Framework Fabrication Details

By S.E.Moore -- Revised July 3, 2005

("McM" refers to McMaster-Carr catalog numbers)

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The ROVing Otter's external frame is made of 3/4", schedule 40, PVC pipe and fittings except for the motor mounts. The probe "K" is removable for easy transport of the ROV.

The dimensions given in the table are for the exposed portion of the pipe. An additional 1/2" to 5/8" was added to each end to insert into the fittings.

FITTING SIZE
TYPE (INCHES)QTY
TEE 3/4 24
TEE1 x 3/4 x 14
90 ELL 3/4 8
45 ELL 3/4 8
CROSS 3/4 2
CAP 3/4 1
REF LENGTH
CODEQTY(INCHES)
A55.25
B81.25
C66.50
D160.00
E43.75
F46.00
G21.25
H45.50
J25.25
K118.0
pvctools A PVC pipe cutter was used to cut the pipe to length. Since the pipe seating depth varied from fitting to fitting, it was most practical to first make up one joint, then measure and mark the desired length. Approximately 1/2" to 5/8" was added for the next joint.
pvcglue PVC cement was used for most of the frame joints. It is very fast setting allowing only 2-3 seconds to mate and adjust a joint.

Where more than one joint needed to be completed simultaneously a 2-part epoxy cement was used which gave 3-5 minutes of working time.
90jigarw A vertical work surface was setup perpendicular to the table top as an aid in aligning the joints.

Sections of pipe with extra fittings were temporarily inserted without glue (blue arrows) to insure that the ROV sub-assemblies were correctly aligned.
asmbits The sub-assemblies shown were prefabricated using PVC cement.
asm1 The end pieces were attached to the upper frame unit with epoxy cement (shown upside down).
asm2 The vertical members carrying the lateral lower frame pieces were next cemented on (shown upside down).
asm3 The lower end sub-assemblies were added again using epoxy cement (shown upside down).
asm4 Adding the front and rear base assemblies completed the frame.
boretee The four motor mounts were made from 1"x3/4"x1" PVC tees. The internal shoulders were first removed by boring.
bsawtee Each tee was temporarily attached to another tee for support while being cut in half on a band saw.
motormtg The motor mounts were finished by hand filing any rough edges .
tapcap 1" PVC caps were drilled and tapped with 1/4" NPT to receive barbed fittings for the motor wiring tubes.
fakemots Dummy motors made from short sections of 1" PVC pipe were clamped to the motor mounts temporarily during construction.
motcap The motor mounts were placed in position, but not cemented in so that adjustments could later be made to their orientation.
donefrnt The main enclosure was next attached to the vertical members with stainless steel band clamps.
donerear The front and rear faceplates were clamped in place with the tension latches.

A 2.25" diameter plastic cylinder served as a dummy Spare-Air unit during construction.