Prerunner RC Build

[NickRummy]

it's gotta be just about safe to say that this will be one unique ass RC truck. what are you planning on doing for the rear?

I've been reading up on suspension setups and I think I'll be doing a 4-link. The lower links will be like trailing arms that I'll mount the shocks to. I have to work out a way to get the links on the outside of the frame far enough to clear the shocks but other than that I think it will work out pretty easy.

After I get this steering sorted I'm going to make some body mounts so that I can finalize where the body will mount on the frame. Then I can set the rear axle in place and get it mounted and get this thing at least rolling under it's own power.

 

[NickRummy]

Nothing too exciting with this update for you guys but to me this was a big headache to conquer!

I made some new links and rearranged the mounting points. The idea WILL work for sure but I need to have the drop brackets machined or find something else I can modify. My tolerances just aren't good enough to keep slop out of the steering.

Also, the outside tire turns in pretty tight (as much as the knuckle allows) but the inside tire only turns about %60 of what it could turn. Off the top of my head I think it's because my cross link is too long. If I shorten it up it will push this inside tire out more and bring the outside tire in. I just need to find the sweet spot where it moves each knuckle lock to lock. I'll have to mess with the steering links too as this would throw off the toe.

At least I know I'm on the right track and it's fine details to make it work well!

Ride height with cross link added

Full bump. You can see on the passenger side there is some slight contact with the other link. I think I can move the chassis mounts up on the chassis a bit to get some more clearance.

The drop out. Geometry stays aligned perfectly!

 

[NickRummy]

Can any of you give me some info or a link to info on setting up the steering on a truck with this setup? Normally you want the inside tire on a turn to be turned in sharper than the outside but I'm finding it near possible to get that to happen with my setup. Mainly because as the drop bracket pushes the inside wheel it starts to travel up in its rotation which starts to shorten the distance the steering knuckle travels. Opposite happens with the outside tire. As the bracket rotates it moves up which pulls the outside tire in even more.

So what happens is my outside tire pulls in a lot faster than the inside and when the outside tire hits it's limit the inside tire still has a lot more rotation it needs to go.

I could probably got to chassis brackets that rotate horizontally with the chassis but I know this setup I'm working on now works because that's what is used on the real trucks.

 

[Tee Rev]

Look up Ackerman steering

 

[NickRummy]

Look up Ackerman steering

Yeh, most of what I've read is for a normal steering setup with the cross link running from knuckle to knuckle. Not with the cross link up on the frame. I'll read up on it here and there.

I got the body mounts made last night and got the body, interior and rear fenders located. No I know what length to make the trailing arm and upper links so I'm going to do some drawing today.

 

[CopyKat]

Ackerman Angle.

Just at a quick glance what you have going on is that the arms need to be Perpendicular to the ground at ride height. From there the offset distance from the frame and how long the arm is will determine the angle. Dont strive to get it 100% correct. even if it's a little bit it will help.

 

[NickRummy]

Ackerman Angle.

Just at a quick glance what you have going on is that the arms need to be Perpendicular to the ground at ride height. From there the offset distance from the frame and how long the arm is will determine the angle. Dont strive to get it 100% correct. even if it's a little bit it will help.

Are you referring to the beams being perpendicular to the ground or the steering links?

 

[NickRummy]

Ok what do you guys think about this lower link setup? Is it normal to just run the upper links from the center of the axle to the same point the trailing arms attach to the chassis but on the inside?

Specs are as follows:

- shock length extended 6.36" (47.75" to scale)
- shock length compressed 4.09" (30.7" to scale)
- Lower link length 8" eye to eye (60" to scale)

Here's sitting at ride height.

Here's the bump which is about 1.13" (8.5" to scale) of up travel. I don't think I'll get much more than this because the axle will hit the frame.

Here's the down travel. Drops out about 3.33" (25" to scale). So overall it has around 33.5" of travel. I'm curious to see what you guys think about the up travel and down travel ratio. also curious to see what you guys think about the upper shock mount placement.

 

[NickRummy]

I got the stock rear fenders cut out. Ready to start building them up into a mold for some flared fenders. Also put together a mock up set of trailing arms.

 

[freeride]

i like the idea of building a prerunner in my living room or on the kitchen table. looking good

 

[NickRummy]

Tell me what you guys think about this setup. Here's a top view looking down on the rear end with the trailing arms. Chassis mount is right under the frame just like the mount for the front radius arm. Think this should be good?

 

[CopyKat]

I get Red X's

 

[NickRummy]

Here's the direct links

http://i736.photobucket.com/albums/xx1/rcworld2/Ranger Prerunner/trailing_arm_layout.jpg

http://i736.photobucket.com/albums/xx1/rcworld2/Ranger Prerunner/trailing_arm_layout_side.jpg

 

[CopyKat]

Red X's again.

 

[BlackBII]

Red X's again.

Working for me.