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My build has finally progressed to the point that I thought I would share some pictures. I started with the basic book frame design and redesigned it for IRS, inboard rear brakes and chain drive. I am using a 2002 R1 engine. The chain drive allowed me to offset the engine to the side opposite the driver for better balance. In this position the header exits to the passenger side and away from the passengers feet (and especially mine!). This position also allows the engine bay to be fully triangulated, top and bottom. Two shorter chains are used with an idler sprocket located midway between the Diff and engine. This idler sprocket adjusts fore/aft to tension the front chain and the rear chain is adjusted with a conventional tensioner. I used Miata spindles and uprights as well as a shortened Miata steering rack. The pushrod suspension uses R1 spring/shocks and rockers to achieve a 15-20% progressive spring rate. I was hoping to keep the weight to about 850lb dry but I piled all of the bodywork and misc components on the car and weighed it right at 900 lb.
I think I am pretty well done fabricating so now it is mostly assembly. I hope to have it on its wheels bythe end of the month and roadworthy by Labor Day.

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Mike Stieff

Looks great!

You dawg...keeping your build under wraps until now!

Looks great. I can't wait to see more. Don't be afraid to post larger pictures...I think about 800-1000 pixels wide is ideal for these build logs. Otherwise it is very difficult for us to steal your ideas.

Your headers are a work of art! They'll look awesome when you get the bodywork on. 900 pounds doesn't sound too porky to me.

Keep up the good work,
-dave

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...nowadays people are so intellectually lazy and lethargic that they can't build ANYTHING with their hands. They'll spend hours watching whiny people marooned on an island, but won't spend a second adding anything to the world. -weconway
Visit my [Locost 7 build log]

Nice work there. Unique setup! Keep the pictures coming
Rob

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Locost complete! Yamaha FJR1300 BEC

Nice work. Show us more.

Any chance of sharing the spec on your header?

Andrew

Must...resist....BEC...

Seriously, that's incredible. You've got to have more to share than that!

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William Conway
Building the Spartan 7 - Build Blog
LocostUSA Build Log
How do you eat an elephant? One bite at a time...

That header is sexy.

Keep us updated!

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JSullivan

Nice work. Would you be willing to share a bit about your diff and what sort of driveshaft system you will be using/adapting to the Miata uprights?


Thanks

Brian

Thanks, Here is a link to these pictures in higher resolution:

http://usera.imagecave.com/mstieff/Locost/

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Mike Stieff

Thanks, The headers are basically the same length as the stock headers. the primaries are equal length (~24"). They are made of stainless steel. I designed them (and much of the rest of the car) on Pro-e so I can provide a CAD model if you can use it. I'm a novice welder so I had a co-worker weld them up for me after I cut all of the tubes to length.

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Mike Stieff

Thanks, The headers are basically the same length as the stock headers. the primaries are equal length (~24"). They are made of stainless steel. I designed them (and much of the rest of the car) on Pro-e so I can provide a CAD model if you can use it. I'm a novice welder so I had a co-worker weld them up for me after I cut all of the tubes to length.

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Mike Stieff

Thanks. The Diff is based on Miata internals. I removed the "innards" of the differential from the housing, removed the two tapered roller bearings and replaced them with ball bearings. The ball bearings are then supported in hubs attached to two aluminum plates mounted to the sides of the "tunnel". The "tunnel" is just an extension of the tunnel running through the passenger compartment but a little heavier gauge (.059" as opposed to .047"). The crown gear is removed and replaced with a sprocket. An aluminum "can" was made to cover the holes in the carrier portion of the diff to keep the oil in. The D sports racer guys do something similar with their differentials. The halfshafts are then just shortened (-2.09") Miata parts.

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Mike Stieff

sweet build....first locust i have ever seen with a engine perpendicular in the front.....I am planning on doing something similar in the rear with a diff and inboard brakes, but I probably am going to use 2 discs, one on each cv, my car is going to be a middy tho....

hope to see....and hear the car running in a future video.....

keep up the good work

A couple questions:
What's the front and rear wheel rates?
What's the front and rear suspension travel?

Reason I ask is because I tried using bike shocks, but starting with 1.5" travel and 600lb spring rate and couldn't achieve a usable wheel rate and retain good suspension travel. Since I wanted 6" wheel travel, that's an installation ratio of 4:1. That means I'd need a crazy-high spring rate - 16 times the wheel rate. This is why I'm interested to know what you did.

Do you expect oil leakage from the diff as the air inside heats up, expanding and pushing the oil past the seal?

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Midlana book: Build this mid-engine Locost!, http://midlana.com/stuff/book/
Kimini book: Designing mid-engine cars using FWD drivetrains
Both available from https://www.lulu.com/

Front Wheel rate is (from memory) 75 lb/in with the rear being 80 lb/in. I approached the wheel rate from a different direction based on my experience with my '70 Europa. That car had 100 lb/in front and 72 lb/in rear spring rates. in stock form. I increased the stiffness approx 40% for autocrossing but I didn't like what it did to the ride quality. My Locost will be (realistically) driven much more on the road than on the track so I erred on the side of ride quality. I also went with urethane bushings on one end of each wishbone with Heim joints on the other end for the same reason. The rear suspension geometry of the Europa and my Locost are very similar so I felt that going with similar spring rates there was a good starting point. The Europa is also a relative porker at 1450 lb vs 900 for my Locost so I still expect the locost to be tighter than the Europa. The R1 springs have a rate of 510 lb/in and 2 inches of travel before they hit the bump stops. My rockers have a ratio of approx 2.5/1 resulting in almost 5 inches of travel once all is said and done. I figure that stiffer springs and roll bars are available for tuning if required as are different rocker ratios.

You have keyed in on an area of concern that I too have with the diff. I designed the can that encloses the diff with o-ring seals so I don't think it will leak there. The problem (if there is one) will be at the axles. I designed that with lip seals that are supposed to have some low pressure sealing capability but I really don't have any experience with them so we'll see. At least one DSR guy claims that the diff can be pumped full of grease to help it all stay put. The DSR guys have figured this out (or clamed to at least) so It shouldn't be impossible to sort out. If not I'll just say it's basically a British car and that you should expect it to leak.

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Mike Stieff