Baller on a Budget BBK (BBBBK)

Suspension and other discussion

Re: Baller on a Budget BBK (BBBBK)

Postby bajallama » Mon Mar 10, 2014 2:54 am

MWP wrote:
bajallama wrote:
MWP wrote:I hope those adapter bolt things have been hardened!
If its just turned mild steel, i would be very worried.

Is there a reason they should be hardened? It's in pure shear from my understanding.


Its not in clamped shear (how calipers are normally mounted) as your two turned steel 90deb bolt things are taking *all* the load in a small area.

The more i think about it, the more incredibly unsafe i think they are!
Even if they were hardened, they will still fail... i have little doubt about that.

Make proper dog-bone adapters.
Easy to do and they will be safe.


Dog-bone's were my original plan but packaging will not allow them. The bolt spacing is exactly the same between the Lexus and Celica caliper.

So you're saying under a braking load the calipers will shear through two 14mm dia. areas of steel?

What is clamped shear? Do you mean the preload?

To stop an All-Trac at 1.25 G's, 1500 ft-lbs of Brake Torque is needed per front wheel.

(Cool little calculator = http://www.jakelatham.com/radical/info/ ... tors.shtml )

I had calculated the Brake Torque from the Caliper Clamp force for these calipers and rotors and it came out to only ~850 ft-lbs (all dependent on pedal pressure), but for sake of argument lets go with the larger number.

To react that moment the point of shear is of question. I haven't gone out and measured it, but say its at about 3/4 to the rotor edge from the center.

Rotor is about 1' in diamter, 6" in radi. Caliper adapters are 4" from center.

3750 lbs force reacted at brackets.

Cold Rolled has a yield strength of 36,000 psi

Shear Strength = 36k * .6 = 21,600 psi

3750/2 = 1875 lbs force per adapter bolt thing

Shear Stress = F / A = 1875/.24 = 7812 psi

Factor of Safety = 21,600/7812 = 2.76

Let me know if any of my calculations are wrong and if I made some improper assumptions.
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Re: Baller on a Budget BBK (BBBBK)

Postby athousandleaves » Mon Mar 10, 2014 7:35 am

Ok, ok, we get it.

Just relax, nobody is trying to attack what you've done. I'm sure everyone here is happy to have another educated and motivated alltrac owner in the community.

Nobody has said what you've made is categorically dangerous but we're all asking good questions that will hopefully help you strengthen your design and possibly produce something that some members will be interested in.

Speaking to your earlier reply, if the stock braking system was failing as you had described when these cars were new there likely would have been a serious recall many years ago and the cars would have earned a reputation for this. By saying that you drive the car the way its supposed to be driven do you mean the way it was engineered for commuting or how you think its a rallye car? These cars were designed for city and highway driving conditions and not much more than that, especially if the power output has been increased. Plus you're trying to compare the braking performance of a starlet that was probably well below 1000kg with some form of upgraded brakes versus a car that is into the 1400kg range? How is that comparison at all valid?

While the calipers that you've chosen ARE SAFE the way you've gone about getting them onto the car could do with some more thought. If the way you were doing it was completely sound then why wouldn't more manufacturers like AP Racing be doing it the same way?

As for the ball joint, the 165 uses a different front A arm so they're not compatible with the 185.

Also, personally I find it wise to avoid prefacing any thread with your profession if you're trying to gain trust. Using your background to leverage confidence on the internet can be difficult as usually word of mouth will carry more weight than just saying you've finished a program at school.

I'd be curious to know what the safety factor is on the stock caliper for comparison. :smokes:
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Re: Baller on a Budget BBK (BBBBK)

Postby bajallama » Mon Mar 10, 2014 1:08 pm

athousandleaves wrote:Ok, ok, we get it.

Just relax, nobody is trying to attack what you've done. I'm sure everyone here is happy to have another educated and motivated alltrac owner in the community.

Nobody has said what you've made is categorically dangerous but we're all asking good questions that will hopefully help you strengthen your design and possibly produce something that some members will be interested in.


Haha, I guess you took my tone as defensive, it's not at all. (Except for the case where it was claimed as not a real brake kit, which I see that as somewhat unnecessary and far from constructive) When I mean the car will be used as it's supposed to, I don't mean commuting everyday (Although I will be doing that). Is your view of the car a simple commuter? I like the car for the nostalgia and the value. From my understanding, it's the same chassis and drive train that was used in WRC. But when a Kia Soul has better braking performance, doesn't that sound an alarm? Again I'm not trying to attack, but just state the obvious. My comparison with the Starlet is that it's not a car meant to be driven, it's an economy car. But I drove it the way it wasn't designed with a brake upgrade that was minimal in performance (went from solid to vented 25 year old rotors and still used $25 brake pads). This car is a performance car, I'm sure that's why a lot of people own them today. I am really surprised why not many other people have not had issues. I mean every time I take the car out at night, all 4 rotors are glowing red! None of my friends cars nor none of my previous cars have done that.

Yes I agree, I don't want to take shortcuts but I am always open to suggestions! I have no other options for a design to retrofit, though. But if you have ideas, throw them my way. I already had to lose the rear UCF calipers because packaging would not allow. Dog-bone style adapters are typical because that's what applies to their package, but the bolt spacing is the same between the ST and the UCF. Therefore I make a simple adapter as shown, or I make a very odd aluminum dog bone that moves the caliper in a different clocked position. I plan on seeing what the FOS is on the stock caliper, and being cast iron, I don't see it being much better.

I don't care about anyone's trust to be honest. I'm here to offer my knowledge and skill to the community, trust me or not, the results will show (If you know what FSAE is then you know what I have seen and done in order to offer everyone). I'm not hiding in my garage doing mystery things to my car, I'm sharing my design with you guys so you to can have a car that will give Porsche's and Lambo's a run for their money. Since I live in LA, I have the chance to make guys cry when they see an 80's Toyota keep up with their R8's and brand new M3's. It's the best feeling in the world to be truthful.
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Re: Baller on a Budget BBK (BBBBK)

Postby bajallama » Mon Mar 10, 2014 4:27 pm

Oh and I thank MWP for questioning my bracket and in no way was my response an attack on him. I honestly believe it was far from strong and thought I would retain a higher FOS. But it does bother me even at worst case having FOS of 2.7. I did the same calcs for the 10.9 bolt and it came to around 8 and I want to match that at least, so I am looking into alternatives (maybe 4140 or a complicated dog-bone).
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Re: Baller on a Budget BBK (BBBBK)

Postby MWP » Tue Mar 11, 2014 2:11 am

I got not sign of a defensive tone when reading that reply :)
Its good to see you calculating it out.

I need to draw an image....
A normal dog-bone wouldn't have the same swivel problem as its fixed in two places to the strut, eliminating the side load on the studs.
You would also bolt up the dog bone with 8.8 or 10.8 bolts which are far stronger than those studs.
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Re: Baller on a Budget BBK (BBBBK)

Postby bajallama » Tue Mar 11, 2014 3:19 am

Brake Force direction is other way! :P

Yes I understand what you mean, I had a talk with a stress engineer today at work about the design. I saw it as a non-issue as is because the brackets are so close to the calipers that the rigidity of the caliper and the hollow indexing dowels would make up for any need of a bridge or tie as the dog-bone incorporates. But again as stated, packaging of a dog bone is very tough since the bolts will intersect each other. He seemed to understand that the hollow dowels in the caliper take all the shear load and index the caliper. This makes sense as the bolt is just slopping inside the holes and really just take up what little outward component force there is (the bolts are not perfectly tangent to the center) and keep the caliper tight against the upright. So I measured the minimum thread engagement and it barely squeeks by, by like .025. So I guess an aluminum dog bone it is with steel threaded inserts probably. I may possibly put the adapter to upright bolt in double shear since I have the room, but will cost me machine time. I'm getting my 3D printer Wednesday so I hopefully can have something mocked up by the end of the week. Thanks for the advice!
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Re: Baller on a Budget BBK (BBBBK)

Postby underscore » Tue Mar 11, 2014 4:03 am

If you had the same bolt/stud setup you have now but had a connection between the cubes, wouldn't that be enough to keep them from rotating and causing a weak point? Or since the bolt spacing is the same, you might have to just offset the caliper from the normal position a bit. The adapter would look funky but it should be able to work, no?

bajallama wrote:Brake Force direction is other way! :P


He's Australian, you should know that those guys do everything upside down and backwards.
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Re: Baller on a Budget BBK (BBBBK)

Postby bajallama » Tue Mar 11, 2014 2:46 pm

Haha, probably. Yes, I can't believe I never mentioned it but there is another piece to the bracket. It indexes on those steps that are on the shafts and holds the two bolt adapters together. Yes it helps with the shear force but since there is always slop in loosely mounted components, I never saw it as nothing but a locator.
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Re: Baller on a Budget BBK (BBBBK)

Postby underscore » Tue Mar 11, 2014 3:03 pm

Could you not either incorporate it into the design to turn the three pieces into one, or just get it welded together to be one piece?
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Re: Baller on a Budget BBK (BBBBK)

Postby bajallama » Tue Mar 11, 2014 4:38 pm

Ya that's the plan with the dog bone design. The problem with welding is the strain it puts on the metal. It would need to be treated after to be normalized, etc. As MWP said a dog-bone is the easiest way and can be made from Aluminum. I just had my doubts on the ability to package it since these calipers are so large, but I think I can do it now. It's going to be a somewhat exotic design however.
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Re: Baller on a Budget BBK (BBBBK)

Postby bajallama » Tue Mar 11, 2014 7:01 pm

Here is the brake kit from TRD for the Altezza. The adapter will be very similar as shown.


http://www.trdparts.jp/english/parts_monoblock.html
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Re: Baller on a Budget BBK (BBBBK)

Postby 801Alltrac » Wed Mar 12, 2014 2:37 am

Thus looks awesome and I'm on board, can't wait to see more
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Re: Baller on a Budget BBK (BBBBK)

Postby bajallama » Wed Apr 02, 2014 4:20 am

Sorry it's been a while, I've been going buck wild with my 3D printer and finally got around to printing the new bracket design. Here's a pic of what they will look like. Everything bolts up nice so the design should be good to go.

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Re: Baller on a Budget BBK (BBBBK)

Postby MWP » Wed Apr 02, 2014 1:11 pm

Much better :D
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Re: Baller on a Budget BBK (BBBBK)

Postby ALLensTRAC » Fri Apr 04, 2014 1:49 pm

Can I ask what was the issue with the rear UCF30 calipers? If the rotor was a larger diameter could a dog bone be fabricated given the increased space for mounting? Was it the rotor offset?
The reason I ask is I am going to run MKIV turbo rear rotors which are 324mm diameter with the same width as LS rotors. The supra calipers are super expensive but the LS ones aren't. Any insight would be greatly appreciated!!!!
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