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TxBandit
05-13-2007, 08:50 PM
I've been working on this thing for a few months and here is where I was this morning. *Since then I've finished some of the welding, mounted the engine, radiator and put some paint on the rear a-arms.

http://s191.photobucket.com/albums/z187/TroysPiranha/

Troy

RickS.
05-13-2007, 09:38 PM
Hey Troy,
It looks great! *Not sure what you have in mind on your rear a arms though.
It won't work the way you have them now. Unless you plan on steering with the rear wheels?
Links front and rear might help?? *You know the short outer bearing tubes that you see on most other Piranha a arms? Thats what keeps the upright & wheel from going toe in and toe out when accelerating and stopping. *I added the extra links on mine, because the bearing tubes are kind of short and see a lot of force constantly working them back and forth. The links help to lessen the effect.

TxBandit
05-13-2007, 09:53 PM
You are correct Rick. *I'll use trailing links similar to what you've done. *I'll rely on those to keep the wheels pointed in the right direction. *The use of the heim joints on the wheel end will allow for camber adjustment and the trailing links will allow for toe adjustment. *I haven't made the links yet as I'm out of tubing, tube inserts and heim joints. *I also need to sketch up some brackets for the end that'll be near the seat. *

I've still got a long way to go. *I've been trying to get the main chassis done. *I'll probably move on to the rear suspension next and get it completed. *

Troy

RickS.
05-13-2007, 10:17 PM
I'm not sure how well that will work. Because now the link will see a huge compression force. With the standard a arms and added links the forces are distributed a little better.
I guess you will find out, it may be fine.

TxBandit
05-13-2007, 10:22 PM
What size tubing did you use on your links? *I'm planning on using 1"x.095 with 1/2" heim joints. *It'll be a while before it's running so I won't be able to report on the findings. *If it breaks I'll go a different route.

Troy

RickS.
05-14-2007, 10:40 AM
I used 7/8" x .120 with 5/8 female heims.
I don't think you will break them. you may just get some flexing.

tenaja
05-14-2007, 10:48 AM
The 1" will be less likely to flex.

TutTech
05-14-2007, 11:19 AM
Looking good Troy.
Looks like your doing some really nice work.
Keep it up and ya on some projects you just never know until you
try them.

But when that day comes keep us posted and remember when you build your own car it just means you know how to fix it if it does brake.

Anyways off to a great start and looking good... now go get more metal and get busy on it we want to see it done.


[smilie=biggrin.gif]

Desertkarts
05-14-2007, 02:06 PM
Yep, a trailing link will force the rear to steer. You have A-arms that will swing on an arch.an the trailing link will need to swing on a different plane. It is sure to bind. Build a link and tack weld it into place. Put the car on stands, remove the wheel, and cycle your suspension. Let us know what happens. At a glance I would build a new lower arm with 2 heims. *Nice and wide. Looks more like an "H". Pick up the bearing carrier at 3 points 1 upper 2 lower.

Ricks diagonal link must pick up (connect to) the chassis "on plane" with the A-arms.

One other solution is to build one more "tie rod" that connects the frame to a "steering arm" on plane with the arms. The tie rod must parallel the arms or you will get bump steer in the back. I hope this is clear.

TxBandit
05-14-2007, 07:53 PM
Thanks for all the input.

I knew that the trailing link would force the rear wheels to change toe as the suspension cycled. *How much change is something I do not know. *I understand that zero change would be optimum, but how much is acceptable? *I also know that a small mount of toe in in the rear will help stabilize the car, this probably is only apparent in high speed situations, again, I have no idea how it will affect the handling of this thing.

Keep in mind that I'll be using this as something to run around in the woods with, maybe a trip to LS and occasional blast across a grassy field.

Troy

TxBandit
05-14-2007, 08:02 PM
If I rebuild the lower a-arm, I can get 4 3/8" spacing where the heims would mount at the bottom of the rear upright. *Is this enough? *Also, if I go this route will it completely eliminate the need for any other device which would keep the wheel pointed straight?

Troy

tenaja
05-14-2007, 08:21 PM
That's pretty narrow, but would be enough if everything is stout enough. The tire is like a big lever, so the farther apart your supports are, the stronger the system.

If you do that, then yes, it takes care of all toe functions on the rear tire.

Desertkarts
05-14-2007, 08:24 PM
If I rebuild the lower a-arm, I can get 4 3/8" spacing where the heims would mount at the bottom of the rear upright. *Is this enough? *Also, if I go this route will it completely eliminate the need for any other device which would keep the wheel pointed straight?

Troy

Troy, If you rebuild the lower arm just make sure the rim still fits. If you use heims you can add toe. It will also divide the load over two heims provided the shock is connected to the lower arm.

TxBandit
05-14-2007, 08:52 PM
I went out to the garage, pulled up a chair and stared at it.....and thought.....

I have enough "know how" and parts aren't really that expensive......I'm going to build both, the trailing link as originally planned AND I'll make another set of rear lower control arms using two heims spreading them out as much as I can. *It'll be a while before it runs, but when that time comes I'll have the parts to conduct a good field study and determine what I like best and if there is any noticable difference between the two systems.

Thanks again!!

Troy

RickS.
05-14-2007, 09:26 PM
My link is not on plane with either arm and there is no bind. The way I would describe it is that it's on the axis of the theoretical pivot point thats created by the double a arm geometry. The double a arm geometry actually simulates an arc thats center usually falls somewhere between your upper and lower inner a arm mounts. The further out you mount your trailing link on your carrier the further out the axis moves. If you mount it high the axis raises. mount low and it lowers. I track this arc in a rear 2d autocad view. You track this point after you settle on the link connection point to the carrier. If you decide to move the connecting point you have to retrack it again.
Once you create the arc, and find the axis, the forward end of your link is placed on the axis anywhere you want front to rear on the chassis. you could even mount one forward and one rearward. The Odyssey that you posted the picture of has the link on the rear. Hope this helps.

TxBandit
05-14-2007, 10:02 PM
Thanks for the explanation Rick. *After reading your post, laying out some arcs.....re-reading the post and laying out more arcs.....I've got what I believe is correct. *I still need material, but I've come up with something that appears to be correct on paper. *As soon as I get this done (next weekend) I'll report my findings.

Troy

Desertkarts
05-14-2007, 10:53 PM
My link is not on plane with either arm and there is no bind. The way I would describe it is that it's on the axis of the theoretical pivot point thats created by the double a arm geometry. The double a arm geometry actually simulates an arc thats center usually falls somewhere between your upper and lower inner a arm mounts. The further out you mount your trailing link on your carrier the further out the axis moves. If you mount it high the axis raises. mount low and it lowers. I track this arc in a rear 2d autocad view. You track this point after you settle on the link connection point to the carrier. If you decide to move the connecting point you have to retrack it again.
Once you create the arc, and find the axis, the forward end of your link is placed on the axis anywhere you want front to rear on the chassis. you could even mount one forward and one rearward. The Odyssey that you posted the picture of has the link on the rear. Hope this helps.

My bad. At a glance (in the edge photo group) it looked like it had all of the characteristics of a misaligned tie rod that would cause bump steer on a front suspension. It seems like it would load the carrier and either flex the link or compress the bushings causing some rear steering. The link on the Odyssey I understand. Yours I would have to cycle to appreciate.

Nice looking car!

RickS.
05-15-2007, 05:41 AM
Yes, It does look like it would bind, but as long as you find and mount on the axis there is none. I also track the cv stars and play with the geometry to minimize the plunge on the cv's. thats why you don't see a deep cup on my cv flanges. I don't need it because the star stays in the center to slightly outboard in the cv housing throughout the travel.

TxBandit
05-18-2007, 09:29 PM
I had a day off today so I ran around town picking up more parts. *I now have enough pieces to start making the trailing links. *After much thought I believe that with proper placement on the chassis end (as Rick described a few posts up) the trailing links will be what I am most happy with. *Unfortunately I have to go to work tomorrow and I'm not sure I'll have time to work on the buggy. *Maybe I'lll have some time on Sunday. *Whatever happens I'll take more photos of how the arrangment of all this ends up. *I''m ready to be finished with the rear suspension and move on to other areas as my goal is to have a "roller" possibly by the end of next week.

Troy

TxBandit
05-28-2007, 06:06 PM
I've added a few pictures to the album. *I went forwad with the trailing links and overall I'm pleased with the results. *I missed the "exact" mounting point just a hair and the result is a VERY small amount of bump steer at full droop and full bump. *I don't think this will have any noticeable effects with the type of riding I'll be doing. *I'm shopping for shocks at this time as well. *I'm leaning towards Fox 2.0's. *I should probably not tell you all that I mounted the rack upside down and now when you turn the wheel right, the tires turn left!! *WHOOPS!!! *I'll get that straightened out this week. *It's coming along slowly but surely.

Troy

TxBandit
06-10-2007, 08:33 PM
Today I started assembling the rear center axle and installing the CV axles. I completely dis-assembled the CV's, cleaned them thoroughly and re-assembled them with new grease and new boots. Overall, pretty easy. I installed all of the components in the center axle housing, welded the flanges to the stub axles and installed them. After I had one of the CV axles installed I started studying what I had done because it seamed that the CV's were binding WAY before full droop. It appears that I have assembled the eccentric adjusters upside down. This forced the center axle up higher than it should be therefore increasing the angle of the axle. I'll pull it all apart tomorrow and install everything correctly. I'm learning as I go!!

Saturday a friend of mine and myself took our Odyssey's out for a while. *It's been about a year since I had taken the Odyssey out and I forgot how much fun these things are!! We only rode for a couple of hours, but it was still a lot of fun. I lost a few bolts causing the starter to have problems engaging so I'll have to repair that sometime this week.

Troy