Any time you apply an accelerative or decelerative force to the rear axle it wants to wrap around. Resisting that wrap is what pushes you down the road in the end. The problem with a solid bar is that when things try to wrap there's no give, so the only place to give is on traction. The biscuit bar puts a poly bushing on the movement to give it just a little give, which means you can, in the end, put more power down.
The Busa powered dwarf car that races with us has a sprung version with a 1,200lb spring on it. His tell tail says he gets an inch of compression under acceleration. That's massive.
This unit is lighter than the sprung models.
Grabbed some shop time yesterday and quickly tweaked my back. My plan for bending tube and welding was a no-go. Instead I did some light duty sheet metal restoration. The fire wall was in pretty lousy shape so I did a lot of hammering with a dolly and re-bending before stripping old paint and throwing on a coat of white. This will all have DEI gold applied after to keep the header heat out of my foot box.
I think I'm going to throw these at the bead roller to add a little more rigidity too. Should have done that prior to paint...
I'm looking forward to some video of this thing. Keep up the good work.
How are you plugging the hole in the engine case left by the water pump?
Pulled the diff out and rolled the chassis over to finish all the bottom-side welding. Good thing it was only 86 degrees in the shop... I could have shown the metal a picture of the arc and it would have stuck together.
Building a race car is pretty much putting things together, taking them apart, putting them together, taking them apart. Eventually you're happy with the result and you can break the cycle!
After sweating for a couple hours in my lid, I decided I didn't want it to look like the three other idential Vulcan welding helmets in the shop. Time for some arts and crafts.
A little white and then GOLD
I'm letting it cure overnight and will spray clear tomorrow. Now I don't have to wonder which one is mine.
In reply to TVR Scott (Forum Supporter) :
If only I could get that chrome gold finish looking right!
Being Covid-ed out of a job has an upside - I can get to the shop early and beat the heat. New job is lined up starting July 6th so I'm running out of chances to do such things.
After much hemming, hawing, bending metal and holding it in place, throwing that metal in the scrap bin, waiting a few hours and trying that pieces again, I finally settled on a setup for the biscuit bar.
I still need to burn on the actual mount and one more piece going down to the chassis, but this is it. It also pulls duty as broken driveshaft protection for me. It has to be a fairly strong assembly given the forces involved. The Busa powered dwarf car that runs with us has a tell-tale on his sprung biscuit bar that shows an inch of movement with a 1,200lb spring. His car is about 200lbs lighter than mine too.
This bar's sole purpose was to make things more symmetrical. I'm not great at coping, so it took some time, but I'm happy with the fit up.
To cool off I did more sheet metal work. I replaced places that had been riveted with rivnuts so things can be serviced without a drill. Applied a bunch of DEI gold foil as well to help reject heat from the headers, which are right on top of this. Hopefully between the header wrap, the foil, and some insulation on the other side of the metal my feet won't get cooked.
Header routing for reference:
My welding is improving, which is good because I finished up a LOT of it today so I could roll the car over and start painting.
I'm going to paint the chassis white, but I had some very light gray implement paint from spraying the interior of the lemons car. Figured I'd used that on the surfaces most likely to touch the ground.
I'm girding my loins for tackling the wiring, which is almost all from the motorcycle. I don't want to mess with a lot of that, but I also need safety equipment and more circuits so I'll be making changes.
Nice penetration! hehe
But seriously this thing is gonna rip. Is there a target event for this thing to.make its debut? I'd definitely volunteer to see this baby in action!
In reply to golfduke :
Things are still getting canceled unfortunately. My goal is to have it running around naked before the end of July. The carbon panel interior will take some time after that. I'll see what's available for events after that. Would be great to go down to Devens. The car ran in DM before.
Another big day in the shop, this time with Sherman leading the charge. Sherm runs the Busa powered dwarf car at our hillclimbs and his experience not only with Busas but in general was much appreciated.
The gearset dropped right in and was the easiest part of the day. Making sense of the cams took a lot more time.
What you're looking at is two intake cams. Yes two. That isn't a mistake. Suzuki "undercams" their exhausts so a common trick is to run an intake cam in the exhaust position. It's so common in fact that many adustable cam gears come with markings for running an intake cam this way.
The issue we found, was that the exhaust cam was timed WAY off. It took us a while to get it all straightened out, and we reshimmed a couple tight valves while we were at it. In the end she should make some nice power and the double-intake-cam trick nets a broader torque curve as well.
Now the engine is all together and ready to be popped into the chassis. Right after I finish painting it.
nocones
UltraDork
7/1/20 10:58 a.m.
DaveEstey said:
Speaking of pedals, these masters are gross. I'm going to swap them out for some Wilwoods I had and I'll swap the clutch master with a fresh Girling.
What size are the old ones and do you still need them? Challenge cas need cast off master cylinders..
DaveEstey said:
What you're looking at is two intake cams. Yes two. That isn't a mistake. Suzuki "undercams" their exhausts so a common trick is to run an intake cam in the exhaust position. It's so common in fact that many adustable cam gears come with markings for running an intake cam this way.
That is a common mod here in South Africa on the 16V VW motors, especially the ABF(2.0 16V Efi) import motors, just by using 2 KR(1.8 16V K-Jet/CIS) intake cams. Gives you a broader torque curve.
Why is there welding on the right side cam end?
In reply to nocones :
I haven't checked. I'll get back to you on that.
In reply to StripesSA1 :
The cam gears are pressed on. Sometimes that isn't enough to keep them from rotating on the cam so you add a bit of tig to the mix.
Started painting the chassis today so I can bolt the suspension back on. This is Ford light gray. The humidity was making the paint take FOREVER to dry, so I'll have to wait a day between coats.
Here's how the stock air box mounts. Far too high to fit under the car's hood.
Here's a rough sketch of my idea. It will need to be even lower than this, but I'm treading a fine line of being low and shrouding the intake trumpets.
