ACCESSING DISCO'S INTERIOR
Access to Roomba's interior, as well as re-assembly, has been found to differ
between Roomba-Discovery models. The main discriminating feature is the means by
which Disco's lifting-handle is attached to the robot. Discos which sell for
lower-prices have the handle secured to Roomba's Top-Cover, while the other
models have been designed such that their handles hinge from the outer-Bumper.
Those differences in construction can be visually detected by simply looking at
Disco's top side; since, it is easy to tell whether the handle is Cover-mounted, or
That difference in handle-mounting is the external, visible discrimination
feature which serves to identify machines that have concomitant
internal features that work together to make removal of Bumper and Cover
relatively difficult for the Bumper-mounted Handle robots, and easier for the
Cover-mounted Handle robots. If you are interested in seeing some detail of
those internal features (recommended for someone working on a Bumper-mounted
machine) take a side trip to
Cover / Handle Interface.
In short, the above paragraphs say that we have two classes of Roomba to
consider, those that need a little more attention to the Bumper & Cover removal
process, and those that don't. Existence of that difference requires these
disassembly steps be presented in the form of two options, "HoB",
Handle-on-Bumper, and "HoC", Handle-on-
If you now know you want to follow the HoC option take this
Handle-on-Cover link; otherwise read on to the HoB
HoB: Outer-Bumper and Roomba-Cover Removal
All Bumper and Cover
must be removed before attempting dismount
of either subassembly. The two subassemblies must mechanically disengage Chassis
fittings as a set; at least for the first few millimeters of movement.
Steps in HoB apply to the following Discovery models, in which the
Handle is mounted on the Bumper and interleaves with the Cover:
- Roomba-Discovery, #4210
- Roomba-Discovery Replacement, #4211
- Roomba-Discovery SE, #4220
- Roomba-Scheduler, #4230
Note: We (Rog is helping) have not had hands-on experience with the Discovery
SE, or Scheduler models, but those bots are considered mechanically
identical to the #4210 Discovery, which is known to reward owners when the
HoB process is used.
Models #4210 and #4220 that were produced prior to, roughly, mid-2005, came
with some removable parts that are called "Fender Skirts" in these documents. It
can be useful for an owner to recognize whether his Roomba has Fender Skirts,
because their presence provides much easier access to the drive-wheels; and
also explains why two very long screws are used just forward of the drive-
wheels. The image below has pointers to the joint features which indicate
presence of a Skirt.
A Fender-Skirt is a removable panel which spans the distance between those
joints. Roomba-owners who purchased either of these Discovery models after
mid-2005 should inspect the left and right sides of their bot to see if "Fender
Skirts" exist on their particular unit. If no Skirt-joints are visible, no Skirts
exist on that Roomba.
HoB: Mechanical Disconnects
To access the interior of a Discovery #4210, Remove the Bin assembly, then turn
Roomba on it's back and remove the Brush-Guard, Main-Brushes (with
end-bearings), and Battery. Place removed items clear of the work area.
- Remove 4 Bumper screws.
- With the front wheel nearest you, look at the bumper's bottom edge and note
the four screws, marked "Bumper" in the following image (and that are all in
half an inch deep holes) two just in front of the twirly brush and two the other
- Undo (#1 Phillips bit) the four screws, and turn Roomba over momentarily so they fall onto
your workbench.(hopefully covered with a towel, to stop them bouncing).
- Put the four screws somewhere where they won't get lost, and note that they
are slightly, but noticeably thinner than the other screws you are going to
remove, so don't mix them up.
- Remove 8 Cover screws (#2 Phillips bit), and Dislodge the Cover.
Now for the main lid (Roomba-Cover)... here is a visual-aid of Cover attachment
points, where screws must be removed:
- With an upside down Roomba with its front-wheel towards you, note the two
screws that are between each tip of the black bumper and the front of each side
- If Disco is fitted with removable Fender-Skirts (which is why these
screws must be long) these two screws need be only loosened by four turns
(each will stay with its Skirt), and the Cover will no longer be connected at
those two points. With Skirts, those screws are both about 13-mm long, and so
are different to all the others in this set of eight. Without Skirts present,
they are all the same length.
- Next remove the two screws each end of the battery cavity.
- Then the two screws deep down in front of each end of the black brush-deck
(positioned between the screw you just took out and where that long screw was).
- While working this left-right row, take a look at mid-span to verify there
is no screw in a central position. If one is found, it should also be removed.
- Then, look at the back end of the Roomba and each side of where the Bin
fits, you will see a screw that is sunken deeper in a hole than the other two
screws you will see...remove ONLY the two sunken screws....invert Roomba and
shake the screws out.
- From the main lid you should have six short screws and two long ones, count
them to make sure they are all out [unless two remain in their Skirts, or one
was found at the center of the brush-deck cavity], then proceed....
- Put the eight screws somewhere where they won't get lost, and note that they
have differing lengths, so use a memory-jogging scheme to store them, a scheme
that will ensure they go back in the same depth holes from which they came.
- Separate the Inner & Outer Bumper-sections.
- With Roomba back to inverted, put a finger under the left-side, black-bit of
the bumper just in front of the fixed, wheel-protecting brush, and with thumb or
the other hand, push the grey bumper downwards to dislodge it. Here is a visual
hint (but happens to be a view of the right-side features):
- Repeat this on the twirly brush side by sticking your finger in the cavity
that is on the twirly-brush side, just outboard of the square, silver looking,
charging-pad, and pushing the grey bumper downwards as before. The grey bumper
cover should now be loose, and we now have to disconnect
HoB: Bumper Electrical Disconnect
While holding the loose external-bumper, invert Roomba and place it on it's
wheels again, facing away from you. The following steps should safely de-mate
- Carefully lift the Bumper and look underneath it. At the front and in the
middle you will see a small connector with seven wires, and tiny little "ears"
("Ledge", in the photo) at each end, next to the wires -- Note that the
connector can only be connected one way around....more about that later. Here is
what should be seen:
- Carefully, lightly, "pick" one ear (or "ledge") downwards with a fingernail,
and move it a tiny bit, say 2 mm. Then "pick" the other ear and move it about
the same amount. Repeat this, and the connector should slide down and apart with
gentle wiggling, not much force is required (you are trying to slide the
connector apart evenly, without bending the pins), just be gentle and patient.
- When the connector is out, do not attempt extracting the Bumper (wait for
additional instruction), however, note that the bit of the connector fitted to
the external-Bumper has a sort of gap, or window that lets you see the pins and
the other half of the connector has cast on ribs that fit into this gap, as
This is what stops the connector being connected the wrong way round, but BE
WARNED we are sure if you really tried very hard, you could ham-fistedly manage
to force it together the wrong way round, so make sure you don't! The wire
colours starting at the left are: red, blue, black, white, blue, red, brown.
HoB: Roomba-Cover & Bumper Mechanical Separation from Chassis
Put Roomba back on It's wheels, facing away from you this time, then:
- Since no screws are retaining the Cover, gently lift it away from the eight
chassis' sockets by lifting the Cover and pushing down on the Chassis at a
sequence of points around the rim. Do not plan on lifting the Cover very far, it
has a cable fastened to the chassis, or hooked to the chassis; and its forward-
facing 'prongs' will still be engaged with bumper parts.
- With the Cover now free to move upward, attention must be shifted back to
the external Bumper assembly, since its needed upward motion will not be blocked
by the prongs of the Cover. Start at the left end of the Bumper, and lift it
vertically. Wiggle it as necessary to slide apart the engaged screw-bosses. Here
is a view of those bosses (as seen after Bumper & Cover dismounts):
As lifting causes the wanted separation, allow the Roomba-Cover to elevate to
the extent useful, and work your way around to the right-end until the Bumper
assembly can be taken away.
- Store the Bumper away from the work area.
The Roomba-Cover will next be disconnected and removed from the assembly.
In preparation for that work, Rotate Disco end-for-end, so it faces you, right-
HoB: Roomba-Cover Electrical Disconnect & Removal
- There is another connector to disconnect, this time its what's known as a
ribbon cable and goes from the control-buttons in the Cover to the main
processor board. Lift either the forward Cover-edge, or rear edge, and view the
ribbon-cable, following it to the where it is secured to the chassis' main,
left-right bulkhead. The cable may be found spot-bonded with HMG,
(hot-melt-glue) to a shallow channel-shaped notch, e.g., ```|__|```, or simply
fitted into a 'lazy-C' (see the photo) pass-through with hooks at its top, along
the upper edge of the indicated bulkhead.
- Remove the cable from that tie-down point. The scene should
look like this:
- If the service-loop in that cable permits it, carefully flip the Cover over
and lay it down on the Chassis Assembly, so it appears this way:
That operation greatly enhances access to the cable-connector.
- De-mating this one can be the same deal as before.....gently flick the ends,
and note that the holes and cast-on lumps (a rib on each narrow end-face that
get it the right way round) are much smaller and daintier this time, but once
again they should still work, especially if you use your brain.
- Also take note that friction-force of engagement is more than twice that of the
Bumper's connector (16- contacts here, vs. seven there), so not everyone's
finger nails may be up to the job.
- Some sort of special connector de-mate-tool can make the task very much
easier in such cases. Two useful de-mate tools are described in
- After the connector's de-mate, remove the Cover to safe storage away from
the work area.
It should now be clear, that full access to any electro-mechanical subsystem
is readily available. Attention may now be directed to that task which required
access to Roomba's interior.
As time permits, such as the interim while waiting for a shipment of parts
from Mouser, or for some epoxy to cure, you may wish to follow some tips for
making adjustments to plastic edges that will aid assembly, and aid future
disassembly, of the Cover and Bumper. If so, take this Tips
Then, assuming you have no interest in the HoC steps, you may return to
the Index page.
HoC: Outer-Bumper May be Removed First, Then the Cover
Bumper and Cover assemblies may be removed only in this sequence: Bumper
first, then the Roomba-Cover. Using this HoC, all Bumper and Cover
may be removed as a single step, or just the Bumper's four screws
may be taken out before dismounting the Bumper; however, if Roomba-Cover screws
do get removed at this point, the Cover may remain in intimate contact with the
Chassis until the Bumper has been dismounted.
HoC steps may be applied to the following Discovery models, in which
Disco's Handle is mounted on the Cover (rather than to the Bumper):
- Roomba-Red, #4100
- Roomba (Sage), #4105
- Roomba, Pink-Edition, #4188
Note: None of the authors have had hands-on experience with the Pink, or Sage
models. Those models have been placed in this category because they appear to
have the same construction as the Roomba-Red Discovery.
HoC: Roomba-Bumper Screws Out
The external Bumper has to be removed first, before the Roomba-
- Prep work area. Clear several square feet of area on a work-surface, and
arrange some sort of storage means for the various fasteners that will be
removed. Several levels of grief may develop when Roomba fasteners are either
cross-mixed, their proper usage is uncertain, or they have been lost.
- Prep Roomba by removing its battery, the Brush-Guard & Main-Brushes, and the
Bin; then set those items away from the work area.
- Invert Disco onto a clean, soft-material placed on the work surface, and
notice the locations of the four screws marked in this photo.
- Using a #1-Phillips driver, remove four-each Bumper screws marked "BUMPER".
- Momentarily invert Roomba to let screws drop from deep recesses. Label and
store the four identical screws.
HoC: Bumper Mechanical Disconnect
At this point the external Bumper subassembly is no longer bolted to the black,
internal-Bumper subassembly, but the two are held together by a pair of tongue
and groove, or knife & fork type features, one at each end of the Bumper, and also by
friction-fits and long engagements within the four screw-bosses. There is also a
cable-connection to de-mate. Steps follow to achieve mechanical disengagement --
the idea is to push the gray Bumper vertically downward, relative to the Chassis
Here is a stepwise list:
- Disco is belly up, and its tail is away from you. Separate the knife & fork
clip at the left Bumper-end first. Here is what this "knife & fork" interface
looks like (which happens to be a view of the right-side features, and shot
without the Chassis in the way). Notice placement of a the little-finger-tip
under end of the black assembly to lift it (as well as the rest of the Roomba
Chassis), while the thumb is set to push down on the edge of the gray Bumper.
Note: The black-casting ("internal Bumper") has been re-designed (ca., 2005,Q2),
to apparently reduce the amount of material in it. That mass-reduction also reduced
available places to place the little finger, hence the very end of the
black-casting was chosen as the alternative.
Once an appropriate finger-hold has been obtained, use the thumb of the same
hand to press the nearby edge of the gray Bumper, pushing it downwards against the
lift of your finger. This action should disengage the near end of the bumper
without excess stress on the plastic parts.
- Move your grasp along the displaced Bumper parts and keep applying the
vertical force between the two parts. Separation should continue to increase.
- When hands reach the right-hand pair of screw bosses, use your right hand to
maintain the current state of progress, while your left little-finger and thumb
repeat the above knife & fork separation at the right end of the Bumper.
Note: Many words have been used to describe this process, and 'minutes' will be
needed to read them, first time through; however, the actual process of doing
the work takes only tens of seconds! Further, if re-assembly tips pertaining
to the Bumper and Roomba-Cover are followed, these subassemblies will
practically fall apart when given a little push! See Tips.
- If the Bumper is not fully separated from the black portion, continue
displacing to disengage all screw bosses. Screw-bosses can telescope within each
other as much as 18-mm engagement!
HoC: Bumper Electrical Disconnect
- Position Disco upright, and with its front oriented away from you.
- Grasp the rear edge of the gray Bumper, push it forward (away from
you) slightly, and then elevate it so you see the flat-cable and seven-contact,
cable-connector shown in this photo. Notice the marked ledges, at left and right
ends of the lower connector half, the portion you will next disconnect from the
- Using whichever fingers work best (middle ones seem to do well), position
finger-nails on those ledges and apply a downward force on one ledge. After it
moves about one or two millimeters, shift the force to the other ledge, and
repeat the displacement. After alternating, back and forth, a few times, the
connector and cable will fall loose. Note: The goal is to do a de-mate without
bending any pins, and without pulling any harness wires out of its
cable-plug-cap. Never pull on the wires.
- Inspect both connector bodies. Notice the large, centered-notch in the PWB-
mounted receptacle portion (in which five pins can be seen), and find the
matching guide-ribs on the plug-part. Those are the polarizing (keying) features
which will ensure never doing an incorrect mating of plug-cap to receptacle.
- Pull away the gray Bumper assembly, and store it in a clean and safe area,
until it is needed.
HoC: Roomba-Cover Disconnect
Appropriate instructions for Cover-screws removal are given next, and include
identification of the central thread-forming-screw which seems to be used only
on the Discovery-series models which hinge the Lifting-Handle from the
Roomba-Cover. Notice the marked screw-locations in the following image.
If not previously done in support of Bumper removal, screws which go into
the Roomba Cover, must be removed at this time. Invert Disco and using a #2
Phillips driver, remove eight-each screws marked "C", and the single
central-screw used on Roomba-Red, -Sage, and -Pink (or any similar Handle-to-Cover
constructions). Typically these screws all have the same major diameter and
pitch, but they do vary in length, so carefully catalog them, so you know where
to place the various lengths when re-assembling, and then store the screws.
HoC: Roomba-Cover Removal
All fasteners have been removed, but the Cover may seem securely attached. As
with the Bumper, the socketed screw-bosses have sufficient friction of
engagement to hold the Cover onto the chassis assembly. None of the overlaps are
deep, but there are twice as many as in the Bumper. Like the Bumper, the Cover
is also tethered to the chassis-assembly by an electrical-cable. The following
steps will get the Cover off:
- Use finger force applied between the Cover's inner surface and the chassis
structure to free a couple boss-engagements. Shift the force to another rim area
of the Cover, and repeat. Work your way around the circle until all eight, or
nine screw-bosses have been disengaged.
- Lift either the forward Cover-edge, or rear edge, and view the ribbon-cable,
following it to the where it is secured to the chassis' main, transverse
bulkhead. The cable may be found spot-bonded with HMG, (hot-melt-glue) to a
shallow channel-shaped notch, e.g., ```|__|```, or simply fitted into a 'lazy-C'
(see the photo) pass-through with hooks at its top, along the upper edge of the
indicated bulkhead. Remove the cable from that tie-down point. The scene should
look like this:
- The Cover's cable is still connected, see if enough service length is now
available to carefully flip the Cover over and lay it down on the Chassis
Assembly, so it appears this way:
That operation greatly enhances access to the cable-connector.
- Next, the 16-contact Roomba-Cover connector must be de-mated. The end-ledges
on this plug-cap are incidentally 'shielded' by adjacent components, thus making it
difficult to apply force to the ledges with finger-nails, or even by common bench
tools. Although one of the authors claims to be able to do the finger-nail
disconnect of this connector, this de-mating task is perhaps best done with a
special pair of forceps. If interested, see descriptions of two workable
- Using the tool, as just discussed, along with the de-mate motion used on the
Bumper's connector, the Cover's connector can easily, and safely, be worked
free. This would be a good time to look at each end of the plug-cap, and notice
the offset ribs molded onto the narrow end-faces of that cable-connector. Those
ribs enter matching slots which can be seen at each end of the PWB-mounted
receptacle. Ribs and slots are polarizing features which prevent you from mating
these two the wrong way.
- Store the Roomba-Cover with the Bumper. It should now be clear, that full
access to any electro-mechanical subsystem is readily available.
Attention may now be directed to the task which required access to Roomba's
interior, hence this would be a good time to get on with it!
However, when time permits, such as the interim while waiting for a shipment of parts
from Mouser, or some applied epoxy to cure, you may wish to follow some tips for
making adjustments to plastic edges that will aid assembly, and aid future
disassembly, of the Cover and Bumper. If so, continue reading; else get outta
here and go do useful things!
Tips to Ease Bumper & Cover Re-Assembly
As preparation for re-assembling the Roomba-Cover, and the gray Bumper, to
the Chassis Assembly, the benefits obtained by performing either one, or both of
the following de-burring and lubricating tips can be well worth the effort. You
may find that screw-bosses, which have been treated as described below, simply
jump into proper registration by themselves, if placed within a couple
centimeters of each other!
De-Burr Those Screw-Bosses
There are two geometries to consider here: Crisp edges at the ends of male
pillar-like, screw-bosses, and female-socket entrances which accept those boss
ends. Its getting a little sexual at this time, so to put this into proper
perspective lets view a photo of these mechanical features. Here is a view of
Only minor modifications, and therefore 'effort' need be done, they are:
- Using your S.O.'s "Diamond Deb" (brand name) finger-nail file, abrade away
any burrs (i.e., molding "flash") that can be felt on any of the Roomba-Cover's,
or Bumper's screw-boss ends. Finish up by chasing the file around the end
(holding the file at an approximate 45-degree angle) to form a slight
edge-chamfer. A picture is worth a thousand words:
- Then, to do the inverse trick on the counter-bore entrances, a very sharp
cutting edge should be held to an angle between 40 to 50-degrees (wrt the
screw-hole's axis) and run around the entrance to eliminate the crisp 90-degree edge
found there. Most likely, the tool of choice will be the acute-angled, #11 blade
manufactured by X-ACTO. Many other cutter types could alternatively be used. In
particular, for those recesses having a full-circle (uninterrupted) entrance,
appropriate diameters of 82-degree counter-sinks can make the chamfering job
a quick one. Here's a view of the chamfering via knife:
Lubricate Those Screw-Bosses
After chamfering the ends of all screw-bosses (those which generally contain
the screw-thread) run a bar of wax around each cylinder, to wax-coat a short
region (3 to 5-mm) near the end of the boss. Candle-wax, or canning-wax (paraffin-wax)
should be easy to find in a household.
Chamfer Half-Laps At Tails
There are two pairs of crisp edges at the left & right tail ends of the
Cover and Chassis which can be modified to ease their re-engagement. Here is a
sequence of engagement views of an outer feature of the Cover, showing how it
slips into a matching recess in the Chassis:
And, while that outer engagement is going on, the following inner engagement
must also be taking place:
While the Cover is being fitted back onto the Chassis, the above illustrated
edges tend to 'hang up' and fail to readily overlap. Inattention to this fit-up
detail can result in the inability to later install the Bin, simply because the
Chassis walls have been pushed together enough to make the opening narrower than
the Bin's width! Appropriate chamfering can assist with the fit up, and help avoid
- Again, using your S.O.'s "Diamond Deb" finger-nail file, abrade an
approximate 45-degree angle edge-chamfer along the lower edge of the Cover,
here, and on the right-side too:
- Then, do an internal chamfer along the Chassis as shown next. In this view,
a very sharp knife edge is held with its blade set perpendicular to the run of
the edge, but tipped to an angle between 40 to 50-degrees. As the blade is
moved along the edge, a small amount of plastic is scraped off to form the
chamfer. Other cutter types could alternatively be used.
Here's a view of the chamfering via knife:
Be sure to do the left side too.
- Moving to the Bin-side of that tail-area, the upper-edge of the Brush-Deck's
pivot-block (which on this RH-side, also carries the female electrical
connection for the Impeller-Motor) should be chamfered enough to break the sharp
edge. The Diamond-Deb file can work well here. The edge-zone that needs work is
shown inside the oval balloon:
Remember to chamfer the similar edge on the left-side of Roomba too.
- Similarly, on the Roomba-Cover there is an edge which slides by the edge
just treated. Filing a chamfer on this edge can be done, but file-motion
would be limited to very short strokes. Instead, a sharp-knife is recommended;
and the next illustration shows how it should be held, firmly, while stroking it
along the edge:
Remember to chamfer the similar edge on the left-side of Roomba too.
That work concludes the adjustments which can aid fitting the many tight
interface spots on these plastic-casting's back together.
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This page is currently maintained by G. Plews