggestion that will help prevent issues later,build from the wheels in. Everything really revolves around that . First step of any build is to determine the wheelbase and track dimensions.EVERYTHING is dependent on those 2 things and cannot be compromised.
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Also curious as to why you are considering using a double single sprocket.
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with the arc they will be pivoting on I don't think there will be a toe change if it's done right but if it's a true daully and has a tie rod getting the bump out could be trying!
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The arm mounts are not parallel to the cars centerline. If they were I'd agree but they are skewed. Honestly,CAD would prove whatever is correct and at this time I feel we only have WAG's.
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Double single sprocket should give the strength I'll need for a reduction from cs to jack. Width 86 inches wheels base 118 inches. Also need to determine the mounting face/centre cv distance because the A-arm mounts will have to be inline to eliminate plunge.
Not a new idea: http://www.offroadfabnet.com/forums/showthread.php?t=10011 (http://www.offroadfabnet.com/forums/showthread.php?t=10011)
Have looked at this idea a while ago and the theory is good. Toe variation is a percentage of the inlines a-arm. In-line 100 percent 45 degrees 50 percent as the toe variation will move the hub clock wise and anti clock wide viewed from the side. Or if this was a double trailing arm (two trailing arms) the toe would affect caster. That's it as the angle is moved from the inline position the toe starts affecting castor.
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Also, you either need to move the roof bars out where they meet the B-pillar or move the rear diagonals in. They should meet at the same spot on the B-pillar.
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Thanx Bdkw1 I should have checked a few precidents but I liked the look of it, I'm going to submit the plans to Cams (Australian Motorsport governing body) before I start.
What I want to know is what is the ideal diamensions for a single buggy if Im left with an 86 inch outside rear wheel measurement. 112 seems popular for smaller buggies and would give a better turning circle but I really want to be able to hold top speeds over whoops and 118 seems like the next step and would give me a bit more straightline stability. 26
If your have a theory I'd like to hear it and spec on suspension travel would be very welcome I'm thinking if the back comes together I could get 26 inches of wheel travel (with MT Baja belted 31 inch) sounds huge but I shooting for the sky. Preload anyone? Another guess 8 inches. . . thoughts pls.
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ride height ,IMO,should be 1/2-2/3 of travel depending on a lot of things not the least of which is just plain personal preference
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I'm going to submit the plans to Cams (Australian Motorsport governing body) before I start.
They will actually review plans and OK them before being built? What a strange concept........... rofl
That was a joke that would only make sense if you had run a car through SCORE tech.......
As for wheel travel, Is this for NZ tracks or Ausi tracks? Either way 26" is way too much. A well done 16" would handle either. 12-14" would be better in NZ.
Also, fuel tank in front? On a light car this will create a lot of weight bias change from full to empty. Getting mounted near the center of the car would be the best. I'm all for weight in the front of the car, but it needs to be something that doesn't change like the battery.......
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Buggies for Aussie and the suspension numbers are a matter of casing an idea for a very long time. Its the 26 inches is too much that I want to work out, like how much is too much pre-load.
Class one buggies and some TT are using 24 inches front suspension, maybe that's the magic figure I'm after even with smaller wheels the centre of gravity is still the same after preload and too much preload will make for huge body role and pitching into corners and maybe whoops.
I had an old Type 4 vw and I remember with a full tank of fuel it was impossible not to get a big off putting dip in the front end braking into a hard corner. So move the driver forward and put the tank behind the driver as low as is possible.
Still having trouble with the too much suspension and preload idea, lol LMAO LMAO, its an unexpected change of perspective I'm going to do some more research from this new perspective and see what were I get. I could probably put a rear sway bar but I think a front sway bar would be out of my league.
So if you have an idea of the ideal amount of pre-load or just care to tell me what you reckon, I'd appreciate any ideas.
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preload IS ride height.
ride height ,IMO,should be 1/2-2/3 of travel depending on a lot of things not the least of which is just plain personal preference regardless of travel . Trophy trucks and small buggies are 2 completely different animals. A big and heavy TT needs a huge amount of travel. A light buggy will not likely even be able to cycle the suspension through 24" or more travel. To do so would require a very soft valved shock. That soft valving will do almost nothing to control the car through whoops and the body roll would be horrendous. If massive jumps are the only thing you would do then MAYBE a smaller,lighter buggy could use huge travel numbers. Don't get tunnel vision when it comes to numbers. As BDKW said,sometimes less is better.
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For something fun.....
A class 1 buggy weighs 3500-4000#'s. Lets say 3750 average. They usually have around 20" of wheel travel. say 40/60 weight bias and you get 1500#'s in the front. 1500/20 inches of travel=75#'s per inch. Now if your motorcycle powered car weighs 1500#'s with the same weight distribution you get 600#'s in the front /75 = 8" of travel. I could make the 1500# car handle the same with under 10" of wheel travel.........
More mass needs more time to decelerate transfer the same amount of force. Wheel travel = time. The lighter the car the less wheel travel is needed. Granted, this assumes that a lot of things like unsprung weight will decrease proportionally so it's not exact but more of a fun observation.
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What a great way to explain it. 8)
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For something fun.....
A class 1 buggy weighs 3500-4000#'s. Lets say 3750 average. They usually have around 20" of wheel travel. say 40/60 weight bias and you get 1500#'s in the front. 1500/20 inches of travel=75#'s per inch. Now if your motorcycle powered car weighs 1500#'s with the same weight distribution you get 600#'s in the front /75 = 8" of travel. I could make the 1500# car handle the same with under 10" of wheel travel.........
More mass needs more time to decelerate transfer the same amount of force. Wheel travel = time. The lighter the car the less wheel travel is needed. Granted, this assumes that a lot of things like unsprung weight will decrease proportionally so it's not exact but more of a fun observation.
Wow, very insightful. About 5 / 6 years ago I asked the question on another forum and got crickets. My question was is a well thought out 12" better than a poorly thought out 16" or some variation of that. My underlying concern being that so many folks had tunnel vision re: Total travel vs. Quality of Travel. You just kind of hit the nail on the head.
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He sure did!
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Wow, very insightful. About 5 / 6 years ago I asked the question on another forum and got crickets. My question was is a well thought out 12" better than a poorly thought out 16" or some variation of that. My underlying concern being that so many folks had tunnel vision re: Total travel vs. Quality of Travel. You just kind of hit the nail on the head.
Are we still talking about suspension? Or something else rofl
So I'm trying to soak this in, and seems to me that any type of suspension that has a forward arm (trailing, semi trailing, 4/5/6 link) that once that forward arm reaches level any additional up travel will result in the tire also moving toward the front of car. And if your running 30" tire and 3" ground clearance then 30"/2=15"-3"=12" so the last 12" of travel the tire would move forward.
And thats a sweet example of the wheel travel vs weight.
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So I'm trying to soak this in, and seems to me that any type of suspension that has a forward arm (trailing, semi trailing, 4/5/6 link) that once that forward arm reaches level any additional up travel will result in the tire also moving toward the front of car. And if your running 30" tire and 3" ground clearance then 30"/2=15"-3"=12" so the last 12" of travel the tire would move forward.
And thats a sweet example of the wheel travel vs weight.
Wheel moving forward toward the chassis pivot line but back at the angle the pivots are angles up at the front. I thing the bump is at about 16 degress so if the pivots are angled up at the front more than that its still moving back.
I'm working out why sometimes these ideas move more slowly than others, but I think I've got it.
Next question; would the wheell moving back make that much of a difference maybe comparing it to wheel size. With the wheel moving out from the below holizontal and back at the (umm) pivot angle the combines effect from hitting a bump and the wheel moving would be a big combines rearward movement that could smooth things out.
If the approach angle of a bump is 40 degrees and the initial movement of the wheel is 20 degrees back does that back the effective face of the bump 20 degrees compared to an a-arm design. This is an oldy, but a goody.
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Opinion only as I have no way to prove it. The question you pose has a time component that would be involved. At slow speeds it is irrelevant. At high speeds it could become a factor. Just an opinion.
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Bit off topic but along the lines of what we're talking about, found this pdf with some interesting observations on G-forces at impact, time and the use of suspension:
www.highspeedcraft.org/pdf/7Ullman_HSC_Suspension_Seat_Design.pdf (http://www.highspeedcraft.org/pdf/7Ullman_HSC_Suspension_Seat_Design.pdf)
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Still not impress, the Shamwow chassis got it all.
How about a limiting strap from the base of the hoop the top hub, a-arm mount to limit bump. Nylon donut between two washer mounting the clevis and the shamwow's got limiting bump stops.
Did you say grill, of course you can.
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Running rake in suspension is a good thing. It does take a lot of shock load out. This is why VW's work so well for what they are. Just be aware the rake win the front will cause more dive in braking. Either stiffen up the springs and live with it or dial in a little anti-dive......
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uh,oh,the anti-dive subject again.....................where's xxxxx? He'll argue 180 opposite. Personally I see no harm in anti-dive but others don't see it that way.
(xxxxx? I decided it wasn't a good idea to use his name without his permission) :)
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Bit off topic but along the lines of what we're talking about, found this pdf with some interesting observations on G-forces at impact, time and the use of suspension:
www.highspeedcraft.org/pdf/7Ullman_HSC_Suspension_Seat_Design.pdf (http://www.highspeedcraft.org/pdf/7Ullman_HSC_Suspension_Seat_Design.pdf)
I just read this. Those boat seats would be the cat's ass in a monster truck or anything with enough room.
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I think I can live with the dive as the move in alignment for the front suspension tabs would loose the wheel moving backward through the suspension movement as I understand it.
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Wheel moving forward toward the chassis pivot line but back at the angle the pivots are angles up at the front. I thing the bump is at about 16 degress so if the pivots are angled up at the front more than that its still moving back.
I'm working out why sometimes these ideas move more slowly than others, but I think I've got it.
Next question; would the wheell moving back make that much of a difference maybe comparing it to wheel size. With the wheel moving out from the below holizontal and back at the (umm) pivot angle the combines effect from hitting a bump and the wheel moving would be a big combines rearward movement that could smooth things out.
If the approach angle of a bump is 40 degrees and the initial movement of the wheel is 20 degrees back does that back the effective face of the bump 20 degrees compared to an a-arm design. This is an oldy, but a goody.
I think that it really depends where in the travel the wheel moves forward. On a 5-link or trailing arm the wheel moves forward at the very bottom of the stroke. At that point it doesn't matter because the impact of an edge is already taken care of and if you reach the very bottom of the travel then you are absorbing a major vertical hit.
People get away with this A-arm design (non-parallel to the center of the car) on the front all the time. The wheels travel forward as they bump up from ride height, so it either really doesn't matter that much, or in the sand the conditions aren't that punishing. IMO.
Throwing some anti-dive into this design would be great. ;D
I can't believe Fabr is the only one that sees the toe consequences of A-arms non-parallel to the center line of the car. Toe change is inevitable with any camber change.
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I'm in the minority many times. rofl ;D ;D So was Columbus. ;)
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I don't think toe will be a factor because the mounts on the hub are at the same angle as the mounts on the chassis. This the inner and outer mounts parallel, the centre point, top and bottom of the hub are moving straight up/down and not affecting the toe in any way.
If the mounts at the hub were in-line with the centre line of the buggy, or the line of the hub, the toe would change dramatically as the suspension cycled.
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Have you put this to CAD? If not ,all we're doing is opinionating and best guessing.
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If you have camber change you will have toe change. You will also have bind if your pivot isn't parallel to your mounts. The only way around this is to run a tie rod and hiems.