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  #61  
Old 04-02-2014
cunawarit cunawarit is offline
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Impressive I said it before, but I love this idea. Cannot wait for you to report back on how it performs.
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  #62  
Old 04-02-2014
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SLEENAD SLEENAD is offline
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Nice work on the front aswell!
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  #63  
Old 05-02-2014
morpheus2010 morpheus2010 is offline
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Thumbs up Nice engineering

Cracking piece of kit Assume you have access to CNC facilities with the front end you have built

Looking forward to your on track report
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  #64  
Old 05-02-2014
mr. ed mr. ed is offline
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Nice work indeed!
A small questions: why did you put the battery in front of the electronics: is it lighter?

And a small idea: the milled logo on the chassis bottom looks nice but a smooth bottom would be better for performance, nit? Maybe you could coulour some resin and have the logo stand out stronger whille keeping the bottom flat.
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  #65  
Old 05-02-2014
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Thanks for the comments guys.
To answer the questions - I have built up a nice workshop at home over the years, including a home made CNC vertical mill with which most of this car was made. There are only a couple of parts left which are original Mardave.
As for the flat floor, while in theory smooth would be better, it really won't make much of a difference I don't think. The reality is that the flow of air under this chassis will be heavily disrupted already at the centre chassis point by what's upstream - junction between alu bumper and carbon chassis, foam bumper lower edge and body shell. Plus there's that huge cavernous hole where the motor is at the back.
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  #66  
Old 05-02-2014
SlowOne SlowOne is offline
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In LMP12, if you run a chassis that is flat from front to rear, the car will understeer at speed. The holes cut in 12th chassis' between the front steering blocks give the car high-speed steering. No, I don't know why either!

The other thing to bear in mind is that with a gap between chassis and ground of less than 3mm, the air becomes turbulent and the car gets spooky. Sine the car decks out at this level of ground clearance, that is a greater problem for handling so the poor air flow isn't noticed.

Many moons ago Phil Greeno made a full ground effect 12th car that actually worked quite week. Jason Deardon did it with a Pro10 car and that was awful! My approach is to do what everyone else does. Mechanically I can past muster, but aerodynamically I ran out of talent real quick!
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  #67  
Old 05-02-2014
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I built a ground effect car in 2001.





It was extremely stable at high speed. I couldn't compare it with and without the undertray though because it couldn't really be run without it.
They key is to get the centre of (minimum) pressure located in a position that is favourable to the handling you need. Too far rear and it will promote understeer, too far forward and the reverse will be true. If putting holes in the 1/12th chassis close to the front promotes high speed steering, and it IS an aerodynamic effect (big if), then this must be due to a shift in the centre of pressure under the car towards the front. But it could just be the introduction of more front flex and more mechanical grip under high loading.
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  #68  
Old 06-02-2014
mr. ed mr. ed is offline
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LOL I didn't think of the aerodynamics when suggesting smooth is better.
I'm primarily a buggy guy and was worried of the contact between the chassis and carpet.
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  #69  
Old 07-02-2014
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Quote:
Originally Posted by mr. ed View Post
LOL I didn't think of the aerodynamics when suggesting smooth is better.
I'm primarily a buggy guy and was worried of the contact between the chassis and carpet.
Haha! Hopefully it won't be an issue. I do quite like the idea of a coloured resin in-fill. Might mix up some epoxy with some paint and try that.
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  #70  
Old 07-02-2014
mr. ed mr. ed is offline
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better use some kind of pigment: like childrens waterpaint disc, or crayon. The solvent of the paint might react with the resin.

I just ordered the moter again: finally got told by hobbyking my first order failed and they'll refund me
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  #71  
Old 07-02-2014
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Post up here when you have it in your car.
Just leaving for the track. Hopefully this will run well.
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  #72  
Old 08-02-2014
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Ran at Gloucester RC club last night. Failed to finish both heats due to the diff loosening. I was hoping the diff tension screw would be sufficiently secured with thread lock, but it wasn't the case. For the final I went with a load more thread lock and the diff setting was held, the car was superb and easily won. However as I had qualified last in the bottom final that doesn't say a lot, but the times were A-final competitive. I think with a bit of tweaking it will be a top contender. Overall I am very happy with it.
I will bond in a stud and use an M3 nyloc nut I think, that should fix the diff loosening problem.
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  #73  
Old 15-02-2014
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Ran last night with bonded stud, diff held together perfectly. Ended up 5th in the A final so pretty good result. Interestingly this is using a lot more battery energy than the solid axle no-diff version. I think it is a combination of being able to put down more power (so driving with more throttle more of the time) and friction from the needle roller bearing. Need to try some dry lube on it.
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  #74  
Old 15-02-2014
morpheus2010 morpheus2010 is offline
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Good to hear it's competitive. A sprinkling of magic dust could help ( Graphite powder )
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  #75  
Old 15-02-2014
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Yeah I have some somewhere, got to dig it out. Just can't remember where it is!
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  #76  
Old 18-02-2014
morpheus2010 morpheus2010 is offline
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Default Magic dust (Graphite powder)

Quote:
Originally Posted by LongRat View Post
Yeah I have some somewhere, got to dig it out. Just can't remember where it is!
Below supplier 50gram £3.56 free P&P if yer stuck for some

CPCFarnell kasp-security/k30050/microfine-graphite-powder
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  #77  
Old 24-02-2014
mr. ed mr. ed is offline
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Well, I had my first try with the 740Kv moter, and probably should have gone for the 1100Kv instead

I used the original yokomo YR-4 tourer and removed the entire front transmission and the center shaft with its spur and pulley. tapped the shaft of the moter through to the other side and mounted a 5mm bore pulley on the shaft. A shorter belt over the pulley to the diff was all it needed to finish the conversion. But I took some extra time and rearranged the electronics and switched to saddle packs. Al that to bring the weight more centered and further to he back: all possible now the fwd belt and spur were out of the way.


Unfortunately I only ever found one of those pulleys I now use as 'pinion' and it is clear it needs more teeth. The acceleration to top speed is immediate but it goes noticeably slower at top speed than a 540 mabuchi powered TT-01. It also comes to a stop way too quick instead of rolling out.
(No, the belt tension is fine, thrust me on that)

I guess I could try finding another pulley before upping the moter: anybody with ideas? It should be M3 module and a 5mm bore.

I do still have other ideas for use of the 740 KV moter, so It's not hat bad if I can't get the YR4 to work as it should. (The car was running great before, and 4WD, so I don't mind getting it back to its 'normal' state)
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  #78  
Old 24-02-2014
morpheus2010 morpheus2010 is offline
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Thumbs up Another IMA

Any chance of Pic's Mr Ed?
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  #79  
Old 24-02-2014
mr. ed mr. ed is offline
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I 've just posted some pics in a new thread in the 'I made this' section:
http://www.oople.com/forums/showthre...618#post840618
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  #80  
Old 25-02-2014
fathead fathead is offline
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Longrat,
A possible alternative to that quite large (and I assume relatively heavy) roller bearing on the motor would be to use 3 or 4 small ball bearings spread evenly around the motor with small holders, could be a bit lighter and less rotating mass maybe.
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