Driving Impressions: Lower Stress Bar

[Bobiam]

Originally Posted by HB.

Now that I have the front and middle upper bar installed, I will be looking into adding this mod in the next couple weeks. I'm still curious as to how the 2 shorter bars will help chassis flex? Can someone explain how they make an improvement, I'm always up to learning something new :dance:

I have doubts that the 2 extra bars mean much. If you look at the rear of that alum plate where it is bolted in, that's a fairly light duty drop section of framing. It can't possibly be designed to do much in the way of providing controls of stresses regardless of what framing you attach to it. That triangular shape of the plate is likely to prevent a twisting motion but I doubt it has much work to do. I'll call 'em "Can't Hurt Bars"!!! Just one guy's opinion.

[Kirk]

Originally Posted by Bobiam

I have doubts that the 2 extra bars mean much. If you look at the rear of that alum plate where it is bolted in, that's a fairly light duty drop section of framing. It can't possibly be designed to do much in the way of providing controls of stresses regardless of what framing you attach to it. That triangular shape of the plate is likely to prevent a twisting motion but I doubt it has much work to do. I'll call 'em "Can't Hurt Bars"!!! Just one guy's opinion.

Yeah, the lower side bars certainly can't hurt. They're something simple to install (easier to install than the main bar) that can further reinforce the stress plate.

As for the drop section of framing in the very back, it was loose and almost falling off on my car when I bought it used. I assume the mounting bolts just vibrated loose. When I tightened it up (this is before I installed stress bars) I immediately noticed a difference in cornering in the car. So I do think it does something in tying the back of the stress plate down solid, and like you said, probably preventing some twist. I think that adding the side bars and triangulating the whole thing certainly would help with this function.

[Kirk]

Well I FINALLY found a place that can manufacture the different components that I want to make a really decent lower stress bar system. I just ordered one set of parts. I should then have an update and some photos sometime next week with the new parts.

What I’m putting together is a main bar that’s 3/4" steel tube. I can source stainless steel (at 3X the cost though) for the main tube, but for now I’m going with yellow zinc plated steel. Attached at each end will be some heavy duty steel rod ends. These are rod ends that are beefier than the standard 3/8” items. They’ve got a larger threaded shank so they can be used with the large steel rod. These aren’t racing rod ends since they don’t really need to move much. Instead I’ve focused on getting nice strong and well constructed rod ends for the main bar. This should be a pretty heavy duty setup that will still allow adjustability for ease of installation.

The secondary side bars are going to look just like what I posted photos of recently. The exception is that I’ve figured I can go with one size larger rod end. That also allows me to go to a larger diameter rod. In addition I’ve switched to a different brand of aluminum rod ends that are more robust with a larger shank, like the steel rod ends used in the main bar. They’re silver though, not the pretty red I showed before. The static tensile strength of these rod ends is almost double that of the ones I’ve got on my car now.

More to come next week… photos and install notes.

Kirk

[blue2000s]

Originally Posted by Kirk

Well I FINALLY found a place that can manufacture the different components that I want to make a really decent lower stress bar system. I just ordered one set of parts. I should then have an update and some photos sometime next week with the new parts.

What I’m putting together is a main bar that’s 3/4" steel tube. I can source stainless steel (at 3X the cost though) for the main tube, but for now I’m going with yellow zinc plated steel. Attached at each end will be some heavy duty steel rod ends. These are rod ends that are beefier than the standard 3/8” items. They’ve got a larger threaded shank so they can be used with the large steel rod. These aren’t racing rod ends since they don’t really need to move much. Instead I’ve focused on getting nice strong and well constructed rod ends for the main bar. This should be a pretty heavy duty setup that will still allow adjustability for ease of installation.

The secondary side bars are going to look just like what I posted photos of recently. The exception is that I’ve figured I can go with one size larger rod end. That also allows me to go to a larger diameter rod. In addition I’ve switched to a different brand of aluminum rod ends that are more robust with a larger shank, like the steel rod ends used in the main bar. They’re silver though, not the pretty red I showed before. The static tensile strength of these rod ends is almost double that of the ones I’ve got on my car now.

More to come next week… photos and install notes.

Kirk

Kirk-

I agree with your first assessment of the bars. If you've still got the original plate in place, it will absorb most of the tension in the suspension movement. The bars themselves will be mostly in compression (as the ball ends don't resist moments) so the aluminum bars are more than enough in your application.

[Kirk]

I noticed over at PPBB that Pedro is now selling a fixed, solid bar for $70 plus shipping, which is what MartinJ is referring to. The original $130 Mantis bar was adjustable though to allow easy fitment on any car. The Pedro bars do vary by 3 mm depending on whether they're for a 986 or 987, but otherwise are just a solid aluminum bar with holes drilled in the ends.

I think it’s great that Pedro is willing to give a lower cost option to those people who don’t have the skills or time to fabricate their own bars. But it’s precisely those people who need an adjustable bar that’s easier to install and will fit any model. Plus I personally think that $70 for something that’s less than $10 in materials is a bit of a stretch.

Given this situation I would be willing to consider setting up a group buy for the adjustable lower stress bar I’m working on now. The main bar, as I described previously, is 3/4" steel tube, zinc plated yellow, with very heavy duty rod ends. It’s adjustable to fit a 986 or 987 (probably Cayman too) and more than strong enough for the application.

I’ve ordered one of these bars for my own car (third iteration) and was just on the phone with the company yesterday. There is some delay because the main bar is custom made to the right length for me and the rod ends are a special order item (larger shank than normal), but I should have the parts and then photos up before Christmas.

If I put in an order to have 20 bars made I can get the price down to $65 plus $10 fixed shipping cost (continental U.S. only) for the main lower stress bar. I’m willing to do this if I can get at least 10 people interested, assuming I can get rid of the other 10 bars on eBay or the likes. Let me know by PM or e-mail at kbristol@lycos.com if interested. If I get enough responses I’ll follow up in January with a formal group buy in the classifieds section of this website.

I’d also be willing to put together something on the aluminum side bars. Again, same specs as I recently posted – a larger diameter bar with heavier duty aluminum rod ends (not the red ones in my photos) and fully adjustable. These are nice, racing rod ends though and thus are a bit pricey. Plus you’ve got two bars and four rod ends to do the side bars. You’d be looking at $95 for both, shipping included with the main bar.

Kirk

[ppbon]

Originally Posted by Kirk

I noticed over at PPBB that Pedro is now selling a fixed, solid bar for $70 plus shipping, which is what MartinJ is referring to. The original $130 Mantis bar was adjustable though to allow easy fitment on any car. The Pedro bars do vary by 3 mm depending on whether they're for a 986 or 987, but otherwise are just a solid aluminum bar with holes drilled in the ends.

I think it’s great that Pedro is willing to give a lower cost option to those people who don’t have the skills or time to fabricate their own bars. But it’s precisely those people who need an adjustable bar that’s easier to install and will fit any model. Plus I personally think that $70 for something that’s less than $10 in materials is a bit of a stretch.

Given this situation I would be willing to consider setting up a group buy for the adjustable lower stress bar I’m working on now. The main bar, as I described previously, is 3/4" steel tube, zinc plated yellow, with very heavy duty rod ends. It’s adjustable to fit a 986 or 987 (probably Cayman too) and more than strong enough for the application.

I’ve ordered one of these bars for my own car (third iteration) and was just on the phone with the company yesterday. There is some delay because the main bar is custom made to the right length for me and the rod ends are a special order item (larger shank than normal), but I should have the parts and then photos up before Christmas.

If I put in an order to have 20 bars made I can get the price down to $65 plus $10 fixed shipping cost (continental U.S. only) for the main lower stress bar. I’m willing to do this if I can get at least 10 people interested, assuming I can get rid of the other 10 bars on eBay or the likes. Let me know by PM or e-mail at kbristol@lycos.com if interested. If I get enough responses I’ll follow up in January with a formal group buy in the classifieds section of this website.

I’d also be willing to put together something on the aluminum side bars. Again, same specs as I recently posted – a larger diameter bar with heavier duty aluminum rod ends (not the red ones in my photos) and fully adjustable. These are nice, racing rod ends though and thus are a bit pricey. Plus you’ve got two bars and four rod ends to do the side bars. You’d be looking at $95 for both, shipping included with the main bar.

Kirk

Kirk:
First of all my Technobrace is not just a bar with holes in the end.
The Brace is carefully machined to fit perfectly on the lower suspension supports.
They are also machined so that the hex bolt's head is secured and therefore tightened without the need of a wrench for the top portion.
It may be $10 in materials (solid 22.2 mm aluminum rod plus two automotive-grade hex bolts) but there's a lot of labor involved as each Brace is handcrafted to assure perfect dimensions and perfect fit.
It is this precisely that makes it much simpler to install than an adjustable brace. There are only two bolts to tighten and that's it.
There's nothing wrong with an adjustable brace, I just decided to simplify my version and make it more affordable to manufacture.
You also talk about a group buy being more affordable. If the group purchases 20 TechnoBraces from me I'll bill them at $59 each.
Happy Boxstering,
Pedro

[Kirk]

Pedro,

You are correct. Your Technobrace is not just a bar with two holes on the end. There are also two flats.

I don't question that it will work. Until recently I had a 1" diameter solid aluminum bar with two holes on the ends and flats on my car since August. I measured perfectly. I drilled perfectly. It didn't fit the first time. I measured again, I drilled again, still had trouble fitting. After quite a bit of screwing around I eventually got it to fit. That's just the way this kind of thing goes.

The problem is that no matter how perfectly you measure it and drill it for your car there is no assurance that it will be perfect for my car. I can't imagine there's a huge amount of difference between cars here, but it wouldn't take much to make fit a real issue. Just 3 mm difference between the 986 and 987 means you offer two different size bars. Is that really a difference in the structure between those models or a difference between the individual cars you measured? How many cars did you measure to get your perfect numbers? What about the S? What about the Cayman? I'm not trying to be nasty, just making a point.

That's why I moved to an adjustable bar with adjustable heim joints. It'll fit any car and is more of a universal solution. I also feel a bit better about having something that's made for racing and rated for 7,000+ lbs tensile (aluminum heavy duty heim joints) and 9,000+ lbs tensile (steel heavy duty heim joints).

Ultimately people will chose what "fits" best for them. And either way at least folks now have MUCH lower cost options to the Mantis bar.

[roadracer311]

Anyone have photos of Pedro's solid brace? (installed?)

Pedro, do you have a photo you could post?

[ppbon]

I don't want to get into a big discussion about this.
It's not like I make a living out of it.
I'd have everyone make their own, but for those that don't, I offer my TechnoBrace.
Every Boxster that I've tested has used one of my two Braces (3 mm difference) and they fit perfectly without any re-drilling or pulling or pushing.
The bolts drop right through.
There are many reasons why a home-made Brace will have problems fitting perfectly.
Because the securing bolts have to go through the Brace, the Suspension Support, the Skid Plate and the Structural Brace everything has to align especially the drilled hole. The thicker the bar the harder it is to make it perfectly vertical unless it's done with special equipment such as a drill press and/or a lathe. It the hole is off vertical in any plane by 1/2 a degree or more you will have to fight with it to fit.
I'm a mechanical engineer by training, so I know what I'm doing.
Think about this: The skid plate is part of the support structure. Do you think that Porsche manufactures a different skid plate for every car or is it an adjustable skid plate? Come on, when mechanical things are manufactured properly with the proper equipment they simply fit.
The main reason why I decided to manufacture a dedicated Brace and not an adjustable Brace is for strength. A solid Bar is stronger than one with an adjustable end. The heim joint itself may be rated at 9,000 lbs, but because it is screwed into the brace, at the point of union with the brace it will loose strength as a whole. Go test it if you don't believe me (I'm sure someone can do some destructive tests for you to measure the exact strength of the brace).
A chain is only as strong as it's weakest link
Now, all that being said, most of the Braces out there whether home made or professionally made are way stronger than they need to be because the Brace works against compression/deflection, and anything over 3/4" in diameter will have enough cross section to stand up to that force.

Now, some people wanted to see pictures of the Technobrace:

This is one of the ends where you can see the machining.
It has a flat part which goes over the suspension brace and a recess for the bolt's hex head so you don't need to told the bolt with a wrench (where there's very little room - making it simple for the installer).


This is the end installed on the suspension brace:


And here's a look a a TechnoBrace installed on a Boxster S. You can see the Brace right next to the anti-sway bar through the skid plate. It's the shinny one - oh yeah I also polish each TechnoBrace it after I manufacture it


Happy Boxstering,
Pedro