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SteyrTMP's Seven GTR
http://www.locostusa.com/forums/viewtopic.php?f=35&t=2641		 Page 4 of 26
Author:  SteyrTMP [ November 7, 2007, 3:58 am ]
Post subject: 
KB, I initially wanted an inch more backspacing to match the Miata wheel offset, but that was as far as they went with those wheels. Personally, I'm not sure if I am going to buy my next set of wheels from Diamond... the front two seem to be off. Not too happy about that. I'll see how it goes when it's actually running.

About the roll bars, I was talking to Jack about the same thing last night. The entire back end of the frame on the IRS cars is mere decoration. The live axle build has tubing going from the bulkhead all the way to the curves in the rear, whereas the IRS cars have to delete that and figure out another way. If you look in Champion's book, some of the Locosts there don't even have rear support bars. I put mine on simply for appearance, and perhaps peace of mind for some track supervisors. Structurally, there is very little support. I was originally going to have the roll bar just for appearance, with it below my helmet line, but decided I wanted to be able to run it on track days in other tracks than the local ones.

I figure, if I'm dumb enough to roll it, I shouldn't be driving it in the first place. With a space-frame vehicle, a single roll bar really doesn't do a lot of help--even with front support, upon roll impact, the roll bar is going to crush the frame beneath it (or above it in that sense), as it is the strongest tubing in the car by far. I just don't want to marr the appearance of the car by building a full roll cage. It's not going to be a full-fledged GT car--this is the test project. If I get a chance to build a second car once this is finished, it will be a hard-top, with full roll cage.

Nate
SteyrTMP
Author:  KB58 [ November 7, 2007, 10:01 am ]
Post subject: 
Yeah I didn't mean to be insulting about your build, it was a real question of mine. If I was building one I'd have to stare that that area for a while. I agree that a cage absolutely ruins the asthetics of the Seven, IMO of course.
Author:  violentblue [ November 7, 2007, 11:00 am ]
Post subject: 
I've been pondering the rollbar/cage question since I started my build, its hard to get the right look. for an all out race, safety is number 1, but for a street / occasional autocross car, the asthetics have to win out.
Author:  SteyrTMP [ November 7, 2007, 1:30 pm ]
Post subject: 
KB... it's not an insult--as a full-fledge race car, the IRS-based Seven is a legitimate concern. Because of the way the rear is built, I really don't see any way of re-inforcing it other than building some sort of external framework. I have more reinforcement than the book car has, mainly because of the IRS; and now that the roll bar is installed, I am debating on adding a little more to reinforce that.

I think the only other way of seriously approaching the roll cage thing would to build something like Jack McCornack's build, or the Donkervoort, and build reinforcement in the pontoons, and perhaps have a hard top.

Nate
SteyrTMP
Author:  SteyrTMP [ November 30, 2007, 1:08 am ]
Post subject:  At last!
Finally! After weeks of debating, dawdling, and putzing around, I finally have the brake and clutch pedal setup finished. Not complete, but the basic idea is done. I have to fine-tune some things, and find what fasteners I am going to use, but the main idea is completed.

Much time was spent trying to figure out how to mate a Wilwood dual-master cylinder setup to Jack McCornack's pedal. I bought the Wilwood balance bar and remote bias setup, and ran into a major problem... how do I get all this on a pedal meant for a single-pushrod setup, i.e. Miata stock brake configuration? The clutch was no big deal, my only problem was that the stock pedal bracket had a metric thread, whereas the Wilwood clutch master cylinder has a 5/16 NFT pitch. So, I grabbed the grinder, ground off the original nut, and welded on one of my own. It was challenging trying to figure out how to make sure I'd be able to drive the pushrod all the way without hitting the firewall, but it worked out. I think I'm using more towards a 5.5:1 ratio, rather than a 6:1 that many use.

Fot the brakes, I had to shorten the pushrods, cutting about 1/2"-3/4" thread, and I welded tabs onto the main housing of the balance bar setup. That should be enough pedal play--it comes to about 1/2" from the firewall when floored. It'll be a hell of a lot harder once actually filled and bled. I then bolted (temporary, all bolts will be replaced with clevis pins and cotter keys) it to the pedal, and promptly ran into a problem: Between the push rods, the balance bar, and the mounting point on the pedal, there were just too many pivot points. Instead of being a half-trailer, like a semi-truck, I was ending up with a full trailer, like a hay wagon--no matter how I do it, I'm not going to be able to back up. Every time I'd push the pedal, everything would buckle.

I thought about it for a while, and came to my dad for some advise. He scratched his head for a minute, and then came up with the plan I'm using now. I tacked a rod to the balance bar, which travels through the firewall, and between the master cylinders, and then connects to a pivot point on the other end. That keeps the balance bar steady, while allowing movement, and it keeps the entire setup from jackkniving every time I hit the pedal.

Here's some pictures. I'll try to get some measurements in case anyone else wants to try the same thing.

Nate
SteyrTMP
Author:  SteyrTMP [ November 30, 2007, 1:09 am ]
Post subject:  More pictures
Here's a few more. I have to go get a picture from the side.
Author:  SteyrTMP [ November 30, 2007, 2:32 am ]
Post subject: 
Here's a few of the side.
Author:  JonW [ November 30, 2007, 9:18 pm ]
Post subject: 
Nate,

Nice solution you conjured up. I was wondering how you would do it.

You might consider locating the forward end of the strut laterally with a slotted plate to guide it. The balance adjuster sleeve will load the horizontal strut eccentrically and will induce a lateral component force trying to tilt the idler link. Also, put a block between the adjuster sleeve and the fire wall and give it a load test with a 100-lb pedal force (for some peace of mind.)

(Maybe Jack McC will pattern a new pedal with optional integral balance tube that would only have to be bored through after casting.)

Jon
Author:  JackMcCornack [ December 2, 2007, 3:12 am ]
Post subject: 
Pretty clever, Nate! In line with what Jon suggested, after you put fluid in the system, put both feet on your brake pedal and push as hard as you can on it, which for a guy of average size and strength is over 500 pounds (if a 190# guy can pick up a 60# battery and carry it out to his car, he's pushing 250# with one leg every time he takes a step). If there's a weakness in your brake system, you want to find out in the comfort of your garage. And then you might want to adjust your balance bar all the way to one side, do the pedal push again, move the balance bar all the way to the other side and do it again. You have a nice long moment arm on that rod you welded to the balance bar housing, but Jon has a good point about lateral support. Maybe a plate with a hole and a fairlead for the rod to go through; that would take care of vertical (pitch) positioning as well as lateral positioning, so you could eliminate the short bar and its two pivots, and as a wise old engineer pointed ot quite some time ago, Any component not present has infinite reliability.
JonW wrote:
(Maybe Jack McC will pattern a new pedal with optional integral balance tube that would only have to be bored through after casting.)
I'd probably make it big enough that the steel outer tube could be slid into the bored casting (and epoxied in place) so the bearing race didn't rub against the aluminum. But I'd have to sell four pedals at fifty bucks each just to pay for the tooling...my horseback estimate is it would take a dozen pedals before I hit minimum wage on them, and there are some folks who would rather see me spend my recreational development time on other projects...I'll sure consider it, but unless there's interest from builders who want adjustable bias on dual master cylinders and who haven't got their brake pedal yet, I'm more likely to do one for myself the way Nathan did his.
Author:  SteyrTMP [ December 2, 2007, 3:27 am ]
Post subject: 
Thanks, Jack... and I think what Jon's saying is to consider having the balance bar-adapted pedal to replace the original pedal, just bypass boring out the hole unless otherwise asked. How much more would the extra bit of cast aluminum cost, other than the mould itself?

As for the plate, I'm still having a hard time picturing. Could someone do a simple drawing on paint or something to give me an idea where this plate would go?
Author:  locostv8 [ December 2, 2007, 4:41 am ]
Post subject: 
SteyrTMP wrote:
KB... it's not an insult--as a full-fledge race car, the IRS-based Seven is a legitimate concern. Because of the way the rear is built, I really don't see any way of re-inforcing it other than building some sort of external framework. I have more reinforcement than the book car has, mainly because of the IRS; and now that the roll bar is installed, I am debating on adding a little more to reinforce that.

I think the only other way of seriously approaching the roll cage thing would to build something like Jack McCornack's build, or the Donkervoort, and build reinforcement in the pontoons, and perhaps have a hard top.

Nate
SteyrTMP

Backing up a bit. I have been pondering this problem a bit and think the solution is to extend the bars under the diff back to the rear then run tubes from that junction to where the back tubes mount this should provide enough strength.
Author:  SteyrTMP [ December 2, 2007, 7:15 am ]
Post subject: 
Similar to my setup. I have removable tubes under the differential, but I still think it could use something more. Who knows. I have an aluminum plate bolted to those as well, for aerodynamics, if there is such a thing on these cars.
Author:  JackMcCornack [ December 2, 2007, 1:22 pm ]
Post subject: 
SteyrTMP wrote:
Thanks, Jack... and I think what Jon's saying is to consider having the balance bar-adapted pedal to replace the original pedal, just bypass boring out the hole unless otherwise asked. How much more would the extra bit of cast aluminum cost, other than the mould itself?
I'd guess (from horseback again) it'd be between three and five bucks if it was solid. And might as well bore out the hole, since it wouldn't work for a single master cylinder pushrod any more.

"Mould", eh? You've been reading your Mini owners manual again, haven't you?

SteyrTMP wrote:
As for the plate, I'm still having a hard time picturing. Could someone do a simple drawing on paint or something to give me an idea where this plate would go?

take the ace of diamonds out of a card deck, drill a hole through the diamond, put a fairlead in the hole (a plastic bushing that will stay in place in the hole, and have an ID slightly bigger than the rod so the rod can slide in and out), weld the card (use a mild steel playing card) to the floor where the short rod bottom pivot is on the current setup, with the card parallel to the firewall. Run the rod you've welded to the balance bar tube through the fairlead when you install the pedal, and Bob's your uncle (see glossary of Mini manual for what "Bob's your uncle" means).
Author:  SteyrTMP [ December 7, 2007, 12:41 am ]
Post subject: 
I considered using the fairing idea, but I am afraid the rod would slop around too much. It's main purpose is to keep the balance bar BELOW the actual mounting point. Note the picture of it on it's side.
Author:  SteyrTMP [ December 7, 2007, 1:16 am ]
Post subject: 
Well, I've been working (a little) on the car as of late... I bypassed some pictures--I forgot to take a picture of my clutch pedal assembly tester; I've added to this batch of pics.

I finally got all the brake caliper/bracket sets together, although I am slightly concerned that the front right caliper piston might be seized, but once I put the fluid and stomp on it a few times, we'll see.

The front calipers, rotors, pads, and lines are now installed, along with the brackets.

My flex line brackets were a concern for a little while, as I have no way of efficiently folding steel. The bracket I used for the brake setup was made by hammering some steel around some 1"x1/2" bar stock, and it's just not very affective for multiple, equal parts. I sat on the thought for a while, and bing! I remembered I have some 1 3/4" tubing left from the bracket for the front upper coilover mounting bracket. It's thin, maybe 18-20 gauge, and there was enough still unmolested on my "clutch pedal assembly test piece". So, I took the grinder to it, cutting diagonally until the wheel could go no more, and then cutting it from the side, making two L-shaped pieces. I repeated again, clamped the four resulting pieces together, and attacked them with the grinder.

Note to others making flex line brackets: You need larger drill bits than 1/2, but smaller than 7/8. Believe me.

WARNING: Rant starting, if desired, scroll down until noted.

Note to ALL Locost builders: Dremel tools suck. Yes, yes, I know. Blasphemy. But in this case, it does. I love my Dremel tool. No man should be without one. It's the hillbilly's machine shop. But when it comes to grinding steel with carbide bits, it REALLY sucks. I know from experience, not just from this experience, but I had to grind all the holes for the brake master cylinders and the pedal setup, enlargening to fit.

Why do they suck, you say? Well, you see, your average angle grinder grinds metal into the metal equivelent of sand, which does what sand does: get in your eyes, nose, mouth, ears, hair, clothes, car, underwear, etc. The Dremel tool (with carbide grinding bits) doesn't do that. I could deal with metal dust. But no. The Dremel tool makes nice little fine metal shavings, which make EXCELLENT slivers. MANY of them. I first realized this when grinding for the brake setup; I went to get up and "Blast. I've been stung"1 My entire hand and wrist was covered with fine steel shavings, and when I went to brush them off, I found that most of them weren't just chilling, they were nicely imbedded into my skin. After about half an hour of plucking, duct-taping, and complaining, I returned, this time wearing some garden gloves. Not quite as bulky as welding gauntlets or grinding gloves, but enough to stop the metal splinters. Riiiight. More slivers, but at least nowhere near as many this time.

Fast forward to now. This time, I gave in and grabbed the welding gauntlets, because I found that I'd have to grind the 1/2 holes on the flex line plates a bit more with the Dremel tool. You know it. STILL splinters. I think these ones managed to somehow fall down inside the gauntlets and imbed themselves.

Moral of the story: Avoid using Dremel tungsten carbide grinding bits without a spacesuit.

Rant over.

Where was I... oh, yeah. One I ground the bracket holes out a bit, the flex lines fit, and I decided to weld them on the inside of the suspension bracket upright tubing (see picture). Once welded, I installed the flex lines, using some e-clips supplied by my favorite maintainence guy at work. (thanks, Jerry!)

Which leads up to now... the kerosene heater should be warmed up, and the garage should have gone from 13 degrees up to maybe 35 degrees, and I shall go out to install the rear brakes and contemplate on hard lines.

1 "Farmer Giles of Ham", J.R.R. Tolkien
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