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LongRat

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About LongRat

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    http://www.fulloption.co.uk
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  • Location
    Wotton-under-Edge, UK
  • Interests
    CNC machining, model engineering, scratch builds, model engine building, RC car racing, model flying.

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  1. Once you have the moulds set up, the actual production time for a plastic sprue of parts is very low. You can get thousands of parts per hour (have a look at Lego factories). That makes plastic parts cheap. The RC hop ups you are talking about are almost always machined, that's a comparatively slow and expensive process. Plus, it requires multiple post-processes such as deburring, surface finishing, cleaning, anodising and some of those are almost as slow as the machining step. Whilst the volume of material is also more costly than plastic, it's the time they take to produce that drives the cost mainly.
  2. I share this sentiment. A key point for me is that what we consider 'normal' use of these cells in RC models is probably considered to be abuse by the cell manufacturers. I believe this is a key reason not a single RC LiPo battery has the cell manufacturer named on the packaging.
  3. Capacity can be the same with both batteries and the lipo can put out more power and for the same or even longer time. There is more stored energy in every mAh of capacity in a lipo battery than in the same mAh in a NiMh, because the voltage during discharge is higher.
  4. More current doesn't mean more power. More current at a given voltage, yes. In the NiMh case, because of the greater internal resistance of these packs, you need to pull more amps to get the same power because of the greater voltage sag. A 30 amp discharge on a LiPo might give you 210 Watts (30A x 7V). A 30 Amp discharge on a NiMh might give you 180 Watts (30A x 6V)
  5. Capacity is not energy. So a 5000 NiMh will have less stored energy than a 5000 LiPo. This is the main reason the LiPo will still outlast the NiMh on the same load. Amp-hours (capacity) represents the total stored electric charge. Watt-hours represents the total stored energy. You need to consider the voltage at all points along the current discharge curve to measure total energy discharged.
  6. The difference between RC batteries and all other consumer lithium batteries, including phones, laptops, scooters and everything else, is that RC batteries have no in-built protection circuit. The protection comes from the users correctly setting the charger up. On top of that, the current spikes and general mechanical abuse that the batteries endure are more severe in RC than any other application I can think of. These two reasons are why battery fires are orders of magnitude more common in RC than in other applications. Using the fact that thousands of tablets are charged daily in kids bedrooms to imply RC LiPos are perfectly safe is like saying top fuel dragsters are safe because you've never had a 300mph blowover in your commuter SUV. RC LiPos are more dangerous than other batteries, but are safe enough for many peoples' tastes, including my own. But if anyone doesn't feel comfortable using them, I can fully understand that too.
  7. Very much mission accomplished. Really like the look of your Pumpkin, top work.
  8. The buzz for me as an adult is not just the ability to now buy those things, but much more, the acquisition of skills to do my own thing to a level I dreamt of as a child. That's the value of age and experience. The RC hobby for me is a continuing challenge to improve my own ability to think up and make what fires my imagination. That's mainly why I don't spend a lot of money on RC cars, but more so into tools, workshop and materials. I remember when I saw a model 1/8 scale Napier Deltic engine at a show nearly 20 years ago now. An utterly sensational build by a guy who was old, but had kept up the pace of learning and hadn't stagnated. The same feeling came over me as when I used to dream about driving an Avante. I knew I couldn't build anything like that Deltic engine then. Now, I know what all the steps would be, and if with the right motivation I think I could get close. It's the combination of satisfaction of improving yourself, and admiration of those who are several steps ahead, that gives the hobby real meaning to me. I have memories of seeing a friend's Grasshopper and thinking how cool it was. So much faster than my Nikko Turbo Panther. Now, to get the same feeling as then, the Grasshopper needs to perform in the way I recall in my childhood perception (not how it actually did). The challenge of getting my cars to those levels is what I enjoy.
  9. Just compare the total stored energy in Watt-hours. 2S 5000 mAh -> 7.4V x 5Ah = 37Wh. 3S 2000mAh -> 11.1 x 2Ah = 22.2Wh. Do with that energy what you will, by specifying the motor/ESC/gearing to draw the power of choice. Either run longer or run faster. Differences in discharge rates probably make little difference. If the higher voltage battery has a lower C rating, that's not really a problem because it doesn't need to discharge such high current to develop the same power. So this balances out.
  10. Took this car to the Revival meeting at Broxstowe RC club. Had a bit of a practise on the track, although couldn't race it as it's obviously not genuinely a Grasshopper, or vintage. I found that it could do with more rear traction, those truck tyres are a bit too hard really. Also, bent a suspension arm so a new version will be coming soon. Traction issues solved using Kyosho Scorpion tyres on my own wheels. I think this is the sweet spot, with the right look and awesome grip. I'm using Kyosho's SCW023 hard inserts.
  11. A few things to consider. RC LiPos, unlike those used everywhere else, have no internal failsafe circuitry within the battery. Comparing them to phone and laptop batteries is unrealistic. RC LiPos are not matched to a particular charger and so are charged only via the expertise of the user, and are thus exposed to any errors the user may make. RC LiPos have been known to burn even when treated 'correctly'. Bear in mind the electrical stress placed on the battery by RC is known to exceed what cell manufacturers rate them for - ever wondered why not a single RC LiPo has the cell manufacturer's name on the case or packaging? One particular thing I take issue with is overblown C rating. You won't catch Panasonic rating a cell at 100C for example, but you will see that nonsense plastered all over many RC batteries. If RC LiPo fires were only as rare as plane crashes, every plane in every country would have been grounded for years. These batteries are not without risk. I use them, but I understand why people wouldn't want to. I won't let my kids handle them until they are 10+ years old, at least.
  12. Le Mans 480T is 26x1 wound with 0.75mm diameter wire, has ball bearings and adjustable timing. And it's a very good looker.
  13. Bit of beachside action, managed to bend part of the rear hub hitting a beach hut... upgrade coming soon on that. Wasn't a great design anyway.
  14. Video of the original version from a while ago. I'll get some decent video hopefully once the project is complete.
  15. Detail of the new rear wheel. The centre section is grit blasted for a bit of contrast.
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