12/16/06 A few days ago I was ordering some parts and realised I need an oil filter and a remote mount. No problem. Visualised the best mount configuration and ordered that, then saw 'Fram Racing Filter' and thinking it's just the ticket added that to the order as well. So yesterday everything shows up and this thing is HUGE!
Hmmm.... Well, OK, took it back home and made a SolidWorks model of it. Then, after a few tries, came up with a fairly simple bracket that will mount it where I want it. Cool.
This works. While talking to John about the oil pump belt tensioner sleeve I mentioned the bracket and it seems he'll be able to make it. Even better. So the whole plumbing scheme is coming together. Of course as always I can't do things the normal way so here is the deal. The oil cooler plumbing in the chassis is 3/4" line (about 10 feet of it round trip and there's really no room to go bigger diameter) and the radiator that serves as the oil cooler has 3/4" ports. Problem is, the scavenge pump is 3 stages, each of which can pump something like 25 gpm and generally feeding that much output into a single -12 line, especially one this long, is not recommended by anyone. Now on my side I'm thinking that the engine is fed by a SINGLE stage through a -10 line so on the average the scavenge pumps are mostly pushing air which is compressible. Even if oil were to accumulate in the sump and then flood all 3 stages at once (I suppose feasible in a scenario of braking followed by hard acceleration, all in a straight line) there would be a surge in the system. But how much of it can there be? The sump is not all that big and if it starts to fill up at all the contents are going to get whipped into foam by the crank so it won't be 'solid'. So my thinking is that the system should be able to accommodate any such surge without breaking anything. But maybe I'm being naiive? Would be curious to hear from any folks with direct experience in this (i.e. running a 3-stage scavenge into a single -12 line in a racing application and whether the result was good, bad or indifferent). Yep, yet another experiment...
12/18/06 The search for the buttonhead bolt continues. Corsemeccanica claims to have them available in titanium on their site, at a fairly reasonable $8 apiece (I just need one). Problem is they have yet to return either e-mail or phone call and there's no way to order online. Chromebolt supposedly has them in chrome at $9 apiece though this is a last resort. Maryland Metrics can supply the parts in steel, with 3-4 week lead time (they have to order from Japan), at a reasonable $0.91 each. The catch is that I'd have to buy 100 and they won't split the box. This is almost humorous. You'd think I'm trying to build a black-market nuclear reactor here. Maybe the name choice for the car was even more appropriate than I anticipated ;)
It was correctly pointed out to me that my earlier statement about helper springs was incorrect - two identical-rate springs in series result in an effective rate of half that of the individual springs (see here), not same rate. Thanks Dave. This actually means that when the helper springs compress all the way the rate abruptly doubles. Could explain some of the skittishness I had experienced when driving the Atoms. But regardless, I'm fairly comfortable with my current choice. The current wheel rates are about 0.8 X corner weights. If I swap from 30/50 to 40/60 springs the wheel rates will be identical to corner weights which is a reasonable setup for a non-aero track/race car (cars with real downforce run 5x-8x heavier wheel rates). The dp1 is also sprung at 0.8 X corner weight but it's a little wider and has much lower CG so roll is less of a concern. Interestingly, the Bikini suspension seems to move more freely without the helper springs, possibly due to reduced friction in the shocks (less bending force from spring). At this point of course this is all theoretical and I'll have to wait until I run it on the track to draw any real conclusions.
12/23/06 The buttonhead dilemma was solved by a visit to the local Yamaha dealer. Sure enough, they had the chrome bolts in stock. $18 for a pair but it was worth it just to have it over with.
The chrome bolt head is a bit hard to see in the picture but basically it JUST fits. The spring barely touches the bolt but I can rotate it on the shock body so that the coils won't contact in normal use. Ultimately though I should just redo the engine mount properly. I already have it redesigned, just need to have one made. Not the highest priority at the moment since I have a workable solution.
Next on the agenda is the shifter linkage. The cables come in at the wrong angle so I need to either do something complicated or alter the existing setup. To that end I pulled off the counterweight (it touches the frame in 1st, 3rd and 5th anyway) and now I need to figure out what to replace it with. Shouldn't be TOO difficult. Rotating the shaft goes with moving the shift lever sideways. The part of the linkage that moves when the lever goes forward and back is going to be trickier. We'll see.
Unfortunately the cables are not the ideal length and bending them increases the friction in the mechanism considerably. So I really need to solve this 3D puzzle. Have some ideas already, they should gel enough for initial CAD in a day or so. Having the gearbox CAD from Ford really helps.
Also, I spoke too soon on the DMV issue. There's a new twist (as in the policy change was made three weeks ago!) that is for the moment a show-stopper. I will eventually find a way around it, with luck, and I am pursuing one path with a couple backup plans on standby. Gotta love bureaucracies.
01/03/07 With much of the attention being directed to dp1 the progress on Bikini has been slow. Today I finally test-fit the oil tank. As with just about every single part in this project, clearances are tight but fit it does. Barely. I may modify the top part slightly to make it fit better. Good thing it comes apart, this allows me to install and remove it without dismantling the exhaust. If the fuel tank hadn't been moved forward for exhaust clearance the oil tank would not have fit at all.
The oil tank itself is actually on the smallish side for the application, only 5" in diameter which makes it about a gallon in capacity. However I should have another 2-3 quarts in the cooling circuit and the fact that the scavenged oil goes through the cooler should help de-aeration. The fact that the cooler is actually a radiator should help as well. I'll need to keep a close eye on oil pressures though, especially since back-pressure through the cooler is a potential concern as well. I will most likely set up datalogging for engine pressure, scavenge pressure and temperature so that I can see any spikes in either direction. Brammo had developed a pretty neat drysump tank solution that integrates quite well and they did a lot of testing with it. Unfortunately it is located in the area that I want to play with aerodynamically so I'd rather avoid going that route, at least for now. But it's always a possible solution to fall back on.
The other thing I did was install the thermostats and the cooling manifolds. Given the confined space to work in it's much easier said than done. But done it is, now, with minimal blood drawn (some).
Little by little it's coming together. Still no flash of inspiration on the shift linkage but I'm about due for one. First trackday is March 24 so I need to have Bikini running and break-in completed by then. Or at least that's the goal. Gives me two months for the former and three weeks for the latter - should be doable.
01/11/07 With the rare snow on the ground it's hard to think of trackdays and driving this beast... But that's exactly what I've been thinking of lately and to that end I did a bit more work. I now have a general idea of what I'm doing with the shifter linkage (after staring at it for over two hours and moving things this way and that). It's not perfect but should be quite functional and reasonably clean. I'll do it in CAD first, then figure out the best way to have it made.
A few days ago I got the oil filter bracket from Hartley so today I test-fit that. Works well.
The filter is very big and very orange. Once I use this one up I may change to something less conspicuous but the good news is that pretty much any replacement I'm likely to find is going to be smaller so it'll fit just fine. Now I need to do the plumbing. Well, after I modify and mount the drysump oil tank at least.
While staring at Bikini and thinking about driving and warmer weather, I recalled my recent (very cold) ride in John's Lotus 7 powered by a smaller (2.6L vs 2.8L) version of this motor. There was wheelspin everywhere and it was clearly too much motor for the car. I did drive it but did not want to push it even a little. My focus was instead on seeing how the engine behaves at lower speeds and it's perfectly tractable and linear with no ill temper. Pulls cleanly from 2K RPM. So the point is, with a 60% rear weight bias Bikini might utilize the motor better (once I get bigger tires on the back, at least) but it'll still be a SCARY car. One that will take me a while to work up to using anywhere near full capability. Which of course leaves the dp1, with 30% less weight and AWD... :) I think Bikini will be a nice set of training wheels for that. And speaking of dp1, there is good progress on the production chassis and some interesting aerodynamic developments. Should do an update one of these days....
01/2//07 Some more progress on getting Bikini ready for spring. Mostly spent the day fabricating various plumbing fittings - both oil and water. Laborious but hardly picture-worthy at this point. They will be once installed. I did figure a lot of it out - the various parts I still need, where the electric water pump is going to go, how the oil lines will connect to the oil cooler, etc. More of the same tomorrow.
One visual thing I did was test-fit the rear body panels on the car now that the exhaust is sort-of in. The rearmost 'tea tray' would have to be cut pretty extensively so I might as well just leave it off - it's not like it does much anyway except restrict access. Besides, the mechanicals under it are neat looking and will be even more so once throttle bodies are on.
The exhaust does clear the main panel pretty nicely, as if I had intended it that way (in truth this is just a happy coincidence, I did not have any dimensions for the body panels when designing the exhaust figuring that they're easy to cut if need be).
Yeah I think I like it this way. Now, back to more detail work. So much remains. Good thing I have another two months before the first trackday of the year.
02/17/07 I've been busy with work projects lately which is setting the car efforts back some, but today I made it a point to do some work on Bikini. The plumbing is a continued challenge, with much fiddling, hunting for fittings, hoses, clamps, etc. The good thing is that much of what I learn here will apply directly to the production dp1. One thing that won't apply, but needed figuring out anyway, is modifying the oil tank to fit. I was trying to come up with all kinds of fancy ways to indent it for frame rail clearance. Then I decided to just try a hammer. If it didn't work I could always go the cutting-and-welding route. To my great relief, the hammer worked well and it was pretty easy too. You can see where the dent fits the frame.
So now I just need a couple fittings, a manifold of some sort to join the output of the scavenge pump stages, some clamps and a lot of patience. Oh, and I need to design and fabricate oil tank mounting brackets but that's already done in my head, just need to do it in SolidWorks.
Another thing I did today is experiment with placement of AirTabs. The ones I have placed so far all serve to reduce drag. The attempt to produce downforce will come later, after I've run it as-is.
Of course drag reduction is not all that important when you've got over 375hp on tap, but what the heck. It's one of those things that's fun to play with because it's easy, cheap and visible. On a side note, after seeing the AirTabs on DarkHelmet, my friend David said he'd be ashamed to be seen in that car. I guess this means he won't be asking for a ride in Bikini either ;)
03/15/07 Even though it's been almost exactly a month since the last update, I've actually been working pretty diligently on this beast for the last week or so. The task at hand is plumbing and it's a major pain. The drysump scavenge circuit in particular - there are three scavenge stages, two are manifolded internally into a -12 outlet, the third is by itself with a -10. So the outputs have to be brought together in a very confined space into a single -12 line and then connected to the aluminum pipes that run in the chassis to the forward-mounted cooler. I'll need to do more exhaust shielding where the line exits the manifold. Also, while the Aeroquip push-lok fittings may sound cool (just push the hose onto the barbs), the reality is that they are a major pain. The smaller -10 stuff I managed after a few attempts, but the larger -12 was a definite no-go. I got Joe to stop by and asked him to try. He tried for about half an hour and came to the same conclusion. So I took it back to Oil Filter Service, the shop where I get all this stuff, to have them do it. No problem, took all of 5 minutes. I asked if they have a tool or machine for it. "Nope, we do it like the customers do, by hand. We're just used to it". Hmm... These guys must work out a lot. Well, got it done and that's what matters. In keeping with the tight clearance theme, the line from the filter to the engine clears the CV joint by 1/4" or so. It does clear, so as long as it doesn't move when pressurized I'm good.
And of course since the cooler is used by Brammo as a supercharger intercooler (filled with water), their standard hoses are not oil-compatible. So I had to figure out how to make the connection from the pipes to the cooler as well. Ended up ordering some tight mandrel-bent 90 degree aluminum sections then attached with pieces of hose. Expensive and fiddly but it'll work. There's over $500 in plumbing on this car. The dp1 installation of the V8 will have to be a cleaner, simpler design. But at least there's progress here now, the plumbing is nearly done. A couple oil fittings remain, some water stuff, oil tank mounts need to be designed and made and coolant overflow tank needs to be sourced. A couple solid days should take care of it.
Also got the clutch line hooked up. The MTX gearbox has an internal slave cylinder with a weird fitting. So I had to buy a Ford clutch line from the dealer, cut it in two, then put a standard fitting on it and got it flared. The line is very thick-walled so the flare didn't work very well. Hopefully it won't leak, otherwise I'll have to re-do it differently (still have the other half of the clutch line just in case).
Besides finishing the plumbing there's still the matter of the shift linkage and of course the electricals. Does not look like I'll make the Alfa day on the 24th, but it's just as well. I'll spend next week getting the dp1 proto ready for more testing - there's quite a list of items to do on that too. In the meantime, with the throttle bodies installed and throttle cable hooked up, Bikini is looking more and more complete. I'm quite excited - this thing is going to ROCK :)
Before too long, I'll be playing Dr. Frankenstein again :)