Tilt Reduction Mod

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Tilt Reduction Mod

Postby glnc222 » June 7th, 2013, 1:13 am

Simple Fitting Limits excess front/back tilt trapping Neato

[edit] this mod is needed for the "Bumper Lowering Mod" http://www.robotreviews.com/chat/viewtopic.php?f=20&t=17368
[edit] BotVac version added below http://www.robotreviews.com/chat/viewtopic.php?p=127169#p127169

Neato distinctively flips up the back when butting anything in reverse, from the suspension design. This tilt is so high it traps Neato several ways. When moving under furniture which fits over the turret, in a tight space the back can flip up against the overhead with pressure trapping the unit. The actual overhead clearance requirement is more like eight inches from the floor. Another case is backing up over obstacles high enough to grab the bottom in a way it cannot pull off.

The existing suspension lifts the rear up to 3 inches and the front 2 inches. Some tilt is necessary in order to move both forward and backwards over height transitions.
[edit] 3" rear tilt reduces front to back footprint length 1.25", which might assist in some tight spots; the smaller effect limiting tilt did not affect situations here. Only experience will tell.

[edit]see end of thread for simple thread loop method -- no hardware needed (not even sewing needle)
hidden bottom around end of the suspension spring, at case attachment

To reduce this tilt a mirror-mounting bracket from hardware was mounted on a 3/8" spacer 1" long in font of the wheel arm, screwed into the arm catch plate on which the arm rests fully retracted under weight. This plate has large strengthening ribs underneath.

The wheel well and post for the mirror-mounting bracket are shown here with wheel arm fully extended:
3/8" spacer and #6 screw for mounting tilt limiter

Wheel arm extension is limited by the attached mirror bracket:
tilt limiting mirror bracket installed

This length post reduces back tilt to 1 inch and front tilt to 1 3/8 inches. These sizes proved adequate for the floor transitions here. One quarter inch shorter definitely interferes with handling low transitions, especially backing up over low transitions. Reduced traction running on carpet is also a factor.

Special Requirements

A flat-head (counter-sinking) #6 screw is used for the conical head to fill the wider hole in the supplied mirror bracket. Wood or sheet metal screw for the soft plastic. 3/32" pilot hole. Depth 1/2" into the bottom plate, 1.5" screw. Neato is mostly assembled with self-threading sheet metal screws.

Sensitive clearances are present requiring the hole be perfectly straight and the post against the front of the wheel well, to allow the wheel arm full movement. The tight fit is shown in the photo. A wood block drill guide is recommended instead of just the spacer.
[edit] screw position used shown here:
screw hole position

The spacer is flush with the corner but the walls at the bottom, allowing for slanted walls. Marks the hole, but a guide is needed to keep bit vertical.
[edit] more drilling tricks: masking tape on the plate marked by a full shank width bit through the spacer for plate surface too hard by itself. A small indent drilled positions a bit run through a drill guide block.

no-drill option
An alternative to drilling into the case is epoxy gluing a 3/8" x 5/8" x 1" wood or plastic block against the front of the wheel well (bit of molding by the foot at HD). I've found such glue sort of pops off when pried, due to brittleness -- so may be good with warranties. A 5/8" wide indentation can be seen in the front wall of the well in the first photo. The screw hole is not centered in the 3/8" width, but slightly back, as the brush guard will extend slightly into the well over the top edge. The full width of the 5/8" slot is used to add gluing surface for strength, compared to 3/8 round spacers.
All clearances must be satisfied -- actually easier than the spacer, as the bracket can be used on top of the block to mark the screw position precisely, observing the fit to the wheel arm. Some sanding reduction of thickness to accommodate the glue layer may be needed. A 1/2" length screw can be used into the block. Such glued parts can be removed inserting a blade into the glue layer. Epoxy forms a brittle plastic layer. Do not use metal reinforced, possibly conductive, JB-Quick etc.

{edit] yet another method is to cut off part of a 1" steel right angle bracket, for the top, and glue or screw into the side wall of the wheel well. The spacer just saves sawing metal, and puts the screw in a reinforced plastic section, and allows different length posts.
[edit] if applying plastic from a drawer organizer to lower the bumper edge, a left over corner piece might substitute for the wood block. http://www.robotreviews.com/chat/viewtopic.php?f=20&t=16736 Being plastic might even fasten with removeable 3M Command adhesive strips (on two sides), though haven't tried. Has to hold at most 3lbs. [correction 1.5lbs newest measure]

stress measurements

Neato's 9 lb weight is divided about equally on four points: the wheel arm pivots on each side, and the wheel arm ends pressed on the blocking plate. The wheels are fully retracted when resting on the floor. At the plate the springs exert 2lbs of tension dividing the 4.5lb weight on each side about equally between the front and rear of the arm. The wheel arm swings down and the body tilts under at least additional 2lbs of torque pressure from the wheel motors added to the spring tension, to float the end of the wheel arm free. It is unlikely the pressure on the tilt limiting bracket is more than a couple pounds given how 2lbs of spring tensions must already be overcome by the motors to swing the arm out, but measurements could not be made of this net force.

software limitations observed

The traps observed had the wheels spinning on carpet without Neato moving. Especially when moving backwards the software appears to assume Neato is moving just from the wheels, and does not correlate with any lidar data.
The software appears to use a shortcut of using blocked wheel motion under power to fill the absence of a rear bumper. Poor traction with slipping wheels defeats this shortcut. It keeps trying to back up until the wheels are blocked from pushing the unit against an obstacle, which never happens. After continuing a couple minutes the run was terminated manually.

In moving forward, however, there appeared to be a time out on spinning the wheels, and Neato reversed out of situations after thirty seconds.

There is a possibility using the bristle brush on carpet may maintain traction better than continuous polishing with the flat beater. Traction seems to have fallen after a year of use. The precise cause is not yet determined.
The slider mod appears to solve the problem.

[edit]effect on other mod for lowering front bumper
With backward tilt reduced the corresponding downward forward tilt is reduced so down-extensions of the front bumper may not need a pivoting feature. "XV-11 bumper design and climbing"http://www.robotreviews.com/chat/viewtopic.php?f=20&t=16736

[edit] limiting wheel extension prevents the wheels-out microswitch sensors from closing, but the cliff sensors still tell Neato when off the floor.

other mods
Links to all mods I find (not just mine) are listed at http://www.robotreviews.com/chat/viewtopic.php?f=20&t=16475

[edit] The problem area helped by this under a cabinet also benefited from putting white masking tape on the inside, hidden part of dark furniture legs which the Neato was not seeing properly with the laser. It then does not bump the legs, showing how well it senses them. Much less thrashing around in the tight spot results.
Last edited by glnc222 on November 2nd, 2014, 8:43 pm, edited 7 times in total.
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Re: Tilt Reduction Mod

Postby glnc222 » October 25th, 2013, 12:12 am

coat hanger wire limiter

clip shaped from coat hanger wire

hooks into ribbed plastic plate above wheel


Needs a bit of tape with a flap under the brush guard to secure when not pressed by the wheel. The wire shown is not cut off as would the final form (should bend over parallel with the brush guard, close the square).

[edit] can be improved with more elaborate shapes. May be difficult to get the exact fit. The hook goes between ribs at the side.
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Re: Tilt Reduction Mod

Postby JEfromCanada » October 25th, 2013, 3:36 pm

Is this the type of item that could be created by 3D printer? Would it be strong enough for it's purpose if created in that fashion?
Current robots:
Roomba Discovery 4210 (R.I.P. - Freecycled)
Roomba 560 (retired)
Neato XV-11 SW version 3.1.17844, LDS version 2.6.15295, with Pet Brush and Vic's filter (sold)
Neato Botvac 80 SW version 1.1.97, LDS version 2.6.15295, Board SW version 22753
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Re: Tilt Reduction Mod

Postby glnc222 » October 25th, 2013, 6:01 pm

Too thin for plastic, only 1/16" wire, and has to be steel for stiffness. There might be a shape that would work, and could be in sheet metal or plastic. A sort of zig-zag plate, a right-angle bracket with one end bended, might fit with a screw sideways as the hook under the ribbed plate, and a thick end stand into which a rotating piece can be screwed as the holder similar to the mirror mount.
1/16" steel rod in some hardwares, and ebay metal dealers. Small sheet metal plates are in Ace.

[edit] lot of subtleties in this wire shape to fit. The plate has three 1/8 wide ribs underneath, with the hook bending inward to the center opening, keeping the top branch against the side. There is also a narrower opening to the side too thin for the wire. It's much more straightforward to glue in a wood block to screw on a mirror mount. A proper sheet metal piece could work, but time consuming to make. I just examine every possibility.
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Re: Tilt Reduction Mod

Postby glnc222 » October 26th, 2013, 3:00 pm

Other possible methods
Just to show this mod is practical, multiple methods have been considered.

tie down thread
One of the wheel arm case screws is at the swinging tip. A thread can be attached to that and hooked into the tension spring above (below when the unit is upside down for servicing). The spring attachment screw is right there but not quite reachable without opening the case, so just hook into the spring close to the end, where there is very little slack or play. (Oldest Neato's attach the spring to the case bottom; late 2011 strengthened and moved to the top cover with a screw instead of plastic nub, correcting breakages of the older fittings).

The optimal holding position with the mirror mount puts the center of the wheel axle at the bottom edge of the case, big shiny end visible from the side.

Command Adhesive
There is clearance on the outward side of the wheel to Command Strip glue thin plastic or metal over a large area of the case inner side (compared to the wheel almost scraping the other side). An integral right angle bend flat piece across the wheel butting plate under the round spacer used with the mirror mount, through which a #6 flat head bolt could be put with the nut on the mirror mount end. Tape over that flat around the inside surface of the ribbed plate to add hold-down on the opposite side. A way to use the mirror mount without drilling or gluing the stanchion. Probably one Command Strip sideways or an extra underneath, for sizing.

Minimal thickness should be added to the wheel butting plate as that extends the wheels outward. Such thin material like 1/32 plastic or metal will not be stiff enough itself but can be secured around the plate structure side and so on. Sheet metal, by the way, is abundant on soup cans. The tool to cut it is something else.

Contact if any more detail is needed.
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Re: Tilt Reduction Mod

Postby glnc222 » October 26th, 2013, 5:42 pm

Thread Loop Detail
hidden loop bottom is around end of spring at its case attachment

Thread loop (no hooks) around end of suspension spring and screw in wheel arm.
Heavy duty, "button and carpet" thread required.

Open the rear bottom vacuum cover, four large screws, to access the wheel well and spring. Unhook the wheel from the spring for feeding thread around the spring (pull shaft end slightly forward to release, twist out), pulling thread back to the case attachment screw,behind coil. ( [edit] more detailed wheel pics in "disassembly precautions" http://www.robotreviews.com/chat/viewtopic.php?f=20&t=16021&p=107467&hilit=disassembly+precautions#p107467)
Reattach spring and mount wheel in place. Use tape to secure the wheel in position with the drive shaft centered on edge of the case.

Unscrew the wheel case tip screw slightly to allow wrapping a couple turns of thread.
Tie off thread with wheel held tightly. [edit] remove the tied loop to duplicate for the other side more easily off the unit if preferred. Slack when tying thread may require holding the wheel a bit lower when working; finished should hold the wheel with the drive shaft centered on the case edge under spring tension, how the mirror mount method on 1" spacer ended up.
Caution reattaching spring: careful not to scrape off the fragile levers on the microswitches under the pivoting end of the wheel arm; hold down with a screw driver if necessary while reinserting the pivot shaft. These detect wheel extension for the "put me down" message on the LCD, along with cliff sensors.

Cut thread to remove. Or unwind from wheel screw, slide loop off unhitched spring or leave inside.
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Re: Tilt Reduction Mod

Postby glnc222 » November 2nd, 2014, 8:42 pm

BotVac Version

[edit] screw shown below is on top of the assembly only on one side, underneath on the opposite side. So use tape only per following post.

A strip of duct/duck tape applied inside the wheel well and tied with thread (or by itself) to the top end screw on the wheel arm, size T8 Torx screw (not visible in many photos because anodized black). The holding strip is vertical under tension for maximum sheer across the tape glue area. No need to open the case. A thread loop is best for removal as the screw wraps the tape around unscrewing. The tape sticks over 1.5" deep sides in the wheel well and the extension is folded over self stuck together. The wheel is limited with the axle aligned with the case edge.

For adequate hold inside the wheel well the tape must wrap around the sides of the wheel seating block and the tang up over the wheel be half and inch on the inside corner, so more tape extends out to the side, with a wider tape to hold the pull on the tang. It has held up well now for a dozen runs. Use the waxy backing of stick on labels to cover the tape while maneuvering into position, then pull off and press the tape with a screw driver.

duck tape strip limiting wheel arm extension

tape inside wheel well
Last edited by glnc222 on December 27th, 2014, 4:13 pm, edited 2 times in total.
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Re: Tilt Reduction Mod

Postby glnc222 » November 12th, 2014, 4:18 pm

Botvac correction -- screw only on one side

The Botvac wheel assembly is identical both sides and just turned over opposite sides, so the screw shown prior post is available only on one side, at least with disassembling the whole case to reach underneath the wheel arm.
So tape can be used over the top of the wheel arm instead of tying to the screw.

tape over top of wheel arm limiting tilt

The tape glue must fact opposite directions at the two ends, similar to this photo:


See above post arrangement of tape around the seating block for proper hold.

Cut 5 in. of 2-in. wide duck tape. Cut into 1 in. strips. Cut one strip 2 3/8 in. 1 3/8" fits onto the block face in the wheel well, some around the side for more hold. Stick the strips together overlapped the other 1". Trim the width of the tail to 1/2 in. aligned with the top surface of the wheel assembly. A 1/16" turn in at the end makes a handle to pull off if wanted. The several inches over the wheel arm may hold well enough over time, will have to see. Pretty good stick with duck tape and there is very little arm swing.
I suppose if the case is opened, thread could be fastened to the screws and retained through the joint between the top and bottom case halves, without glue. See the mods list top of main page for Botvac opening, video.

[edit] Using Duck Tape -- the backing of mailing label forms and such has a waxy surface to which tape does not stick. Might be used to keep Duck Tape manageable while installing the wheel well with all the obstructions. Pull out after getting the tape down where needed, then press in with screw driver or the like.

[edit] The thin strip over the wheel will hold best position onto the block below at the outside edge, at the wrap-around corner, than if on the inside edge of the well. On the inside it is pulling on the exposed side of the tape down under, and can peel it pack; more hold at the corner with tape around both sides of the block, pulling on the center of the tape wrapped around.

[edit] Gorilla tape found much better than regular duck tape for this. The strength is needed and the glue has a smoother consistency, maybe more like gaffer's tape. Regular duck tape will come apart after three months in this use.
Last edited by glnc222 on October 18th, 2015, 2:58 pm, edited 1 time in total.
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Re: Tilt Reduction Mod

Postby DogHairCleanUp » January 28th, 2015, 5:10 pm

Why doesn't this have to be used with just a cardboard strip? Which method did you use with the plastic tray? Would reducing the tilt make the plastic parts wear out faster? It sounds like I'll have to get a bungee cord. Something that should be simple, gets complicated so fast.
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Re: Tilt Reduction Mod

Postby glnc222 » January 28th, 2015, 6:56 pm

The same mechanical actions apply to a cardboard strip.
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