Early May 2018, Mark was selling his jet units at 230 GBP per piece. It seems difficult to get them.
2 x (motor £45 + ESC £80 + 53mm carbon fibre composite jet unit at £230) = 2 x 355£ = 710 £ / 800 €.
Read that MHZ recommend two units of their 52mm on a jetboard.
Mark shops from HobbyKing. His first motor (now discontinued) was a 1600kv motor 70A.
Latest tests have been performed on 500 to 530KV 12s motor on 6s = 11.000 rpm and managed 22 to 29kmph. Target rpm is 17krpm. On Hobbyking, the power of those motors is twice that one of first motor that is 3 to 4 kw.
Seems that the propulsive power is now 7-8Kkw for a top speed of 30kph.
ESC ?
80£ = 100USD, Mark’s ESC is very likely this one, black cover with Turnigy written on it:
Recommended ESC with first motor is 70A. Mark has oversized his ESC by a 2.5 factor with this Turnigy Marine 180A BEC Waterproof Speed Controller with Water Cooling
With inner surface covered with a few layers of carbon because there is also the issue of sand and debris striking the inner part of the tube. That’s why MHZ, Graupner make them in cast aluminium.
If there wasn’t this wear issue, another candidate with nice surface finish could be a 50mm rain pipe heated in hot water and curved.
Then there is the impeller sourcing. It must be very rigid for optimum efficiency that 3D printing does not always offer according to @VeFoil . The 49mm Graupner in a 50mm inner diameter of a rain pipe would be a winner. I’m not sure Graupner sell them as spare parts.
if he is using motor given for 3-4kw on 12s , with 6s, he is pulling more 1.5-2kw on each , plug wiring … above 120A get hot! i don’t think this esc can take +100A for a long time
You guys have your mph and kmh mixed up the 27 is miles per hour that run was actually 43.5 Kmh or 27 mph. Mark ended up using a rocket 730 kv motor and a flier 240 amp esc good to 12s or possibly 16s .
I was the first person he sold the jets to in the US. I was a bit of a beta tester ( unknown to myself) so I told mark every issue I was having and he promptly made a video explaining how to avoid that issue.
I spent a full year building a jetBoard using tow of his jet pumps. They are very powerful but in their current form flawed in that the impeller shaft and it’s thrust bearings spin inside a tunnel made of black epoxy this set up works great as long as nothing heats up too much. If the shaft generates heat it transfers it to the bearing race which begins to melt the epoxy once that happens the whole set up is out of round and causes other failures. One of my jets must have had this happen very early on and no matter how perfectly aligned I got the motor and jet pump as soon as I put a load on the board one drive would fail. Either a coupler would twist, overheat and fail or the impeller broke away from the shaft but it never ran properly with two jets . Now mark is a light guy probably 140 lbs soaking wet where I’m 225 and I was running my set up with big batteries and lots of them and the board was an 11’ paddleboard cut down to 10’ so a lot more weight and drag compared to marks little 7 ft board and 4 minute run time batteries. So his jets do work just not for us bug guys. I have yet to hear him say this so be careful if you buy the jets they will work is perfectly aligned and the rider is 150/160 lbs max. That’s been my experience. The whole time I was trying to get marks jets to work and failing my single drive MHZ Jet 52 was running like a Honda Accord and one jet on an 11 ft paddleboard had a top speed of 9 mph or 15kmh so two of em will get me all the speed I want and they are cast alloy with no plastic parts so none of the issues I experienced with marks jets .
I have been building my own packs from some foil packs I got from batteryhookup. So I’m building 5s packs and running 2 in series to 10s packs with leopard 5692 530kv motors . That gives me a theoretical max rpm of about 21,000 rpm or 19,000 since there is a 10% loss of efficiency it’s a little high and the leopard motors are only rated for 88 amps continuous which is a bit low I also have SSS 56104 420 kv motors which on 10 s gets me to the 16,000 rpm sweet spot if MHZ’s spec sheet is to be believed.
Hmm, i was building a jetboard with 3d printed parts from pla, but i was thinking to cast them from aluminum , at least some essential parts. Will think about it …
Did another test today, after moving the esc 20 inches away from motor, used 10 gauge for the phase wire extension that stayed nice and cool but the stock motor wires thin 12 14 gauge were 150deg in 10 minutes. To hot for me, might move the motor up shorten board another foot
Decided to move esc’s back to the motor jet box and add a foot or so more 8ga battery wire and test again. It’s a big board I’m trying to decide how far forward to put the batteries
