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nocones GRM+ Memberand UltraDork
11/4/20 10:58 a.m.

Not a lot of progress last night..  I was distracted by things.  But I did get the knee braces welded and CAD templated the plates that will be added to more easily attach the front support tubes. 

nocones GRM+ Memberand UltraDork
11/5/20 10:11 a.m.

And in another hour, cardboard becomes metal and gets glued to the car with electrons.  

The idea here is that I can just MIG weld square tube to this plate and run it to the front Bulkhead. Which hopefully happens tonight.

AxeHealey GRM+ Memberand Dork
11/5/20 10:45 a.m.

I like when my mental breaks take me to GRM and this one is up top. 

nocones GRM+ Memberand UltraDork
11/8/20 11:12 a.m.

Got a bit done over the last two evenings.  I cut the inner sleeves to start on the suspension Inboard pivots.  

I also got all of the upper braces in on the front bulkhead.  

I'm happy with the fit of the tubes to the body.  It should be easy to bend up a few tabs to use the stock fender holes to hold the body on and bend a sheet of aluminum to go down and make the lower body/chassis side.  

I think next I'm going to work on getting the front suspension points finalized.  

Another 3.5 hrs = 77.0

Tube / Metal used is now:

Chassis: 4130 - 585.75"@ 6.50/ft = $317.28; 2x2 - 267-3/8" @ 1.67/ft = $37.21; 1x1 tube - 132" @ $0.67/ft  = $7.48;  .75x.75 tube - 41.5" @ $0.69/ft = $2.39; 4130 Plate - 0.89 sq-ft @ $11.00/sq-ft = 9.80

Suspension: 1" x 0.120 Wall - 27.2" @ $1.35/ft = $3.06;  3/4" x 0.156 Wall 4130 - 29.6" @ $0.50/ft = $1.23

Total = $384.66

rustomatic Reader
11/8/20 3:56 p.m.

This is awesome so far.  On many levels, I kind of think this is the best stage of the build process.  The planning/structuring/cutting/application of tubing is just so cool a thing for triggering and applying the imagination.

nocones GRM+ Memberand UltraDork
11/8/20 4:18 p.m.

I agree.  It's fun because you have to think ahead, and see things that aren't there yet.  It's also great because there are so many ways to do it.  It's like, "I have to support this thing here, my closest other thing is over there, how much and what type of structure do I build".  Oh and I want it to be light and use the least overall tube. 

It's great!

nocones GRM+ Memberand UltraDork
11/12/20 12:04 a.m.

And I had to cut something out that I had put in.  But it's ok I knew it was going to happen.  Today was try to generally locate the steering rack because for real we are going to start putting the front suspension pickups on and things better fit or I'm going to have to rage grind later.  So I did that.  The steering rack input pinion wants to live exactly where my node is.  This was not unexpected.  So out came the saw, I cut the 5 tubes and started to build around it.  Just to check I located the rack and intermediate shaft.  The steering column joint is going to have to be all the way back at the dash bar because the steering wheel needs to be above the dash bar vertically.  If it is and a straight column is used the clutch foot becomes isolated from the brake pedal which is no bueno for LFB.  I briefly thought about a Y shaped brake pedal (and may still do that for LOLZ) but the short column with long intermediate shaft seems like the better solution.  My foot fits beneath the intermediate shaft joint and can freely traverse the pedal box. 

DeadSkunk  (Warren)
DeadSkunk (Warren) PowerDork
11/12/20 5:39 a.m.

In reply to nocones :

Great build. Good narrative. I love the term "rage grind" !   I've had to do it more than once on my build.

nocones GRM+ Memberand UltraDork
11/13/20 9:49 a.m.

Suspension points have been located!  I welded in the plates that are going to support the captive nuts (Getting my Inner Binky on) for the rear bushings for the front suspension.  To drill them I just used the inner bushings as a drill bushing.  I'm using Grade 5 fine thread 3/8 bolts for the suspension pivots.   Next step is to put the jig back together, weld the captive nuts in, then locate the actual front suspension tubes.

I also cut the intermediate shaft apart for the steering and mocked it up to make sure I will have clearance.  I will leave the rest of the reinforcing of the removed node until after the front suspension is done which is required before I finalize the location of the steering rack.  


Another 1.5 hrs (+3.5 from the previous updates) = 82.5 Hrs

4130 plate used since last update: 6.75 sq-in = $1.03

Dusterbd13-michael (Forum Supporter)
Dusterbd13-michael (Forum Supporter) MegaDork
11/13/20 10:37 a.m.

Whats the reasoning behind the grade 5 fine thread hardware? Id have gone straight to grade 8 minimum,  but dont actually have a reason why except "grade 8 stronger"

nocones GRM+ Memberand UltraDork
11/13/20 11:22 a.m.

In reply to Dusterbd13-michael (Forum Supporter) :

I don't have a real reason other then at the store I went to Grade 8 bulk fasteners are only available in coarse thread (And are $2/lb more expensive).  I prefer fine thread because Carrol Smith called coarse thread "Speed nuts" and taunted their use.  

I did review the loads and think that Grade 5 is fine for this application.

Grade 5 3/8 bolts have a shear strength of ~8200lbs, and when torqued correctly a clamp proof load of 5600lbs

Grade 8 3/8 bolts have a shear strength of ~10000lbs, and when torqued correctly a clamp proof load of 7900lbs

The suspension will all be mounted in dual sheer with 2 bushings per A-arm.  Meaning to damage a bolt will take a load into the Ball Joint of 32000lbs, or 16 Tons.  The Outer ball joints have a single shear cross sectional area of ~13mm meaning they will shear at about the same load as a 1/2" bolt.  Even if these suspension joints where made of Inconel (Which they are Not) the peak load would be <23000lbs.  Which would break first.  Additionally the A-arms are going to be made out of 1" OD x .120 wall tube and those will have lengths of >10".  Buckling loads for these arms would be less then 13,000 lbs.  I am comfortable with the load capacity of Grade 5 hardware in this application.   

Would grade 8 be better?  Objectively yes but I'm not sure it's necessary as it won't be the weak link.   

Dusterbd13-michael (Forum Supporter)
Dusterbd13-michael (Forum Supporter) MegaDork
11/13/20 12:52 p.m.

Thanks! The decision tree you outlined is exactly what I was hoping to learn!

Robbie (Forum Supporter)
Robbie (Forum Supporter) GRM+ Memberand MegaDork
11/13/20 3:30 p.m.

I read something somewhere that grade 5 has better heat tolerance or springs back to original shape better or something. It was in reference to using them over grade 8 for brake calipers. 

Might have been 100% bull. 

nocones GRM+ Memberand UltraDork
11/13/20 4:06 p.m.

The adage as I've always heard it is that Grade 5 is more ductile then grade 8.  Which is true.   But like all rules of thumb isn't the whole story and isn't really correct.

For those who don't know I'll briefly explain how a material fails (skip to next paragraph and ignore if you know this already).  A material has what's known as yield strength, and ultimate strength.  Below the yield strength deformation will be elastic and the material will bend but not deform.  Meaning it will return to it's original shape when the load is removed.  Past yield the material will begin to permanently deform plastically, when the load is removed the material will not return to it's original shape.   At some point with increasing load the deformation will be so great that the material will catastrophically fail, this is called Ultimate strength.    The amount of deformation that a material will allow is considered it's ductility and is generally expressed as a % elongation.

Ok so back to bolts.  Once plastic deformation occurs (Bolt is loaded beyond yield) the Grade 5 hardware will deform a greater % before ultimate failure.  But, the Ultimate strength of a Grade 5 bolt is beneath the yield strength of a grade 8 bolt.   That means that if you are relying somehow on the Safety of deformation in the ductile range of a grade 8 bolt you already would have completely failed a grade 5 bolt of the same size.  

Now that said in a properly designed bolted joint you will torque a bolt it's proof strength which is ~85% of yield.  This is really the load you should design your bolt around.   The proof load clearly depends on the bolts diameter.  There are situations where the load you are carrying may be able to be carried by either a Grade 8 bolt of a smaller diameter or a grade 5 bolt of a larger diameter.  In this condition you may choose to use the Grade 5 to provide some amount of bend/not break ductility.  But to overall say that Grade 5 is better then Grade 8 doesn't really make sense.  

For brake calipers the other part is that there is some concern with low ductility materials in corrosive environment.  Low ductility + corrosion can cause Stress Corrosion cracking depending on the materials used.  I didn't think the steels used for Grade 8 were susceptible to that but there is talk on the internet that some companies have rules of thumbs that they follow that exclude Grade 8 or above in  corrosive environments for this reason.  So that may be part of it.  

nocones GRM+ Memberand UltraDork
11/15/20 12:38 a.m.

Got only an hour tonight so I decided to throw together one inboard bushing to give it a try to see how it works.  

The parts to make one are:

1.8" of 3/4*.188 wall 4130 bored to 3/8.  

1.65" of 1"x.120 wall DOM

2 5/8 SAE washers bored to 3/4 ID. 

1 3/8 x 2.25 GR 5 bolt and nut.

All told it's about $0.70/joint.  

Add some Metal glue and inboard bushing!  There is .010 radial and .005 axial clearance.  It's probably a bit more then ideal, but compromises must be made to the gods of low cost.   I will fill them with all the grease also.  Compared to the compliance of any kind of rubber/delrin I don't think it's unusual.  If it causes any issues long term I will replace them with rod ends. 

That said this is the exact setup I have outboard of the MG rear and there has been no issue with it in 3 years of use and about 10 hours of tracktime. 

Dusterbd13-michael (Forum Supporter)
Dusterbd13-michael (Forum Supporter) MegaDork
11/15/20 5:36 a.m.

Yeah, im pretty sure the ub machine upper control arms i ran on the s10 had more play that that. They lasted 30k on the street 

jfryjfry (Forum Supporter)
jfryjfry (Forum Supporter) Dork
11/15/20 8:35 a.m.

I'm no expert (although I have played one on tv...) but I think I would sort out that nodal interference resolution before doing suspension work. Enough is happening there that your solution might end up tweaking the frame a little (with shrinkage and whatnot) and potentially move suspension points.

I so enjoy reading the updates and seeing this thing come to life!


Fascinating bolt talk.

You obviously know your E36 M3, but I have to ask, are you doing metal on metal bushings for your A-arm pivots? In single shear?

I ask because I want to learn, not because I question your engineering. 


nocones GRM+ Memberand UltraDork
11/15/20 11:50 a.m.

It's a good question and one worth explaining why I think it's ok.  I appreciate people questioning because it makes me think it through better and would hopefully find any bad reasoning I'm using before I get to comitted to a bad idea.

The inboard pivots will be Metal/Metal in Double Shear.  The second shear plate will be added once the remaining structure is built for the suspension in front of the bulkhead. 

Metal/Metal would be similar to most "Economy" 2 piece rod ends or OEM ball joints.  There are 2 major differences that will be deficient in my design.  Typically the ball on these is a hardened / chrome alloy steel.  Mine will just be 4130 Alloy Steel (The body is typically some kind of Mild Steel).  The second is tolerances.  A Production ball joint/rod end may be .001 or .002" play.     My design will  result in .010 Radial, ~.005 Axial.  

The "Improper" inner race material will result in increased wear, however I am combating that by using much larger bearing area so contact pressure will be very low.   A 1/2" rod end would be typical for this application and those are about 1/2" wide, my bearing is 1.8" long so contact force is  360% higher.  Additionally I am going to use grease/anti size compound to prevent galling and other small clearance corrosion that may occur.  I also will be able to inspect/lubricate these joints frequently.  

The other thing I have going in my favor for use of these bushings is the incredibly low angular movement they will undergo (Relatively speaking).  The total suspension travel of this car is likely to be ~2.5" with typical travel on track being closer to 1.5".  Given that the shortest A-arm will be 12" long (Upper Front) that will be ~7* of angular travel at the bushing.  

I would be unlikely to even consider this design on a car that was going to see substantial street use.  The maintenance needs would just be too high.  

I actually seriously contemplated using Flexplates made out of 1/8" air hardening spring steel from MC-Master.   This would be similar to what F1 cars use as inboard pivots.  They would of cost about $2.50 a joint but I wasn't liking the clamp mechanisms I could come up with and thought that people would question them quite a bit at Tech inspection for other events.  

In reply to nocones :

Cool, and you already confirmed the design on the Midget. Can't beat the bearing stiffnesswink

karplus2 GRM+ Memberand Reader
11/15/20 2:01 p.m.

Moar YouTube videos!

nocones GRM+ Memberand UltraDork
11/16/20 3:05 p.m.

Working on it.  The last month has been not great mentally.  I've just not felt like editing for some reason.  I'm thinking I will get working on them in the next few days.  I believe I have sufficient footage for 2 episodes but may have to add some Voice Overs.  Which everyone enjoys my sultry voice.

karplus2 GRM+ Memberand Reader
11/17/20 8:44 a.m.

In reply to nocones :

I feel ya. I am in awe of your motivation/progress. I haven't been motivated to even get off the couch lately. 

nocones GRM+ Memberand UltraDork
11/17/20 11:28 a.m.

Last night I got tabs cut for the front suspension.  I was going to make one of those compressed electronic music montages of marking, drilling, tracing, cutting, bolting all of them together, sanding them the same..   But the camera ran out of Memory and forgot the video..  So I will try again with the rear brackets or the bellcranks.  

Front uppers are ready to weld.  Just need to tweak the fixture slightly for one of the tubes so it lays against the brackets right.  Everything is located to +/- 1/16".  I am fine with that.  

I also had someone contact me on my very old FB marketplace for the Wheels/Tires for the Brighton.  He was very excited to get them and gave me $60.  I will adjust the FMV on the spare Transmission down to $40 and that successfully Zero's out the Brighton.     

Another 1.5 hrs  = 84.0 Hrs

4130 plate used since last update: 27 sq-in = $2.06  (Previous update I had said 6.75 sq-in but I made 2 of the brackets so it was actually 13.5 sq-in, Cost was correct).

TurnerX19 SuperDork
11/17/20 6:35 p.m.

In reply to nocones :

Everything is located to +/- 1/16".  That tolerance is 4X closer than a Lola F.Ford. Tighter than almost anything built in the 20th century, and some of the current cars too.

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