540i Swapped Rat rod Build thread

[Jdesign]

Nice work! Solidworks?

I have so many questions.(Sorry) Is there a reason you are going with a cantilever set up? How did you calculate the the pivot arm length? Are there any shear concerns with the shock mounted on the top of the tube like that without any linear support? You obviously peaked my interest. I like what I see and I am very glad this isn't a dead thread.

[straight6pwr]

very cool!

Jdesign said:

 Is there a reason you are going with a cantilever set up?

seconded. it appears there is room for the coilover where you've placed that yellow connecting rod. are you using an undersized spring/shock and but increasing its effectiveness with the pivot arm?

what is the connecting rod coming forward from the pivot arm?

[m42b32]

straight6pwr said:

what is the connecting rod coming forward from the pivot arm?

Sway bar link maybe?

Looks great! I'm glad this project is still happening

[ThatRatRodProject]

m42b32 said:

Sway bar link maybe?

Looks great! I'm glad this project is still happening

Yes Sway Bar Link Set up will be coming off the cantilever toward the front of the frame. 

Linked Will Be the Sway Bar I'm Using. Haven't Modeled It in yet. 

https://www.summitracing.com/parts/rhc-19-0001

[ThatRatRodProject]

straight6pwr said:

very cool!

seconded. it appears there is room for the coilover where you've placed that yellow connecting rod. are you using an undersized spring/shock and but increasing its effectiveness with the pivot arm?

what is the connecting rod coming forward from the pivot arm?

There is a couple reasons why i have the coil-over mounted horizontally .

1. Keep it Clear of road Hazards like Dirt, rocks, Ect. 

2. I am using a under rated spring. So with the Cantilever allows me to achieve my desired spring rate with some sacrifice of overall suspension Travel.  Because i honestly don't know what the project will weigh in at.  I may have to re-fabricate the Cantilever Section. But This may be to stiff.

[GunMetalGrey]

Yeah this project was always intriguing, but has certainly caught more of my interest seeing things being modeled!

The shear area on that upper shock mount seems reasonable if you've got good penetration welds on both plates. 

I think I saw the knuckles in a picture on a previous page, but are those a standard purchased component?

I've always thought it would be cool to do a ground up build like this, so I really look forward to the continuation of this!

[ThatRatRodProject]

Jdesign said:

Nice work! Solidworks?

I have so many questions.(Sorry) Is there a reason you are going with a cantilever set up? How did you calculate the the pivot arm length? Are there any shear concerns with the shock mounted on the top of the tube like that without any linear support? You obviously peaked my interest. I like what I see and I am very glad this isn't a dead thread. 

Yes the Cad software i use is Solid-works. 

There is a couple reasons why I'm using a cantilever.

1. I have the coil-over mounted horizontally To Keep it Clear of road Hazards like Dirt, rocks, Ect. 

2. I am using a under rated spring. So with the Cantilever allows me to achieve my desired spring rate with some sacrifice of overall suspension Travel.  Because i honestly don't know what the project will weigh in at.  I may have to re-fabricate the Cantilever Section. But This may be to stiff. 

Attached is a image of a section View of the Cantilever. 

The stack up is From the top Down. 

Stripper Bolt (Shear Strength of  82,000 Psi (Roughly 28,000 Pounds or shear force))

Harden Washer 

Thrust Bearing 

Harden Washer 

Normal Ball Bearing 

Mounting piece (Gets Welded into the Cantilever) 

Normal Ball Bearing 

Harden Washer 

Thrust Bearing 

Harden Washer 

Mounting Blacking (will get mounted to the end of the tubing, (Tubing will likely be gusseted in the future)

• Quote

• Edit

[ThatRatRodProject]

GunMetalGrey said:

Yeah this project was always intriguing, but has certainly caught more of my interest seeing things being modeled!

The shear area on that upper shock mount seems reasonable if you've got good penetration welds on both plates. 

I think I saw the knuckles in a picture on a previous page, but are those a standard purchased component?

I've always thought it would be cool to do a ground up build like this, so I really look forward to the continuation of this!

The Knuckle is a ford Pinto Spindle. Primarily Used in circle track applications.

[ThatRatRodProject]

Quick update. with some actual fab work being done.

The past couple weeks I have been putting in some hours gettin some of the front frame done. I’m gonna attach some photos if you have any questions let me know. I’ll try to explain. 

68146F60-B7C9-405D-9388-5EEEE2580392.MP4

3313FB85-223C-4B49-A9BD-F9EC8D2293C1.MOV 65AD28E0-186E-4B34-8577-045E1CC9E60F.MP4 9070B11F-FE72-4710-8BD4-5062AADA8845.MP4 BC8E10B8-81C0-4EF0-8CC0-98251DCCA8DB.MP4

[ThatRatRodProject]

87C94C13-2CBA-459A-B93C-C9D60E18578E.MOV

Attachments:

• 87C94C13-2CBA-459A-B93C-C9D60E18578E.MOV

[RobZR]

ThatRatRodProject said:

I would not recommend using a stripper bolt in this manner. They are not intended to handle lateral forces and have a inherent stress riser at the base of the thread that is prone to failure.

Ideally you would support both sides of the pivot point from the subframe.  if you must support it from one side a spool and bolt design will bend before failure, since it keeps the bolt in tension.

[ThatRatRodProject]

RobZR said:

I would not recommend using a stripper bolt in this manner. They are not intended to handle lateral forces and have a inherent stress riser at the base of the thread that is prone to failure.

Ideally you would support both sides of the pivot point from the subframe.  if you must support it from one side a spool and bolt design will bend before failure, since it keeps the bolt in tension.

I 100% agree with you. If you are using a Harden alloy shoulder bolt. But with that being said I will be mostly turning up a custom shoulder bolt . But any side load should be transferred to linear load with the thrust bearings. Not 100% transferred but lessened a great deal. I’m not saying you wrong in anyway and I will take any input I can.

[Jdesign]

CAD to Metal overnight. I like your fast pace.

What did you use to cut the parts? Waterjet?

[ThatRatRodProject]

Jdesign said:

CAD to Metal overnight. I like your fast pace.

What did you use to cut the parts? Waterjet?

I work In a Tool Shop so i May have utilized Our CNC Laser.

I did have some of this work done Prior to posting the cad up date. 

Its been after hours progress the past 2 weeks . I have 3 of the 4 Control Arms done. So you should see up-dates later this week.

Attachments:

• 982107D5-5A86-4410-A3D0-1E57EAA905F1.jpeg

[ThatRatRodProject]

Update. 

I gotta finish welding up the last control arm but here’s 3 of them. 

I used 3d printed jigs to replicate the tube lengths and made up a quick fixture. 

AD34B246-ADD6-4A4C-8B34-FB7E0FD25502.MP4

Attachments:

• AD34B246-ADD6-4A4C-8B34-FB7E0FD25502.MP4

[Jdesign]

Chugga chugga. I cant wait to see the whole assembly!

[ThatRatRodProject]

Jdesign said:

Chugga chugga. I cant wait to see the whole assembly!

I got a lot of welding to do on the subframes but hopefully soon. My ball joints are on back order sadly.

[ThatRatRodProject]

All 4 done and ready to go. They will be powder coated in the future but first I gotta get some mock-up done. 

[ThatRatRodProject]

RobZR said:

With some help from RobZR. I believe we have reached a much safer option from using a shoulder bolt. I made up this spindle design last night. This will have a castle nut and cotter pin in its end form. I did tighten it all down and I’m very pleased with how it turned out. zero play. 

[B C]

Great work man! You may also consider using oil impregnated solid thrust washers instead of roller bearing thrust washers if the loads are low enough and you want to improve environmental protection.

The castle nut is a great idea