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Author Topic: Bugatti Type 37 Build  (Read 31320 times)

ChrisS

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Re: Bugatti Type 37 Build
« Reply #135 on: 19 July 2020, 11:11:53 am »
What's your weight distribution like?  Mine is 70kg rear, 35kg front, so exactly 2:1.

RhysN

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Re: Bugatti Type 37 Build
« Reply #136 on: 19 July 2020, 02:43:10 pm »
At some point increasing tyre pressure = more grip, (somewhat counter intuitive) so may have added to the spoke issue, but also more rear grip would make the understeer issue worse.

StefanN

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Re: Bugatti Type 37 Build
« Reply #137 on: 19 July 2020, 03:54:44 pm »
What's your weight distribution like?  Mine is 70kg rear, 35kg front, so exactly 2:1.
89kg rear 42kg front, so overall a bit more portly but only slightly more rear biased than yours.

Also, from pictures it looks like I sit further back than you (and add more weight!)

StefanN

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Re: Bugatti Type 37 Build - tyres
« Reply #138 on: 22 July 2020, 09:13:51 am »
Ok, the whole tyre thing is getting more complicated... in theory
https://www.f1technical.net/forum/viewtopic.php?t=12762
Will be glad to try it out on the track.

RhysN

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Re: Bugatti Type 37 Build
« Reply #139 on: 22 July 2020, 11:00:23 am »
Interesting links, but are you really surprised? I could recite a lengthy story where the same size tyre from different manufacturers could make a difference of places in a race of several tens out of 50 odd competitors. Side wall flex, type of rubber, pressures are only some of the factors.
If it were simple then there would not be millions spent on tyre technology.
Once upon a time, not long ago it was considered that cornering or braking forces in excess of 1g were impossible. Now even non-aero cars are way above that.

StefanN

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Re: Bugatti Type 37 Build
« Reply #140 on: 22 July 2020, 11:24:46 am »
I’m only surprised in as much as I suspect that 90% still follows simple engineering principles and you only need to get into the details and nuances to extract the last 10% in more extreme performance than we hope for from cyclekarts.

I’ll mix in some experimental evidence and see what I conclude.

StefanN

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Re: Bugatti Type 37 Build
« Reply #141 on: 27 July 2020, 07:49:23 am »
Because it’s relevant to all cyclekarts and is likely to have quite a lot of discussion, I’ve moved the posts about the limited slip freewheel design to its own “topic” in the technical forum:
http://www.cyclekartsgb.com/tech-forum/limited-slip-freewheel/

StefanN

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Re: Bugatti Type 37 Build - Brakes
« Reply #142 on: 23 September 2020, 01:48:57 pm »
I realised that I didn't share my new brake set-up.  I went through a design process with the aim of having enough braking force to lock the rear wheels with a target foot travel and pressure.  So far I'm very pleased with the result.

0.7" Wildwood master cylinder from Rallydesign.co.uk http://www.rallydesign.co.uk/product_info.php?products_id=4052 £32
Front calliper from a 2007-2012 Suzuki GSF 650 Bandit £20 from a breaker on eBay.  The one I got was in good condition but you might need to replace seals on 2nd hand units.
Standard Gemini brake disc

The brake calliper has 2x 27mm pots and 2x 33m pots (CSA = 28.6 sq cm)

On no account should anyone be foolhardy enough to take any notice of what I've used.

StefanN

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Re: Bugatti Type 37 Build - handbrake and gear shift
« Reply #143 on: 06 November 2020, 06:41:31 pm »
Handbrake will be a parking brake, and haven’t decided what the gear lever will operate -  possibly choke or an air vent. 

StefanN

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Re: Bugatti Type 37 Build - Tacho update
« Reply #144 on: 12 November 2020, 08:32:42 pm »
Well I finally got around to finishing the tacho and it works.  It took a bit of hacking. I'm sure there's an easier way to get a low-cost working tacho for a single cylinder engine so if you know one please do share.

Here's what I did:
I bought a cheap "universal" tacho from eBay - no documentation and the cables were +12V (black) Ground (green) Signal (yellow), plus others for the backlight.
This takes a signal from the low voltage side of the ignition which helpfully is also the feed for the GX200 kill switch.
When I hooked it up, the tacho worked but because its designed to read up to 13,000 rpm I wanted to change the full-sweep range to 4500 rpm.
The circuit is based on a BAK225 chip.  I couldn't find any documentation for the chip so it "just" took a bit of experimentation to find the right resistor values to get it about right.  You don't have to change the variable resistor, but mine broke when I was adjusting it
I've got an optical handheld tacho but it doesn't give a very reliable reading so I've calibrated the new tacho as best I can.
The dial face is waterproof sticky back vinyl for inkjet printers stuck to aluminium and the needle is a clock makers part also from eBay.
 
I hope it doesn't shake to bits when I fit it to the cyclekart.

« Last Edit: 13 November 2020, 09:06:08 am by StefanN »

synthpunk

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Re: Bugatti Type 37 Build
« Reply #145 on: 12 November 2020, 09:19:38 pm »
From my reading of that schematic it would appear that youve set the minimum series resistance of those 2 resistors that you modified so that it is almost the same as the maximum series resistance possible with the previous two values, which were calibrated for 13000rpm fsd. Presumably therefore the lower the resistance in that series network, the higher the rpm scale readable. So if our engines top out at 3500 to 4000 ish, it would stand to reason that your values are pretty good.

synthpunk

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Re: Bugatti Type 37 Build
« Reply #146 on: 12 November 2020, 10:02:57 pm »
Im wondering if changing the reset cap from 104 to 224 might also cut the revs full scale deflection in half, due too slower integration time, without changing the resistors. Or just solder another 104 cap in parallel with the original one.

StefanN

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Re: Bugatti Type 37 Build
« Reply #147 on: 13 November 2020, 12:16:31 am »
Yes I think the resistors are the discharge path.   Frustrating I couldn’t find a data sheet even from places selling the integrated circuit.   I tried making a test rig using an Arduino to trigger a 12v pulse at 1000rpm and then 3000rpm to make it easier to calibrate, but the needle didn’t budge.   

StefanN

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Re: Bugatti Type 37 Build - gear shift
« Reply #148 on: 24 February 2021, 12:19:33 pm »
 Bit of milling, a bit of welding, some knife handle making YouTubes and the Bugatti has a gear shift lever.   Not sure what it’s going to shift, but should make for a nice bit of bling.
« Last Edit: 24 February 2021, 12:22:45 pm by StefanN »

Applejack

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Re: Bugatti Type 37 Build
« Reply #149 on: 24 February 2021, 01:39:17 pm »
Nice work Stefan should look great on the car 👍.