Proper Rear Trailing Arm Geometry
 

So, while I was swapping in a built SCX10 trans and SCX10 F9 Currie axle I decided I wanted proper rear trailing arm geometry.

That being said, simple bolt on brackets were out of the question as I felt they'd weaken the stock chassis too much with the extra holes, fabbing up mounts that used the existing holes seemed too ungainly, using an SCX10 modified chassis with custom front plate for the IFS was making it too heavy and more expensive...

Then I had my epiphany while going through my old Axial stock spare parts... I came across the stock AR60 axle link mounts and the idea to notch the TWH tub chassis and using a combo of epoxy and an automotive plastic repair kit along with a small bracket screwed in from the bottom of the chassis then into the back of each mount hit me.

Below are the mock-up images on the old throwaway tub... final version will be just two ar60 axle link mounts coming through the bottom rear of the chassis just outside of the stock molded lower trailing arm area.

The trailing arms will be attached to the bottom holes and upper links to the upper holes.https://uploads.tapatalk-cdn.com/201...01f64f59b1.jpghttps://uploads.tapatalk-cdn.com/201...e115e66b2c.jpghttps://uploads.tapatalk-cdn.com/201...f4f75df932.jpghttps://uploads.tapatalk-cdn.com/201...006802818f.jpghttps://uploads.tapatalk-cdn.com/201...da49c6315f.jpghttps://uploads.tapatalk-cdn.com/201...326f61e437.jpghttps://uploads.tapatalk-cdn.com/201...c24be413f7.jpghttps://uploads.tapatalk-cdn.com/201...3940218a59.jpg

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Re: Proper Rear Trailing Arm Geometry
 

I really like that green part for using the SCX10 gearbox. Where did you get it?

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Re: Proper Rear Trailing Arm Geometry
 

I got it on Shapeways.com, just search scx10 transmission mount.

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Re: Proper Rear Trailing Arm Geometry
 

Thanks

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Re: Proper Rear Trailing Arm Geometry
 

She is done, now for some test and tune...

That Tekin Pro4HD 3000kv motor is gonna make her run like hell.

She isn't meant to be pretty, more of a Mad Max build with parts from 5 different rigs, 4 of which are Axial rigs.

So the setup is thus;
Mirrored SCX10 metal geared trans
32p RR steel 56t spur
32p RR pinion
Shapeways SCX10 trans Twin Hammers mount
VP SCX10 F9 Currie rear axle
Modified Yeti trailing arms
Yeti 5" rear shocks
90mm front shocks
SCX10 rear shock hoops on the front
Twin Hammers front sway
Hot Racing Bomber front sway on rear
VP Wraith titanium upper links on rear
VP knuckles and chubs
Yeti MIP rear driveline
RC4WD driveline from trans to front diff
Helical cut front diff gears open diff with 120k wt. diff oil
Castle Momba Pro ESC
Tekin Pro4HD 3000kv motor
Custom fuel cell
Custom firewall
CNC Custom 1.9 deep dish wheels with LURC rings and scale hardware
Onetoomanyrcs front rock lights with Dragon Eyes covers
Onetoomanyrcs rear KOH light bar
RCTags custom license plates
Custom exhaust stacks
Wraith droop kit on front shock hoopshttps://uploads.tapatalk-cdn.com/201...9bcc629f3f.jpghttps://uploads.tapatalk-cdn.com/201...bdd0cad10c.jpghttps://uploads.tapatalk-cdn.com/201...6a67c1dfe4.jpghttps://uploads.tapatalk-cdn.com/201...203ce933cd.jpghttps://uploads.tapatalk-cdn.com/201...91f1dc087c.jpghttps://uploads.tapatalk-cdn.com/201...83a529b30b.jpghttps://uploads.tapatalk-cdn.com/201...21538745bb.jpghttps://uploads.tapatalk-cdn.com/201...df5291bc40.jpghttps://uploads.tapatalk-cdn.com/201...726dfd454d.jpghttps://uploads.tapatalk-cdn.com/201...7401ee2a03.jpghttps://uploads.tapatalk-cdn.com/201...e7f787888d.jpg

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Re: Proper Rear Trailing Arm Geometry
 

Looks great.

Re: Proper Rear Trailing Arm Geometry
 

So what was the issue with the stock trailing arm geometry?

Re: Proper Rear Trailing Arm Geometry
 

The stock geometry does not utilize the trailing arms, instead they are just fancy lower links.

Best comparison I can give is to look at the Yeti, Rock Rey and Bomber rear suspension.

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Re: Proper Rear Trailing Arm Geometry
 

I'll give you that logic; the angled trailing arms are not ideal but they are still acting as trailing arms. The shocks are still mounted halfway up the link and therefore have much more leverage on them than if they were mounted to the axle.

However, the shock angle you have now is pretty piss poor compared to stock. The best way to mount shocks with trailing arms is perpendicular to the link at full compression to get a decent rising leverage rate on the spring and dampening.

Re: Proper Rear Trailing Arm Geometry
 

Call them what you will in their stock form but, I have never seen a trailing arm on a 1:1 properly assembled where they mount that close to the center-line as the stock TWH TA's do.

Furthermore look at any competitive 1:1 or U4 rc rig out there and none of their TA's mount in close to center-line for a reason.

As far as shock angle goes I guess you missed the part where I needed to do a test n tune. The shock location on the arms is/was temporary until I could get it out and run it in its new configuration.

I am endlessly amazed at the argumentative and know-it-all attitudes of others who like to chime in on a project they have not built nor operated, let alone recognize it as a first for the Twin Hammers.



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Re: Proper Rear Trailing Arm Geometry
 

Did some testing today and will do some on the track later this week.

So far the rear shocks in the furthest rear mount location on the trailing arms work the best.

The weight distribution is damn near perfect on jumps.

I may put in a stiffer rear swaybar however or sand down the outside lugs a bit on my rear tires.

The Pro4HD 3000kv motor using a 56t 32p spur and 17t pinion are perfect. Lots of torque and more speed than any of the other 1.9 IFS rigs I'll be racing against.

The front open diff with 120k diff oil is dead on as well.

May give her a go at the next rick bounce event as well.

Ended up bobbing the rear chassis as I did originally too.

This little rig is one bad mamba jamba.

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Re: Proper Rear Trailing Arm Geometry
 

Looks like a great piece of work.
As i recently read - The wide spacing of the front of the lower links will raise the roll centre. Nice work.
The spacing of the front of the upper links looks very close to the lower. Does this not make it 'jack up' under acceleration?

Re: Proper Rear Trailing Arm Geometry
 

The rear upper links need to be a bit higher for sure but, I need to come up with a decent looking mod for that. I don't want to cut or drill into the tub chassis anymore than I have as it is not the strongest one I've seen.

Most likely I will build off of the new mounts using a plate on each side of each mount and space the upper link mount location up a bit higher... I'll probably use the measurements from the Yeti scaled down for this truck.

On acceleration it lifts the front right tire and doesn't squat as much in the rear as it should due to the upper links mounting location so close to the trailing arms' mounting location.

However, on jumps and rocks the rear soaks up the punishment.

Trying to keep with the stock chassis and get this 100% is a test for sure. LOL



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Re: Proper Rear Trailing Arm Geometry
 

FYI I am using a SCX10 tranny with SCX10 F9 rear currie running 38/13 diff gears which gives me a slight overdrive in the front which is perfect for U4 and hills.

My 32p steel Robinson Racing spur and pinion combo with the Tekin Pro4HD 3000kv motor is 54t spur and 17t pinion.

The torque on 3s is perfect and the speed is just right.

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Re: Proper Rear Trailing Arm Geometry
 

Nice work. Your rig looks great.

I fitted Yeti rear trailing arms and links on mine for a while, but found with the longer wheel base the TH got way more hung up on rocks than compared to the stock length trailing arms, so put the stock arms back on. Have you found this also?

Also I couldn't detect any improvement with regards to the handling with the Yeti trailing arms fitted, although my TH is wider since adding B5M front suspension arms and 14mm hex adaptors on the rear axle. Could be a different story with a stock width rig. Have you found any change with the handling on yours?

Re: Proper Rear Trailing Arm Geometry
 

Thank you...
High speed is better but, she is still short enough to turn well plus I have slight overdrive and open diff in the front.

She doesn't hang up so far. Wait till my first race and I'll folllow up on that.

I also have a Tbone racing front sub skid so I can hit hard and slide more so than before over the rocks.

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Re: Proper Rear Trailing Arm Geometry
 

Just found some old 2 cf so I made the sandwich plates for the trailing arm mounts. These will allow me to mout the upper links a bit higher... took the measurements off the Yeti.

Sealed the cf with ca... tomorrow bolt up and see if they work.

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Re: Proper Rear Trailing Arm Geometry
 

So the CF link mount plates are made and mounted. Hopefully I can test them a little tomorrow.

Static testing looks promising...https://uploads.tapatalk-cdn.com/201...4ad02217c9.jpghttps://uploads.tapatalk-cdn.com/201...f39d8e08c0.jpghttps://uploads.tapatalk-cdn.com/201...829277baef.jpghttps://uploads.tapatalk-cdn.com/201...a94d681037.jpg

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Re: Proper Rear Trailing Arm Geometry
 

So I have driven the rig around and really like its handling. I am not in love with the Vaterra front CV's.

I would like to find an alternative but, I do not want to go and change the arms.

Does or can anyone make a custom set?

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Re: Proper Rear Trailing Arm Geometry
 

What part about them do you not like?

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