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 Post subject: Rumbles Tiger 700 Build
PostPosted: May 12, 2017, 11:49 am 
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This thread will be the build log of my Tiger 700. This is a continuation of my "Rumbles Extreme Build" thread in the Locost Bike Engine Build Forum. In my Rumbles Extreme Build thread I examined previous motorcycle engine powered vehicles and debated which type of car I would build. Now that I have decided to build the Tiger 700, it looks like my log fits better under the Non-Traditional Builds Log forum.

I'm re-posting my last entry (below) from the Rumbles Extreme Build thread just to kick it off here.

Its official...I have begun my own Locost build! When I say "its official", I mean that I'm now committed, have an initial design, and have started buying the components.

  • It will be built using many of the techniques I've learned on this Locost forum, as well as the many "Build a Sports Car Cheap" books (I read them all).
  • It will be about the size of a coffin.
  • It will be powered by a motorcycle style engine (kinda)
  • It will weigh more than a ATV, but less than a Harley Davidson
  • The body will take styling inspiration from the Mezzerschmitt TG500, Rat Rod VW, quarter midget racer, the Indy STP turbine car, and the wind scarf of a World War One fighter pilot.
  • It will be stupid fun!

I have been lurking around this forum for a while trying to absorb all the knowledge / techniques you share with each other. I also look to the past to understand the design aspects of bike engined cars that were successful and those aspects that just didn't work. Finally, I look to the present for proven car building techniques, as well as high tech aircraft approaches that are now becoming practical for the hobbyist car builder.

A little about me

I'm a shade tree mechanic from way back. It all started with muscle cars in high school and now my more recent efforts have been building a couple kit cars. The kit cars taught me building techniques that I hope to use in this project.

Ever since I was a pimple faced adolescent boy, I always wanted to do a blank sheet design for a light weight car and then build it for street use. Now is that time!

Below are my last 2 car builds.


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PostPosted: May 12, 2017, 12:42 pm 
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It's funny that you're coming from building a (probably V8-powered) IMSA type kitcar and going to a Locost. I'm sort of the other way around, wanting to build something like that very kitcar but am stymied by the high cost.

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Kimini book: Designing mid-engine cars using FWD drivetrains, http://www.kimini.com/book_info/


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PostPosted: May 12, 2017, 12:59 pm 
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Tell us more about the yellow one. Is the red one Factory 5?


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PostPosted: May 12, 2017, 2:01 pm 
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I'm sure the yellow one is this: http://www.superlitecars.com/slc/

When all done figure around $80-120K...

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PostPosted: May 12, 2017, 2:29 pm 
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From the name, you can probably guess the Tiger will be powered by a 700cc motorcycle type motor. But I am taking a slightly different approach. I will be using a Yamaha Raptor 700 ATV for my donor. The Raptor 700 is about the most powerful and fastest ATV on the market. They can do 80mph straight from the factory on trail tires and using trail gearing.

There are some Pros and Cons for using a Raptor 700 ATV vs motorcycle donor.

Pros
  • The ATV motor builds torque at lower RPMs. Superbike motors tend to make their power at high RPMs, and that presents drivability issues.
  • The ATV oil pan is designed to prevent oil pump starvation as oil sloshes when cornering. A Superbike motors assumes you will lean into corners and thereby keeping the oil at the bottom of the pan. Superbike motors are generally tall with a deep oil pan. To lower the center of gravity for a 4 wheel vehicle and to minimize oil pump starvation, the oil pans should be modified.
  • The Raptor 700 transmission includes a reverse gear. This is a huge advantage since no after market external reverse mechanism needs to be added.
  • The ATV comes with many of the chassis and suspension parts that can be used in the final vehicle. This will save much $$$.

Cons
  • There are no ATV motors larger than 700cc. So it will not have the exciting peak power of a Superbike motor.
  • The Raptor 700 is a single cylinder motor, so there will be more vibration.

Vehicle Design Goals
  • Given the limited engine power and the chassis/suspension max weight limit, the final vehicle will be an exercise in light-weight engineering. The goal is to keep the final curb weight to about 550lbs. As a result, the size of this vehicle will fit into the Micro-car category.
  • It will be a street car. It will spend most of its time on urban (30-45mph) and secondary country roads (45-55mph). I want to be able to drive it on limited access freeways as well (65-70mph). The top speed should be about 100mph.
  • It will be large enough to carry 1 full size male in comfort and have space for a little luggage.
  • It will be fun to drive, safe, simple to maintain, and cheap to keep.

Below is a photo of the donor


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PostPosted: May 12, 2017, 3:21 pm 
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If you are going the ATV engine route then there are a plethora of other donors that aren't single cylinder in the UTV catagory. many with much more power, and a reverse gear

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PostPosted: May 12, 2017, 3:34 pm 
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John Hancock wrote:
Tell us more about the yellow one. Is the red one Factory 5?

Thanks.

The red 1933 Ford 3 window coupe is a Factory Five car. It is powered by a Ford 32 valve, double overhead cam modular V8 and a AODE automatic transmission. It was an 18 month project. It weighs about 1700lbs and was great fun to build and drive. In fact, I drove it 2600 miles on the 2012 Hot Rod Power Tour from Charlotte NC to Dallas TX and back to Charlotte NC again. I have plenty more photos in my '33 Hot Rod online library.

The yellow car is a SuperLite-Coupe (SLC). Its basically a kit race car that I built and adapted for street use. It has a race proven aluminum chassis, custom aluminum suspension, coil-overs on all 4 corners and a race weight fiberglass body. Its powered by a GM LS3 and a 6 speed Getrag G50-20 transaxle. It was a 36 month project and weighs about 2600lbs. The prototype for this car (same chassis & powertrain) had quite a racing history. It won every race it finished, set numerous track records and ultimately won the NASA Unlimited class in 2012. I like to say my SLC is built nearly the same, except I have a nice interior:lol: You may have recently seen me and my SLC on the Gearz show on the Velocity channel. I also recently finished a video session at RTM productions studio in Nashville that will feature my car and me on the Velocity channel's Power Nation. It should air some time this Summer.

Here are a couple of my homemade videos

I have plenty more photos in my SLC online library

If you want to dive into the nitty-gritty details, I published a detailed build journal for each of the cars. All together, there's over 600 pages and 400 photos of assembly, fabrication, part numbers, etc. You can find both of them on Amazon by searching on "Car Builder Journal"


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PostPosted: May 12, 2017, 3:37 pm 
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Total expense was?

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Kimini book: Designing mid-engine cars using FWD drivetrains, http://www.kimini.com/book_info/


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PostPosted: May 12, 2017, 3:43 pm 
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carguy123 wrote:
If you are going the ATV engine route then there are a plethora of other donors that aren't single cylinder in the UTV catagory. many with much more power, and a reverse gear


Yup, I looked at UTV donors as well. They have many of the same advantages as ATV and some of the sport models have powerful engines that are pretty quick. The problem is that they are geared for trail use and have gear/shaft driven power trains that are difficult or expensive to change for highway speeds.

You might be able to use a UTV donor if you go with a large diameter wheel/tire package. In other words, Dub your UTV :-)

Image


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PostPosted: May 12, 2017, 9:57 pm 
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The UTVs I've seen had CVTs which would have been rather simple to change ratios. I haven't looked at all that many, but the 2 I've had were that way too. Now some of the newer bigger ones have gears and everything so maybe they "improved" them.

I drove the big Polaris recently and it went like stink, they said the top speed was in excess of 100, but I never looked under the hood.

I sat in your Coupe, or one exactly like it, when the Power Tour was in Dallas. That means I probably talked to you too. Small world.

I also lusted after your SLC on Gearz.

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PostPosted: May 13, 2017, 10:05 am 
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carguy123 wrote:
The UTVs I've seen had CVTs which would have been rather simple to change ratios. I haven't looked at all that many, but the 2 I've had were that way too. Now some of the newer bigger ones have gears and everything so maybe they "improved" them.

I drove the big Polaris recently and it went like stink, they said the top speed was in excess of 100, but I never looked under the hood.

I sat in your Coupe, or one exactly like it, when the Power Tour was in Dallas. That means I probably talked to you too. Small world.

I also lusted after your SLC on Gearz.


Wow, 100mph UTV!

I did shy away from donors with a CVT. I worry that a CVT belt would wear out pretty quickly on long stretches straight freeways.


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PostPosted: June 6, 2017, 12:44 pm 
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I have made some progress on the design of my Tiger 700 build.

I started by reading several books on the car design process. One of the most informative books was a text book used in the ArtCenter College of Design. The the ArtCenter College of Design has produced many of the great car designers of our time, such as Chip Foose, J Mays (Head of GM Design), Camilo Pardo (Ford GT designer), etc. The book title is "H-Point, The Fundamentals of Car Design and Packaging" by Stuart Macey. The book shares the basic process to follow when designing a car concept. H-Point says you should start from the inside out, by first considering the what the vehicle will carry, i.e. passengers and cargo. In my case, the Tiger 700 will just carry 1 adult, and very little cargo. The car will be a day cruiser, so all I need to carry is a small tool bag, a jacket, and lunch.

H-Point also include many SAE design rules of thumb and it pointed me to the SAE dummy manikin used by all the major car manufacturers. The SAE manikin measurements represent the proportions that fit 90% of adult drivers.

My first drawings below a very basic start of the concept (no laughing please) :lol: . Since it needs to a very light weight car, the concept has minimalist proportions. The next step is to refine the design by sculpting a clay model.

Top View
  • The narrow rear track with is unchanged from the donor, because it is a live axle with no differential. If I made it wider, there would be more tire scrubbing in the corners. I plan to use narrow 14" tire to allow some scrubbing. These narrow 14" tires are cheap so replacing worn tires won't be a big deal. I'll just consider them a wear item.
  • The front track width is considerably wider than the rear. That provides greater stability and more leverage to overcome the rear scrubbing.
  • The body shape is narrow to fit 1 adult, but it also has an overall tear drop shape. The teardrop shape is meant to compliment the wide front and narrow rear track widths.

Side View
  • I used the SAE 90% manikin and the Raptor 700 power-train to layout the minimum wheelbase.
  • The sides come up to the top of the mankin's shoulder for additional protection. The high sides also provide a sense of security inside the cockpit.

Front and Rear View
  • The front design is going for a "It's so ugly, it's cute" look.
  • I want it to look like its simple fun to jump in and drive


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Concept Drawing side view.JPG
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PostPosted: July 3, 2017, 9:48 pm 
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Its been a while since my last post, but I have been making progress.

After the simple line drawings, the next step is to refine the exterior shape with a clay model.

But first, I need to introduce my new partner, "Maple" the super-model. Maple has graciously accepted my invitation to help in the clay modeling phase. She has vast experience in the art modeling business posing for literally thousands of artists. Maple is quite expressive, but can be a little stiff at times until you get to know her.
Image

One of Maple's greatest talents is that she is exactly 12" tall, which is 1/6th the size of an average to tall male. By building the car in 1/6th scale, Maple (the Super-Model) will help me refine the cockpit sizing and placement of controls.

Building the 1/6 model required a few steps:
  • I started by printing my simple line drawings in a 1/6th scale and attaching it to a wood base.
  • I then attached a wood spacer that approximates the ride height of the car.
  • I then placed the car floor on the spacer and fabricated a plywood frame for the clay to cling to.
  • Then the clay is crammed on to the plywood frame so it is a bit larger that the car will be.
  • I used a machinist square to cut markers into the clay that follow the outline of the line drawings. Those markers served at sight lines that allowed me to carve the excess clay away. That gave me a squared off model to start off with.
  • Then the actual sculpting begins. Trying different shapes, body lines, and getting the proportions right. As you might guess, this step of refinement changed the original line drawings a bit.

The end result is a 1/6 model that is 19" long and weighs a hefty 35 lbs.

In my next post, I'll share the finished 1/6 model.


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PostPosted: August 14, 2017, 6:33 pm 
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I have completed the initial 1/6th clay model. This model will be refined as I work thru each of the downstream steps of the design.

I have actually made quite a bit of progress on the downstream design steps. Some of the refinements not shown in the pictures include an overall lower shoulder line and larger headlights.

To see a video of the clay model -> Click here

In true Locost fashion, I avoided every expense possible in this model:
  • $6 - The wheels are made from PVC plumbing drain grates. I then printed the wheel/tire covers and used black tape on the circumference
  • $0 - I used a hole punch to cut the lights from a ABS plastic sheet that came from a disposable shopping bag
  • $0 - The roll bar is some aluminum rod I had laying around that I bent into shape
  • $0 - The windshield posts are some 1/8" aluminum bar I had from a past project that I cut and shaped.
  • $0 - The windshield glass is some clear plastic I cut from the packaging of a tool I bought.
  • $Priceless - Maple the supermodel


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PostPosted: August 20, 2017, 5:45 pm 
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You might be wondering what I was smoking when I designed the Tiger 700 :drool:

The main inspiration was the Messerschmitt TG 500. Messerschmitt was an aircraft manufacturer during Word War II. Part of Germany's surrender agreement was that they would not produce any aircraft for ten years after World War II, so Messerschmitt retooled to produce a small 3 wheeled car that looked like an air plane without wings. When they added a 4th wheel, the TG 500 was born. The TG 500 was manufactured from 1958 to 1961 and was nicknamed the "Tiger 500". With a 500cc engine, the TG 500 was considered a performance car in its era.

Think of what I'm building as "Hot Rod Messerschmitt". In true hot rod fashion, that means you tear off the fenders, install larger wheels/tires, put a more powerful engine in it, and make it lighter.

The design takes inspiration from other cars as well:
  • The front fascia barrows elements from a Rat Rod VW Beatle
  • The heat chimney behind the driver's cockpit is reminiscent of the STP turbine race car that ran at Indianapolis.
  • The tail cone is from a vintage indy car of the late 1950s.

Before I started the design, I read a book called "H-Point: The Fundamentals of Car Design and Packaging. This is a text book used in the prestigious Art Center College in Pasadena CA. The Art Center College produced many of the greatest car designers of our time such as Chip Foose, Ed Welburn (GM VP of Global Design - Retired), Camilo Pardo (designed the Ford GT).

Anyway, the H-Point book was a great starting point with lots guidance on packaging. It recommends designing a car from the inside out. So I started with the ASE manikin template, which is the auto industry's standard that represents the human body dimensions for 90% of the population.

The body pays homage to the TG 500, but is a unique design (not a replica). The overall body dimensions are close to the TG 500, but not a single panel is the same.

Oveall, the design theme is to make so ugly its cute, like a VW Beatle, Fiat 500, or MG Mini.


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1968 Granatelli STP Turbine Indy car exhaust.jpg
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vintage indy car tail cone.jpg
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