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PostPosted: August 3, 2017, 10:59 pm 
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Hi all,

I thought here would be a good place to start a thread as place to gather information and keep track of progress on my final year design project (aka thesis) for my Motorsports Engineering degree at Oxford Brookes. I'd been toying with idea since last January, and happily the project was officially accepted last semester. I would love to see the modern day "microcar" make a comeback in a small, lightweight, sporty, practical, and cost-effective package. I've been looking at various motorcycle engines (and the 1.0L Ford Ecoboost 3-cylinder) as candidates. Currently have CAD models of Honda, Ducati, and Triumph engines. In fact, I will likely "borrow" the engine from my beloved 955cc Triumph Daytona to power the first prototype, which is why I chose to stick the thread in this forum.

I'm filling out the CAD model pretty well; what began as a conceptual design and packaging study has evolved into a pretty large file with all major vehicle components, and right now I am looking around for more engine dimensions (and hopefully CAD models) of the Triumph 1200 triples, Honda VFR, and BMW S1000RR engines. I've been using a scaled-up Triumph 675cc motor for basic dimensioning because that was the only triumph motor CAD model I could find.

Obviously, a big part of the question for me is whether a transverse shaft driven motor or a longitudinal chain motor is better.. Right now I plan on starting with my Daytona engine mounted longitudinally, but I would like to be able to accommodate both.

Some key design parameters: The goal is to design a modern day "micro car" (just a very small car) that can comfortably seat two 95th percentile males (6'1", 225 lbs), offer more trunk space than a Smart car, Mini Cooper, or Fiat 500, etc, outperform more than a few sports cars sports, and introduce a new generation to the idea of lightweight, fast, and economical motoring.
- Engines ranging from 120-200 hp motorcycle engines
- Elite Racing Transmissions MX200IL limited slip differential unit with integrated reverse gear
- Double wishbone front & rear suspension
- Fiberglass Body
- 1200-1600 lb target weight depending on trim, max performance variant approximately 325hp/ton
- 40" tall
- Sub 2 meter wheelbase
- Everyday usability in an attractive package


The focus on my thesis will likely be the design and development of crash structures in ultracompact vehicles; as you can see in the to-scale pictures below, a car this small needs to offer seriously good crash protection. The project will be developed with a theoretical production model in mind, with an estimated base price starting around 14,000 EUR/ 12,000 GBP (such a car would have a much larger market in Europe). Hopefully this provides some entertainment in addition to everyone as well as general information. Enjoy; all questions are welcome!


The tubeframe will be steel alloy and weighs just under 100kg with a torsional stiffness of 20,000 N.m/degree


I'm trying to place every large or heavy item to progress on packaging and get an idea of static weight distribution. I'm very pleased with the numbers so far, looking at wet weight estimate of 1267 lbs with a 49:51 F/R weight distribution. Center of gravity is about 15", or 2.5" lower than a Tesla Model S and Ford GT. Tonight I modeled/sourced CAD for a battery, radiator, and various other suspension components... If anyone thinks of anything I missed let me know!


Last edited by sbeckman7 on August 18, 2017, 2:05 am, edited 2 times in total.

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PostPosted: August 4, 2017, 12:37 am 
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How do the doors work given that it's tube-frame with side bars? Do the side windows have glass? Just saying that on the one hand it's being presented as a true road car but seems to be a GT race car in execution. Nothing wrong with either but achieving both isn't realistic in this context. You pretty much have to decide whether it's going to be a race car OR a road car (doors, glass, heat, A/C, etc). At our end of the pool we just don't have the ability ($$$$$) to create something that's both. And don't take my comments personally - I rain on everyone's parade.

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Last edited by KB58 on August 4, 2017, 9:15 am, edited 2 times in total.

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PostPosted: August 4, 2017, 12:53 am 
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Hi sbeckman7, welcome aboard.

Would you mind going back to your original post and narrowing* the pics? As it stands, that post is a couple of screens wide and scrolling side-to-side to read your text is challenging.

*By at least 50%. See other topics on this forum; most of their pics max out at 800 pixels wide.

[EDIT--examples added. Also I wanted to tip my hat to your graphic design skills.]


Attachments:
File comment: Here's your 2409 x 1209 pic, cropped to 1600 x 1200 and shrunk to 800 x 600
MicrocarShrunkBy2.jpg
MicrocarShrunkBy2.jpg [ 58.4 KiB | Viewed 307 times ]
File comment: Here's your 2409 x 1209 pic, cropped to 2400 (thus retaining the artistic white space front and rear) x 1200 and shrunk to 800 x 400
MicrocarShrunkBy3.jpg
MicrocarShrunkBy3.jpg [ 31.87 KiB | Viewed 307 times ]

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Last edited by JackMcCornack on August 4, 2017, 1:13 am, edited 1 time in total.
I thought examples would be useful.
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PostPosted: August 4, 2017, 10:58 am 
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This is a very interesting project. It will be fun to follow. Best of luck with it.

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886


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PostPosted: August 4, 2017, 4:30 pm 
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Cool idea and great start on chassis, but how in all that's holy will you get in with the side bar AND a roof?

But if the bar goes lower how will you gain torsional rigidity?

Big issue with all BEC is reverse, so what are you going to do about that?

Well and super light flywheel and bottom end strength to allow a larger flywheel

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PostPosted: August 4, 2017, 4:43 pm 
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carguy123 wrote:
Cool idea and great start on chassis, but how in all that's holy will you get in with the side bar AND a roof?

But if the bar goes lower how will you gain torsional rigidity?

Big issue with all BEC is reverse, so what are you going to do about that?

Well and super light flywheel and bottom end strength to allow a larger flywheel

I actually asked how people are going to get in - but removed it to not be overly negative. You're right about the BEC/reverse issue and it's yet another thing not acceptable in a road car, hence my comments about seemingly trying to have both a street and race car - I just don't think it's doable with today's definition of what a road car is. If your goal is building a "streetable track car" then you're fine - but I don't read it that way in your original post, especially the "...Everyday usability in an attractive package..."

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PostPosted: August 4, 2017, 5:26 pm 
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You will make your life much easier going down the small turbo engine route. GM have the 1.0 and 1.4 engines that are very common as well as lots of other engine options. In DMod Autocross the 1.4 turbo engine (Chevy Cruze) is the engine to have and the guys are getting close to 300hp out of it. They are small light and practical.

Bike engines are great for a light race car but as a production car there are too many issues to get past such as no reverse, oil issues when cornering (bike engines see minimal lateral loads as the bikes lean), low torque make it difficult to set off from the lights, transmission issues, etc.

I absolutely love what you are doing though. I think Micro cars are a great idea especially in Europe and the UK where there are lots of twisty roads. I look forward to following you progress.

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Scrap Metal Build Log viewtopic.php?f=35&t=14558


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PostPosted: August 5, 2017, 1:00 am 
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KB58 wrote:
How do the doors work given that it's tube-frame with side bars? Do the side windows have glass? Just saying that on the one hand it's being presented as a true road car but seems to be a GT race car in execution. Nothing wrong with either but achieving both isn't realistic in this context. You pretty much have to decide whether it's going to be a race car OR a road car (doors, glass, heat, A/C, etc). At our end of the pool we just don't have the ability ($$$$$) to create something that's both. And don't take my comments personally - I rain on everyone's parade.


I should have clarified a little more - this is the prototype and starting platform for what I would hope to evolve in to a production-ready version. Imagine the same car with an aluminum unibody construction (no need for tubeframe) and, unavoidably, an electric powertrain. For now I want to build a version with a motorcycle engine because an electric powertrain is cost-prohibitive, and I want it to be as exciting as possible. In this prototype version, the doors will hinge where the single diagonal tube meets the B-pillar, all windows will be lexan. The prototype will be more of a design study in terms of how small future cars can be while maintaining usability, and a production version would offer all the creature comforts one could expect in a car of that size and price range.

Nice to have a devil's advocate :wink:

JackMcCornack wrote:
Hi sbeckman7, welcome aboard.

Would you mind going back to your original post and narrowing* the pics? As it stands, that post is a couple of screens wide and scrolling side-to-side to read your text is challenging.

*By at least 50%. See other topics on this forum; most of their pics max out at 800 pixels wide.

[EDIT--examples added. Also I wanted to tip my hat to your graphic design skills.]


I'll get to work on that!

Lonnie-S wrote:
This is a very interesting project. It will be fun to follow. Best of luck with it.

Cheers,


Thanks, it has been a great challenge getting to this point and I look forward to the future as well!


carguy123 wrote:
Cool idea and great start on chassis, but how in all that's holy will you get in with the side bar AND a roof?

But if the bar goes lower how will you gain torsional rigidity?

Big issue with all BEC is reverse, so what are you going to do about that?

Well and super light flywheel and bottom end strength to allow a larger flywheel


Door will be as I mentioned above, yes it will decrease torsional rigidity somewhat but it's necessary for a production vehicle and I intend on making it as usable as possible. As for reverse, I'm planning on using the Elite Racing Transmission solution in the form of a differential/transaxle with built in reverse gear. Of course, I wouldn't have to worry about that with an electric motor ;) Bike engines in consideration are all 1 liter or above for the low-end torque that is necessary for moving 1300 lbs, but I think it will be sufficient as a starting point. The engines I'm looking at develop decent low-end torque.

wrightcomputing wrote:
You will make your life much easier going down the small turbo engine route. GM have the 1.0 and 1.4 engines that are very common as well as lots of other engine options. In DMod Autocross the 1.4 turbo engine (Chevy Cruze) is the engine to have and the guys are getting close to 300hp out of it. They are small light and practical.

Bike engines are great for a light race car but as a production car there are too many issues to get past such as no reverse, oil issues when cornering (bike engines see minimal lateral loads as the bikes lean), low torque make it difficult to set off from the lights, transmission issues, etc.

I absolutely love what you are doing though. I think Micro cars are a great idea especially in Europe and the UK where there are lots of twisty roads. I look forward to following you progress.


I've considered the EcoBoost and GM 1.0L motors (3 cylinders) but they're just too tall to fit under the hood right now. I looked at doing a mid-engined version with one of those engines where it would be a better fit but they also lack character and for me an ICE should be justified by the added excitement it brings to the car. A boring engine will be replaced by a motor for an all-electric future.

Thanks for the comments everyone! Cheers :cheers:


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PostPosted: August 18, 2017, 2:04 am 
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I will be visiting an electric motorcycle company in Santa Cruz tomorrow in the hopes of talking about getting motors and batteries for an electric version of the prototype. I am hoping the electric version would weigh less than 1800 lbs with 75 miles of range on a full charge. The current lightest electric vehicle, the carbon-intensive BMW i3, weighs 2600 lbs.

I also looked at designing a fastback/coupe body, and am finally learning how to model complex body surfaces in CAD (to be continued)! The coupe loses only 1 cubic foot of trunk space, down to 11.25 (still more than a BMW M Coupe, modern Mini Cooper, Fiat 500, Miata, etc.) but gains a lot in terms of aesthetic appeal for a wider customer base. I think the general public is much more drawn to coupes than hatchbacks in general.

I also created this little "quick facts" sheet on the high performance gasoline version to show to friends/people who may not know as much about cars. It outlines some key dimensions and my performance, efficiency, and cost targets for this version of the car. Like I said, I would hope a base model could sell for at least $10,000 less.

Image
Image
Image
Image
Image
Image
Image
Image
Image
Image[/url]


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PostPosted: August 18, 2017, 9:30 am 
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sbeckman7 wrote:
The project will be developed with a theoretical production model in mind, with an estimated base price starting around 14,000 EUR/ 12,000 GBP...

sbeckman7 wrote:
... I should have clarified a little more - this is the prototype and starting platform for what I would hope to evolve in to a production-ready version. Imagine the same car with an aluminum unibody construction (no need for tube frame) and, unavoidably, an electric powertrain.

This is entirely doable for Ford, GM, or more likely, an offshore mfg, but the price would very likely be more like mid-US$30K or so. I mean, compare it to any small/micro hybrid or all-electric car that's actually in production. I don't know of any mfg making a car in that price range and there's probably a reason. What's different about your design that lowers component costs by half?

As a "price point", someone can build the car I designed, "Midlana", for about US$12k, but only if they do all the work themselves and construct it with used parts. I don't see any "wiggle room" for a mfg to make a profit based upon the projected price above. I like everything you're proposing and think it's perfectly doable, but if I was a professor judging your design project, I'd be all over the cost projections - I guess I just can't see it as a viable product at that price point.

(This project also ignores safety - which mfgs absolutely cannot. Once airbags, crush zones, and door beams are added, the overall weight will go way up, hurting both performance and mileage.)

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PostPosted: August 18, 2017, 10:53 am 
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Kurt (KB58) above does have some valid points. However, much of the crash-worthiness could be overcome using structural foams within the bodywork. Years ago (perhaps 20 or more) a bunch of engineers came up with a safety concept for NTHSA that was very light weight, but also extremely crash worthy. I can't find a reference to it at the moment, but it's public research and there is a detailed publication covering it as well. I think the engineering firm that did the work was in Santa Barbara, CA.

It looks like you've done some thoughtful packaging work. If you don't know about it already, and I think you do, look up "H-Point 2nd Edition: The Fundamentals of Car Design & Packaging" on Amazon or similar.

Keep up the good work. If you're still a student, you're doing a lot of high quality work that can get you an interesting job.

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886


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PostPosted: August 18, 2017, 3:23 pm 
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The fastback reminds me of what you might get if you cross a TVR Garatura with a Saab Sonett.

I do like it.

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