Jrkline "Wheel Whisperer" Posted March 10, 2017 Share Posted March 10, 2017 19 hours ago, Chriull said: Wow - the third photo seems to be the perfect example for how _not_ to mount a mosfet on a heatsink... a nice spacing between the mosfet and the metal and a huge blob of paste inbetween - or are my eyes deceiving me? The adhesive is to dampen and resist vibration.The heat is primarily dissapated through the metal in the attachment screw. Link to comment Share on other sites More sharing options...
esaj Posted March 10, 2017 Share Posted March 10, 2017 31 minutes ago, jrkline said: The adhesive is to dampen and resist vibration.The heat is primarily dissapated through the metal in the attachment screw. What? That doesn't sound right, AFAIK the "adhesive" is thermal paste, meant to fill in small cavities that are even in the most shiniest and smoothest looking (with naked eye) surface, so no air is left in-between (that would act as a thermal insulator). TO-220/247 and similar casings typically have a metal backplate that dissipates most of the heat, here's a modelling of a typical TO-247: In some cases, the attachment screw-hole can actually be isolated (electronically, and thermally) from the backplate, as the backplate is usually also directly connected to one of the legs, typically (if not always) the middle leg: But, that makes me wonder what they've used to insulate the backplate electrically from the heatsink..? If the middle-leg is connected to the backplate, and all the mosfets are connected to same heatsink, it would cause a short-circuit to occur (either between phases and/or shoot-through). Anyone know the GT16 mosfet-spec? Edit: Lizardmech had dug up the info, here's the datasheet: http://www.infineon.com/dgdl/irfp4110pbf.pdf?fileId=5546d462533600a4015356290ec51ffe IRFP4110 in TO-247 package Not exactly modern or very high-performance today, guess it comes down to price & availability Not to say it's bad either (and many older wheels use much weaker mosfets, in TO-220 -casings), there are lower Rds(on) -models available, but they're usually much more expensive (3x the price per unit for example) and come with some tradeoffs (higher gate charge for example) for the same voltage. Link to comment Share on other sites More sharing options...
Marty Backe Posted March 10, 2017 Share Posted March 10, 2017 1 hour ago, jrkline said: The adhesive is to dampen and resist vibration.The heat is primarily dissapated through the metal in the attachment screw. Back when I did hardware (maybe things have changed in the intervening 30 years) we placed thermal grease between the device and the heatsink to assure the transfer of heat away from the device. It had nothing to do with vibration. Link to comment Share on other sites More sharing options...
Carlos E Rodriguez Posted March 24, 2017 Share Posted March 24, 2017 Does ROCK Wheel have a website? I saw some videos of the GT16 flying on the streets. It looks like it goes fast! The Controller board does not look like a GW one. And the MOS look huge compared to GW. I saw a spec of 180 AMPS in aliexpress web page describing the GT16 Link to comment Share on other sites More sharing options...
esaj Posted March 24, 2017 Share Posted March 24, 2017 39 minutes ago, Carlos E Rodriguez said: Does ROCK Wheel have a website? I saw some videos of the GT16 flying on the streets. It looks like it goes fast! The Controller board does not look like a GW one. And the MOS look huge compared to GW. I saw a spec of 180 AMPS in aliexpress web page describing the GT16 I don't know if Rockwheel has a website, but the mosfets seem to be IRFP4110's, which is pretty much the same as IRFB4110 used for example Gotway ACM (whatever the newer version is), as seen in @Rehab1's autopsy pictures, except the "P"-model uses a TO-247 -case, which is larger, and thus helps with cooling (larger surface-area touching the heatsink, datasheet figures suggest that the case-to-sink -thermal resistance is roughly halved). There's a bunch of posts about the GT16 in the Rockwheel -subforum: http://forum.electricunicycle.org/forum/33-rockwheel/ The datasheet for the mosfets are here: IRFB4110: http://www.infineon.com/dgdl/irfb4110pbf.pdf?fileId=5546d462533600a401535615a9571e0b IRFP4110: http://www.infineon.com/dgdl/irfp4110pbf.pdf?fileId=5546d462533600a4015356290ec51ffe As for the 180A -spec (and mosfet specs in general), I have a very unfinished long post in a text-file, that talks about the datasheet-values and how much they lie Or more like, how many other factors you really need to take into account, and then realize that you can't get even near the theoretical absolute maximum values in practice... Don't know if I'll ever finish and post it, but I think this quote (from http://electronics.stackexchange.com/a/216944/128374 ) pretty much sums it up: Yup, that's the way MOSFET datasheets work. The maximum current rating really means "This is the maximum current you can ever possibly get thru this thing, if you were to somehow not violate other specs in the process, although we have no idea how to do that. We put this here because we think it's cool, and maybe someone is dumb enough to buy a truckload of them before realizing they can't actually run the part at this value for any set of real world conditions". Basically, each of the limits of the device are specified separately. You have to look at what you're doing and carefully check each one. The real limit on current is usually die temperature. To check that, look at the max Rdson for your gate drive level, compute the dissipation due to your current, multiply that by the die to ambient thermal resistance, add that to your ambient temperature, and compare the result to the maximum die operating temperature. When you figure all this backwards to find the maximum current the device can take before overheating, you'll usually find that's well below the absolute maximum current spec. Link to comment Share on other sites More sharing options...
houseofjob Posted March 24, 2017 Share Posted March 24, 2017 1 hour ago, Carlos E Rodriguez said: Does ROCK Wheel have a website? Yes they do, but not an English one: Rockwheel Korea Rockwheel China Neither have really been updated in forever though. Link to comment Share on other sites More sharing options...
Carlos E Rodriguez Posted April 20, 2017 Share Posted April 20, 2017 Can someone update a comparison of the ACM 84v with the GT16 84v? Link to comment Share on other sites More sharing options...
cbgti Posted September 2, 2017 Share Posted September 2, 2017 Gotway wheels are very smooth and I love the "Leisure Mode"... Unbeatable! I don't know if the "Soft" mode could be the same on the RockWheel GT16. Link to comment Share on other sites More sharing options...
Marty Backe Posted September 2, 2017 Share Posted September 2, 2017 On 4/20/2017 at 9:31 AM, Carlos E Rodriguez said: Can someone update a comparison of the ACM 84v with the GT16 84v? I've ridden both wheels, although only about 7 miles on the GT16. The GT16 is a much lighter wheel and therefore feels less stable (fun) at very high speeds compared to the ACM, which is a fat little piggy that hugs the roads even at 25mph. The GT16 shines in that it's very fast and extremely nibble. It's ride mode is also extremely hard (Ninebot hard) so I really enjoyed riding backwards, etc. If you want a 'fun' wheel, go for the GT16. If you want more of a road machine, go for the ACM. And of course if you want to enjoy long (40+ mile) rides, go with the ACM. Link to comment Share on other sites More sharing options...
Mrd777 Posted September 3, 2017 Share Posted September 3, 2017 16 hours ago, Marty Backe said: I've ridden both wheels, although only about 7 miles on the GT16. The GT16 is a much lighter wheel and therefore feels less stable (fun) at very high speeds compared to the ACM, which is a fat little piggy that hugs the roads even at 25mph. The GT16 shines in that it's very fast and extremely nibble. It's ride mode is also extremely hard (Ninebot hard) so I really enjoyed riding backwards, etc. If you want a 'fun' wheel, go for the GT16. If you want more of a road machine, go for the ACM. And of course if you want to enjoy long (40+ mile) rides, go with the ACM. Marty is absolutely correct here. I own both wheels and use the GT16 more in NYC, It seems like a perfect machine for the city. The ACM is much more planted to the ground at speed. I just did a 34 mile ride on gravel keeping speeds between 17 and 22 mph, and the ACM performed beautifully. I still had 38% battery left... The GT16 feels a bit insecure for me at 21mph. Mark Link to comment Share on other sites More sharing options...
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