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Sep 16, 2019, 03:05 PM
Jetdrives R Us
sundogz's Avatar
Thread OP
Mini-HowTo

Proboat RiverJet to 35mm FJD conversion


Now that the 35mm FJD is available as a drop-in conversion (post 236) for the dainty pump in the PBRJ I thought it would be good to start a thread so we could share experiences, tips and any problems with the conversion.

Since I have a Hull and decal set I obtained for the ride plate project(post 235) I've decided to outfit it with the 3D printable drive. I already had a steel rod (spoke) type grate printed from the earlier project (.stl files included in the pump Zip file) so was ready to install the pump.
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Sep 16, 2019, 03:11 PM
Jetdrives R Us
sundogz's Avatar
Thread OP
3D printed holes sometimes turn out rough, so I started by drilling out the holes to size = grate holes 2mm, stator holes 2-1/2mm

I highly recommend and usually install all jet drives by epoxying them in place for strength/ less leaks/ worries. I use West systems 2-part epoxies as they stick best and are non-brittle when cured. But I have been asked if I would install this one so it could be removed if needed. So I've decided to use a butyl rubber caulking tape in this build. You can roll it into a noodle and it adheres well so was an easy choice to make.

Or so I thought. Turns out it is not very easy to compress and I had to resort to clamping it in - in order to get the screw holes to line up.
I had planned on where/how much caulk tape to use and had to disassemble it thrice to add more to stop leaks. You can't overdo it. When done I put some all around the circumference of the pump as insurance.
Sep 16, 2019, 10:46 PM
Just Plane Nutts
AirDOGGe's Avatar
35mm in the PRJ, what Proboat should have done originally with it, assuming the hull can handle with that much power (it should).

I like this mod. Should come with stickers you place near the throttle on your radio..... position markers labeled "REVERSE", "NEUTRAL" and "BAT-OUT-OF-HELL".


Gonna give Mr. Musk's Falcon rockets some competition there.
Last edited by AirDOGGe; Sep 16, 2019 at 10:53 PM.
Sep 17, 2019, 12:34 AM
Jetdrives R Us
sundogz's Avatar
Thread OP
It did come with a 35mm pump, albeit a fragile one that is difficult to service. This change may not make it faster but it will be more durable, easy to service, and parts will be easily modified and inexpensive to make. Whatever happened to Ralph? This might give him reason for concern....
Sep 17, 2019, 09:26 PM
Jetdrives R Us
sundogz's Avatar
Thread OP
The countersunk hex flat head grate screws strip out easily. I dipped each screw into lubricant (I used teflon spray in a cup) before installing to make cutting threads in the plastic easier. I highly recommend changing over to torx type screws (see pic). If you're using torx screws, there's no need for lubricant. Don't over-tighten.

You can remove the caulking from screw holes by just twisting a drill bit by hand. I found that when using caulking to install the pump the stator holes are very tight to start. I resorted to enlarging the holes a bit to make life easier.
Sep 18, 2019, 12:15 AM
Just Plane Nutts
AirDOGGe's Avatar
Quote:
Originally Posted by sundogz
It did come with a 35mm pump, albeit a fragile one that is difficult to service. This change may not make it faster but it will be more durable, easy to service, and parts will be easily modified and inexpensive to make...

Gotcha. Thought it came with a 29'er.
Sep 21, 2019, 03:56 PM
Jetdrives R Us
sundogz's Avatar
Thread OP
I am using the zero backwash nozzle and reverse bucket (post 1292) on this boat. You have to scale the .stl from 45mm to 35mm to fit. I scaled it to .78 and had to grind a little from inside the collar to line up the screw holes. I suppose .79 would have been better, but I had already printed the bucket and nozzle and am too frugal, I suppose. After assembly you epoxy it onto the stator.
Last edited by sundogz; Sep 21, 2019 at 04:48 PM.
Sep 21, 2019, 04:21 PM
Jetdrives R Us
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Thread OP
I'm just going to re-post this next info that I had previously posted on MiteyF's Bermy thread. It is pertinent to the next step of installing the impeller/shaft/stator:

Install a 3mm ring of sealant around the stator wear ring where it meets the flange. I prefer butyl rubber calking for this. Install the shaft/impeller into the stator bearing. The impeller should not touch the stator fins when pushed back and turned. If it does, put a spacer behind the bearing to prevent this.

With motor and coupler in place (all screws loose, washers on the motor mount screws) slide the stator/impeller/shaft into the inlet housing through the seal and guide it into the coupler. Install and tighten the 6 stator fastener screws.

Centering the coupler between the motor and pump shafts (motor held against mount), tighten the coupler grub screw onto the flat of the impeller shaft. Now (holding the motor tightly against the mount) tighten the coupler grub screw on the flat of the motor shaft. Finally, tighten the motor screws.

Using this method puts a bit of preload onto the motor and when things settle in eliminates excessive play in the driveline. The coupler will be off center slightly due to shaft bore clearance but it won't cause detectable vibration unless the clearance was excessive or the coupler was poorly made.
Last edited by sundogz; Sep 21, 2019 at 04:50 PM.
Sep 21, 2019, 04:46 PM
Jetdrives R Us
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Thread OP
I'll be using the motor and watercooled mount from a previous project - Proboat Recoil 26. It is part number DYNM3951 as opposed to the DYMN3952 that comes with the Riverjet. It should do the job, but I can't find the watts (power) listed anywhere. I guess it's a secret.

I made a servo tray to attach two mini servos to the top of the pump. I'll be using Emax ES08MAII's for the steering and the reverse bucket. This is an experiment - these are surprisingly torquey all-metal geared mini's at 2kg (6v) and should do the trick while keeping the (high suspended - on top of the pump) weight down. We'll see. I've posted the .stl file if you want to try it.
Sep 27, 2019, 04:45 AM
Jetdrives R Us
sundogz's Avatar
Thread OP
The servo tray wasn't secure enough with just the cable tie holding it all in place, so I epoxied it to the pump. That worked nicely, and with double backed tape under the servos the cable tie retains the servos securely. After some judicious bending of the servo rods there is no 'servo squirming' or buzzing at all. Edit: I was going to make a movie of the 'silent servos' and the reverse bucket servo is now faintly buzzing. I'll leave it alone. I spent a lot of time bending those rods so the servos weren't under any strain. As it turns out, I was able to use the original servo rod holes in the hull, so I have included a stator with notches (post 236) with the original .stl files that you can use as a template to drill the inlet housing.

My parts supply was limited as far as rod clevises/ends but I had a bunch of collars, so I just bent the ends of the rods to fit. This method functions nicely, but may not look as sleek as other methods. It also doesn't allow KiwiKrawlers' method of using tubing to go through the hull. But by enlarging the holes I was able CA glue common boots in place since they won't need to be removed for servicing as with the original pump. And the bends in the rods are no problem for insertion through the boots.

I had in the past recommended full size servos for steering but many times had read that members used mini's with no problems. And I see why - these Emax's have gobs of torque. And with metal gears should hold up nicely. The lower weight helps in my application and the smaller size would help out with the limited space in smaller boats. We'll have to see how they do on the water.

I relocated the cooling water outlet tubing to the transom top, and ended up drilling holes in the bucket arm for the servo rod so I could use the original hole in the hull. I will fix the bucket .stl file(s) to reflect this change since it is better that the original concept. I decided to use a Mystery 200A boat speedo that I had in stock and packed the ends with ShoeGoo to waterproof it. The ESC had 8mm bullet connectors which I left intact - so made some adapters for the motor and XT60 battery connects. A bit much is better than not enough in this case, and I can easily repurpose the speed control by just removing the adapters. If I were to do it over, I would put the ESC on the starboard side. I can fit a wider battery in the original tray.
Last edited by sundogz; Sep 27, 2019 at 10:17 AM. Reason: servo chatter
Sep 29, 2019, 02:07 AM
Registered User
KiwiKrawler's Avatar
Following this build with great interest. Largely due to the fact I have recently received a parcel with the same 3D printed jet drive for the River jet. Firstly I want to thank Sundogz wholeheartedly for the kind gesture of supplying me with the drive for my conversion. Itís humbling that although we are on the other sides of the planet...a passion for these miniature drives transcends the distance and I am fortunate enough to be helped out by another enthusiast in our chosen hobby. Sundogz....your a legend mate. Thanks.

Secondly...Iím sure our builds and installations will differ in many ways. So it will be interesting to share both builds here. If you donít mind me posting on your build thread of coarse Dave. Just say if youíd prefer I donít.

Just thought Iíd whack up a couple of picks of this awesome drive. Personally itís my first FJD Iíve had my hands on...as Iím a complete novice in the 3D printing arena. But now Iím wondering why Iíve been faffing around for so long with all my other drives. Cos this thing ticks all the boxes and some. Particularly like the fact the impeller and wear ring is in the stator. So if you ever have a mishap maybe smashing an impeller blade...or ingesting some gravel causing damage. Itís just a case of replacing the stator/nozzle. And the drive body is still mint and totally unscathed. The Mickie Beez drive is the only one I have with a totally separate wear ring in the stator. But this drive is similar in the fact the drive body will remain undamaged...no matter what happens to the impeller and stator out back. Nice!
Sep 29, 2019, 03:05 AM
Jetdrives R Us
sundogz's Avatar
Thread OP
Thx for the kind words Kiwi, glad you got the parts OK. And of course I don't mind you posting here, that's what this thread is for By sharing different ideas we're bound to find the best ways and means of converting this boat to something a bit more durable and fun to operate.
Looking forward to seeing your build come along. I'm hoping to get mine on the water soon.
Sep 29, 2019, 05:21 AM
Registered User
KiwiKrawler's Avatar
Cool man thatís what I was hoping to hear.

Have been working on the jet drives installation today. As I want a nice water tight seal between drive and hull...I have spent a bit of time smoothing out the base of the jet drive before installation. With the hundreds of striations as a result of the printing process...I spent a good hour sanding the underside of the drive with wet & dry sandpaper on a piece of glass to result in a nice flat surface to marry up to the base of the hull.
Sep 29, 2019, 05:45 AM
Registered User
KiwiKrawler's Avatar
I then spent some time on the stator. I decided to go out on a different tangent...primarily to show that there are always more than one way to skin a cat. Or in this case...modify a jet boat. Iím installing a different zero backwash arrangement to my stator. Sundogz has showed his one epoxied to the stator...which allows the fitment of the cool reverse bucket. But I have a bit of an addiction to speed. So for now will leave off the reverse bucket as it will invariably get destroyed in a high speed tumble. I want to drag race a stock River Jet with the 3D printed FJD version to see how each performs. I have both...so it will be a side by side drag race. Should be fun. But for now the backwash arrangement Iím running is off another popular drive readily available. And with a bit of work with a rat tail file it fitted like it was designed to be on there...
Sep 29, 2019, 08:50 AM
Jetdrives R Us
sundogz's Avatar
Thread OP
My thoughts on the 3D striations are that they give the epoxy something more to hold onto. We usually have to sand a smooth surface so the epoxy will adhere better. But I don't think your sanding will hurt anything.

The Zero backwash/reverse bucket Zip file (p. 1292) includes a version of the collar without the reverse bucket bosses in case you just want the nozzle. But yours is interesting - is it rigid or like rubber?


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