16 June 2018

Finally swapped in the Inconel turbocharger mounting studs. Hopefully this stomps out that failure mode for good.

I also had the pleasure of again meeting Martin Waide at a dinner party, ex-Lotus engineer from back in its heyday.  To talk to someone who worked for Colin Chapman himself,  and with Graham Hill and Jim Clark, is just, wow, expanding my world while at the same time making it feel a lot smaller. It’s like finding a little window through which to peer back into history, marveling at the golden age of racecars.

He asked many questions about Midlana and not unexpectedly, surrounding guests rolled their eyes and moved away as we went into suspension design. Since car design is such a niche, I don’t discuss it much because I know that it’s not at all interesting to most people, but, get me in the same room with someone who works in the field and off I go.

I’m going to meet up with him again so that he can check out Midlana; not as “look what I did” but to get a real engineer’s perspective on its design.

7 July 2018

Still here – building a cover over the pond filtration and wiring it with proper GFI outlets instead of the spider web of extension cords I had before. That’s done, but work on the car is postponed due to the first heat wave of the season; it’s currently 101.8F outside and high 90’s in the garage. Just before dawn it was 75F, hah.

On the car, the cold air (hah) intake, wings, and engine cover remain to be done. There’s a driver’s school in September which got my interest because they claim they’ll be running a large-diameter wet skidpad, something I’ve always wanted to run Midlana on (though it means me and the car getting drenched). With all the recent changes (engine, turbo, tune, transmission ratios, differential upgrade, shock settings, and new tires), Midlana’s capabilities cannot be  legally and safely tested on public roads. I say they “claim” they’ll be running it because having water trucked in for the purpose is reportedly around $800, so I want to make sure they’re really going to do it before signing up. An inquiry was sent but I’ve heard nothing back – what a surprise*.

Other odds and ends: Adding the engine tray has aerodynamic advantages but carries with it other consequences. The most striking is that both oil and coolant temperatures increased roughly 4 deg C after adding the undertray, so convection cooling through the engine compartment was measurable. I imagine it’ll be even worse once a new engine cover is installed because the only cooling air will be coming in the side vents (the right-hand vent is currently non-functional but will be cut open). There is some concern that convection and ram-air effects may not be enough to keep things under control, so Plan B is being considered: an engine compartment cooling fan. I remember reading something interesting about the development of the McLaren F1, where they had similar engine compartment temperature issues. The most interesting aspect was where they mounted them: flat on the floor, sucking air upwards into the engine compartment. This had the double effect of moving air in the direction it wants to go anyway (hot air rises), but most importantly, lowered the pressure under the car by a measureable amount, thereby increasing downforce (or decreasing lift) at the same time. That’s pretty clever. The downsides I see are that dust and dirt kicked up by the front tires is likely to get sucked up, plus, the highest ambient temperatures is located closest to the ground. Granted, it’s (probably) cooler than the air around the engine, but I’m not sure whether it would work as well here in Southern California as it might at McLaren’s home of Woking, UK! Effectivity aside, finding space for it could be a challenge, as there’s just not that much open space anywhere in the engine compartment – whoever designed this didn’t oversize things much!

*This is a continued irritation with me, vendors that sell a product yet make it difficult or downright impossible to give them money. I’m currently designing a new pond filter which uses “feather rock”, a volcanic stone with interconnected pores. We have a local distributor of the stuff and I’ve called or walked in four times now, trying to get them to tell me if they can get the stuff – I know they can since they already sell the boulders, which come from the same mine, but I want the 2″ stuff, but the vendor just won’t answer my questions. As a last try, I’m contacting the mine directly and will ask them if they can kick their local distributor in the nuts to make them answer me. Best of all would be for the mine to offer and sell it to me and ship it with the boulders next time they make a shipment to my local outlet, then I pick it up there. I would enjoy walking in and asking for status, and after they give me another non-answer, I say “I’ve done all your work for you; here’s what’s going to happen.” Apparently business is so good these days that vendors just don’t want to bother with special orders – fine, but they could at least say so!

18 June 2018

Had a brief dream of backing Midlana off a trailer and realized there’s a problem, in real life as well – that unless the angle is very mild, there’s a fair chance the diffuser will drag. Have to take some measurements before that happens.

On a related note, I found an unintended airflow experiment has been going on. Back when I replaced the turbocharger studs (more on that in a moment), the turbo oil feed line and feed adaptor had to be removed. It leaked a little and dripped onto the diffuser near its front center. Because of the way the diffusers attaches, some of that oil ran to the forward edge and got caught up by the air flowing under the car. The cool part – which looks better than the picture – is that the air flow remains well attached as it flows aft. What’s hard to see is that near the front edge, the air flows in and sort of “funnels” into the center channel of the tunnel, showing that the strakes are working as well. Also, along the top edge of the picture, you can see how the air flowed up onto the frame/Gurney flap, which would be expected if it was doing its thing. Good.

Regarding the turbo studs, after doing some more reading and getting some helpful hints on the Midlana Builders’ Forum, it was decided that they’re being replaced again, with the only type of stud that won’t stretch under high heat – Inconel. Actually ordering them though was a bit of a drama. For whatever reason, they’re fairly common in the aftermarket – in Australia – but not so much here. Testing the waters, I found they wanted about $50 shipping for their $50 parts, so no go there. In short, they were found domestically in a somewhat-surprising-but-shouldn’t-have-been source, Mazda. Seems the factory had such serious problems keeping their turbos attached to the second(?) gen RX-7, that they use Inconel studs. Thanks somewhat to mass production, they’re “only” $12 each, but hopefully once they’re in, that’ll be the end of that.

As an aside, a vendor in the US advertises “Inconel” studs, but reading the fine print, it turns out they’re actually “Incoloy”, which research shows isn’t the same thing. The vendor tried convincing me they were and that Inconel is just a brand name of Incoloy, yet research seems to indicate that Inconel has more nickel in it and is quite a bit more expensive (less profit). We use the material at work for really high temperature applications and use Inconel and nothing else, so there.

Lastly, if someone tries selling you fasteners and claims they’re Inconel, a simple test is that they will look like ordinary steel (not stainless) but are non-magnetic.