After a successful two hour dive following Marcus around Vobster whilst he photographed the walls around the 22 m area the afternoons dive didn’t go so smoothly. Feeling a bit scootered out after the mornings dive we jumped back in anyway and whizzed around this time unencumbered by camera equipment . Nearing the end of the dive my scooter started to make strange noises, the normal Aquazepp racket had taken a turn for the worse and didn’t sound healthy at all so I swam it the short distance back to the entrance point, pondering what might be causing it. I initially suspected that the motor might have come loose on its mounts and the gears might not have been meshing optimally.
Once back at home I had a look in the tail cone but found the motor still firmly bolted into place, instead I could see that the large drive gears teeth had partially stripped. No prop jams or other issues had been encountered on the dives so why this happened is a bit of a mystery, old age perhaps ? The drive gear attached to the motor shaft was fine, this is only a few years old.
Lower portion of teeth stripped
This happened in February 2022 and writing this is June I still haven’t bought a replacement part, I have been busy with other things and the scooter doesn’t get much use over the summer when the caves are a better proposition for diving than Vobster. I think I might take this as an excuse to rid the scooter of the noisy drive train and go with a direct drive motor, at the moment replacement motors for the CUDA are on sale and are suitable for direct driving a scooter.
https://dive-xtras.com/products/cuda-motor
It seems recently that someone has taken over ownership of what was left of the Aquazepp brand, more information can be found in this video below:
Estimated track overlaid with scaled image from Google Earth
Having created a dive proof device that can accurately measure and record magnetic bearing, depth and other useful information like temperature, pitch and roll I was keen to see how it might perform as used to plot the route covered underwater by a diver. It was still without distance measurement capability at this point but assuming a fixed speed is maintained then this isn’t an issue, so I chose to strap it to the front of my Aquazepp and do a test to see if this idea was worth further pursuit with the hardware I have.
A device like this has been created before and carries the nickname of the ‘Lazy Boy Mapper’ developed by John Volanthen around 10 years ago and was used to great effect in long and deep caves where normal survey is not practical . Commercially available devices are also available by the like of Seacraft though these stretch into the £1300 region.
Around Christmas 2020 we were emerging from tier 3 lock down but yet to be dropped into tier 4 so a flurry of quarry diving activity took place due to the weather and ban on entering Wales for fun purposes.
I reprogrammed the device to record data continuously which differs to how it was setup to work when used to record lines used for cave diving. Still lacking a form of distance measurement this was intended as a test to see how it would perform and if this idea was worth further pursuit, scootering was done continuously and in one speed so that a fixed estimate of speed could be applied later on.
A rather chilly two laps of Cromhall Quarry were done (in a semi drysuit) at maximum speed. The data is quite encouraging for a first attempt.
Cromhall Quarry Track
The dive begun with a lap around the perimeter before looping through the container and maintaining a fixed bearing across the middle section at a deeper depth, this was followed back on reciprocal where another loop through the same container was done, a reverse lap around the perimeter was completed before finishing with another loop through the same container before exiting.
The ability to scoot through a fixed object like a container provides a reference point to where the data should match up, without this it is difficult to know where you have covered the same ground which allows an assessment of accuracy to be made.
In the image below it can be seen that the start and the end of the dive don’t agree location wise even though i did start and finish the dive in the same place, the rest however appears to have worked very well ! A fixed speed of 60 meters per minute was applied. Speed through the water will vary slightly with subtle changes in diver position throughout the dive so differences are to be expected.
Detail view of loops through container
The magnetometer quality factor which should remain fixed on a value of ‘3’ after calibration was changing throughout the dive so this might have been caused by the proximity to the batteries or motor on the scooter so this might be a cause for the drifts seen at the start and end of the dive, it seems to cope with short exposure of large metal objects like scootering through metal containers quite well (it is an intelligent sensor not just a compass so should be able to filter out temporary disturbances in magnetic field).
Future testing and improvements will involve:
Mounting the box on the nose of the scooter, as physically far as possible from the diver, motor and batteries.
A form of speed/ distance measurement will be added.
Calibrating the IMU whilst the box is mounted to the scooter in the hope that it accounts for the field of the scooter.
Align the heading of the box better with the heading of the scooter.
Sometimes its one of those days when nothing goes your way (of course you are still happy and healthy but the given goals for the day are unachievable), I set out last week with the aim of thoroughly testing the survey box underwater and having a good ride around on my scooter before the onslaught of a dry Christmas.
A short line course was laid underwater and surveyed by a friend with a Mnemo survey device (part of which is the inspiration for my own creation). I began taking foresights and backsights with my box (having added two line clips to allow hands free alignment with the line. Unfortunately on logging shot number 13 (unlucky for some) the display somehow went back to front then froze and refused to continue to work. I had planned to survey the course three times for further device assessment and comparison against the Mnemo but was unable to complete one entire loop.
Survey box line clip and count down modifications.
We were planning a dive of around 2 hrs, a bit of surveying then some scooter fun, having had to abandon my surveying after 20 minutes I decided to take my scooter for a run wanting to assess how much battery life I might have available in its top speed. Clipping off the tow cord I took off but every few seconds the motor cut out then restarted, making the already distinctive Aquazepp sound even worse. I quickly decided that it was inconvenient but didn’t seem to be doing any harm so stopped next to a known landmark then took off for a lap on the turning of a fresh minute of the dive time on my computer.
It took 20 minutes to complete a lap which is known to be about 1100 m at the depth is was taken at. Arriving back at the line course I decided that I was against any further scootering but would surface quickly, reboot the survey box then head back to the line course to complete my goals.
Surfacing went fine, kept kit on, isolated my oxygen supply, quick minute with a handy screw driver to open the power port on the survey, rebooted and re-calibrated it, all fine so closed it back up. Mask on, oxygen back on… PSSSSSSSSSSSSSSSsss the hose had popped off of my Kiss MAV 🙁
Kiss MAV thread failure
I thought it might have just come undone to start with but after a few tries it was clear the threads had gone and that was the end of the rebreather diving for the day, I had left my scooter underwater so went back in on my open circuit bailout to retrieve it.
To top the day off there was a power cut so no hot drinks or food were available 🙁
The list of annoyances goes as:
i) Frozen survey box display and Arduino after 13 shots (hopefully a random occurrence)
ii) Scooter not running smoothly (investigation ongoing)
iii) Kiss valve thread failure (its quite old and known to happen so…)
On arriving home and sorting out gear I was still able to download the 13 shots I had taken before the device froze, after the addition of the line clips I’m happy with the few foresight and backsights I was able to take, the first belay was metal as well as one in the middle so those are expected to be bad but the rest agree quite well I think, further testing to be done to confirm.
Foresight – Backsight comparisons
So taking away some positives…. I was able to complete a ‘fast lap’ on the scooter and after charging the batteries have discovered that 24 minutes of use used 2500 mAh from each battery giving about 160 minutes of burn time at top speed. The data I was able to collect with the box is encouraging and it seems to be able to record foresights and backsights to within a few degrees away from large metal objects. The Kiss valve failed on the surface not underwater. Further testing planned….
I bought an Aquazepp LT30 (short body, single speed, 12v with headlight) in the summer of 2017. Once a new battery was installed it was fully functional despite being well used and quite old. I was getting around one hours use out of the battery and measured my underwater speed at 33 m per minute, faster than swimming but not that fast for a scooter.
Standard Aquazepp LT30 attached to a back plate for transport
Though this was ‘slow’ around the same time Marcus Blatchford was scootering around Vobster Quay with a camera attached to the nose of his vehicle at similar speeds taking photos to be processed into a model (via the process of photogrammetry) so it was ideally suited to the task of accompanying him for which many a pleasant dive was had cruising through the wintry atmospheric waters of Vobster Quay.
I was already planning on upgrading my batteries to lithium based chemistry and had been searching Hobbyking for suitable packs, some 16 ah packs came up at a good price so I purchased six of theses giving me 96 ah Vs the standard 33 ah plus the benefit of a higher voltage as these were 4 s packs which give 16.8 v when full and 12 v when empty.
Lead acid Vs Lipo batteries
I was unsure if the standard 12v motor would be able to handle the extra power but installed the batteries anyway and took the scooter for a dive. A very enjoyable 90 minutes was spent whizzing back and forth to the end of Brixham Breakwater and back, and back and back…until the scooter seemed to loose power, I had assumed the packs were just flat so ended my dive very happy that my modification had improved both the speed and the duration of the scooter. Brixham breakwater is about 900 m in length and it had taken me just under 20 minutes to reach the end so a big improvement in speed over the lead acid batteries had been achieved.
The scooter was taken home and the batteries charged, and I took it for another dive at Vobster Quay expecting to cruise around faster than before, unfortunately once the scooter was in the water the propeller was making a feeble effort to turn much like it had at the end of my Brixham dive so a bit miffed I left it at the surface and went for a swim without it. Once I got home I took it apart and began to check the batteries had actually charged which they had, on opening the rear motor compartment a burnt smell was apparent and the insides were covered with a thin layer of black dust, clearly the motor had burnt out given the extra power that it was being asked to convert from electricity to rotation of the propeller.
A source of motors from the larger Aquazepp models which run on 24 v was provided by a friend and an order quickly placed. The motor was a direct replacement for the 12 v motor, it just needed the drive gear fixing to the shaft which was achieved using a small screw fixed through the motor shaft. The 24 v motor is heavier than the 12 v motor so I had to remove some of the lead ballast that was required when swapping from lead acid to lipo batteries.
Drive gear fitted to 24v motor (metal gears are why the Aquazepp has such a distinctive sound)
Confident that a motor rated to work at 24 v could handle 4s lipo packs some more test dives were performed using a power meter to assess the average current draw. I found that I was now able to travel at around 44 m per minute with the motor drawing 16 amps so I now had a maximum range of nearly 16 km (6 hrs) ! Not bad for an old Aquazepp !
Power meter used to asses battery usage post dive
Next on the improvement list was a rear handle like most other scooters have, the scooter needs two hands to drive comfortably in its standard configuration. A delrin handle and bracket was made and fixed to the shroud, a small PVC trigger box was welded onto the main body which contains a magnet and spring which are actuated by a lever on the trigger. This dramatically improved the comfort when scootering, its now easy to control with one hand and only needs light steering input to instigate a turn.
The scooter is now capable of running at different speeds, a 50 amp Syren brushed DC motor controller has been installed which is controller by an Arduino UNO. The sketch loaded onto the Arduino reads the output from a hall effect sensor mounted to the inside of the hull. On the outside of the hull in the same location is a small plastic rod with magnets embedded which can slide back and forth to increase or decrease the speed. Whilst noise is always going to be loud when using an Aquazepp due to the metal gears the motor seems to run better now it is being supplied through the controller. The speed as its currently set can be run anywhere between around 65 m/ m and 40 m/ m, this can be adjusted further on the surface by editing the Arduino sketch if required. The controller outputs a PWM signal and even running at my current top speed I’m not at 100% duty cycle yet but 65 m/ m seems fast enough for now if dive kit is worn, if snorkelling it is even faster !
The downside to using a variable speed over fixed speeds is monitoring battery consumption, with fixed speeds battery usage can easily assessed post dive and then used as reference in the future, with variable speed unless it is run at fastest or slowest then its hard to gauge where you have been on the scale.
