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Nose Gear Lessons Learned

Walt

Well Known Member
Given the recently reported nose gear leg bolt failure, a few of us “VAFers” have concluded that the time has come to summarize “Nose Gear Lessons Learned” at least from our personal perspectives and in the interest of safety for our fellow VAF RV-A builders and fliers. We are talking about improvement, prevention, and safety; not any inherent flaw in the RV-A nose gear design.

Post Contributors (in alphabetical order): Walt Aronow (“Walt” on VAF, RV-7A), Bruce Hill (bruceh, 9A), Bill Palmer (same, 8A in-work), Bill Pendergrass (rzbill, 7A), and Alex Peterson (AlexPeterson, 6A).
(I want everyone to know that even though I am the one posting this, these other guys did most of the work putting this document together!)

Applicability: RV-6A, 7A, 8A, & 9A

Disclaimer: These “Nose Gear Lessons Learned” are opinion-based, consensus recommendations based on the personal perspectives and experiences of those individuals contributing to this post. These lessons are deduced from our own experiences and the experiences of others as reported on VAF and are not as the result of definitive engineering studies, testing, or similar professional analyses. These lessons learned do not represent the recommendations of Van’s Aircraft except as noted in Van’s published Service information (bulletins, letters and notices, and revisions and changes . . . see the included links). In other words, as an RV-A builder or flier, it is entirely your personal decision whether to acknowledge these lessons learned or ignore them.

Link to Van's SB page:
http://www.vansaircraft.com/public/service.htm

LESSONS LEARNED (RECOMMENDATIONS):

1. Installation

Make sure that all nose gear components are installed correctly.

For example, the stop collar (flange) can easily be installed backward which severely limits nose wheel castering and can create high shear loads on the nose gear leg retainer bolt. If you can visually check the stop collar easily, we recommend referencing Van’s installation drawing for proper stop collar orientation = stop tabs (arms) forward.

NG5-L.jpg


Sheared leg retainer bolt from incorrectly installed stop collar:

boltfail2.jpg


We highly recommend performing Van’s new Service Bulletin to check the stop collar orientation before further flight:

http://www.vansaircraft.com/pdf/sb14-12-22.pdf

All of the nose gear system components are subjected to high loads, so pay extra attention to correct installation. We recommend carefully checking the entire nose gear system for proper installation, operation, and adjustment. High-quality workmanship is important!

2. Nose Gear Fork

If you still have the older-style nose gear fork, Perform Van’s Mandatory Service Bulletin 07-11-09 (Nose Gear Leg and Fork Upgrade)

http://www.vansaircraft.com/pdf/sb07-11-9.pdf
http://www.vansaircraft.com/pdf/Nosegear_sb_faq.pdf

NG6-L.jpg


Read these Van’s Service Letters:

http://www.vansaircraft.com/pdf/Nose_gear_service_letter.pdf
http://www.vansaircraft.com/pdf/letters/nosegear.pdf

3. Nose Wheel

Replace the Van’s-supplied Matco nose wheel with an improved Grove, Berringer, or Modified Matco (Anti-Splat Wheel and Bearing Modification) wheel. Reasons: Lower rolling resistance; reduced nose wheel shimmy. Periodically (at least annually) balance the wheel/tire assembly and check the tire for roundness. Replace/rebalance the tire as necessary.

Matco Wheel Alternative: Carefully and frequently check the Matco Nose Wheel Axle Torque per Van’s Service Letter:

http://www.vansaircraft.com/pdf/Nose_W_T.pdf

Goal: Reduce/Eliminate Wheel Binding and Shimmy.

Comment: The reason that we are recommending changing or modifying the Matco wheel is that many RVers have had difficulty properly installing, lubricating (packing), and adjusting (torquing) the combination of the nose gear fork, 3/8-inch axle bolt, and Matco wheel system (wheel, roller bearings, and cones/mushrooms). Without a perfect installation and frequent, proper adjustment and lubrication, this fork and nose wheel system is prone to perhaps exhibiting bearing binding or even lockup. Proper alignment and stacking of the Matco wheel system to the nose gear fork is not easy, the roller bearing preload is set by the axle torque, and the axle is relatively flexible. We highly recommend installing a nose wheel system which completely separates the bearing preload from the axle torque. A more rigid axle is recommended as well.

Note: Earlier model 6A’s had a more rigid design axle from Vans as shown:

Nose%20Gear%20Old%20and%20New-M.jpg


4. Nose Gear Leg Retaining Bolt

Periodically (every annual or more often if operating off rough fields), carefully inspect the nose gear leg and engine mount connection.

(1) Per Van’s drawing, check to make sure that a washer is NOT installed under the head of the retaining bolt. If a washer is installed under the bolt’s head, the bolt’s grip length does not fully contact the engine mount at the bottom. If you insist on installing a washer under the bolt head, the next longer bolt will be required; probably with two washers at the base to avoid showing too many threads beyond the lock nut.

(2) Lift the nose wheel off the ground and check the nose gear leg for play (gear leg movement at the engine mount socket). If some play is observed then remove the AN5-20A nose gear leg attachment bolt and inspect the bolt and bolt hole for wear.

Note: AN5 bolts can have a diameter as low as 0.309. If you have a “slightly loose” nose gear leg either upon initial fabrication or at a periodic check, you might try installing a close-tolerance AN175-20A or NAS6605-26 bolt instead. Note: The NAS6605-26 is specified, because its overall length is the same as the AN5-20A. The -25 (same grip length as the -20A) is too short.

If the engine mount’s bolt hole has been enlarged such that the AN5 (or AN175/NAS6605) bolt is no longer a “close fit,” enlarge the hole slightly (ream) and install an oversize NAS 6605-26X (+.0156 inch) or NAS6605-26Y (+.0312 inch) bolt. The appropriate reamers from Genuine Aircraft Hardware are, respectively, the straight-shank PPR-.3261 (for -X) or PPR-.3417 (for -Y). Both reamers have an approximate 2-1/4-inch flute length with a standard 0.309-inch diameter, 9/16-inch long pilot. Threaded shank versions are PPRT-.3261 and PPRT-.3417. Optional reamers are the PPRL-.3261 or PPRL-.3417 with a 3-inch flute length; same pilot.

Note that oversized NAS6605 bolts still have standard 5/16-24 threads, so standard AN960-516 washers and AN363-516 (MS21045-5) all-metal locknuts fit the oversized bolts.

Note that Van’s Aircraft has not approved the installation of an oversized NAS bolt, but flying with a loose nose gear leg is definitely not recommended!

Technically, the only approved Van’s Aircraft solution for fixing a loose nose gear leg would be to repair (weld and drill) or replace the engine mount and continue to use an AN5-20A bolt as specified. This assumes, of course, that the hole in the nose gear leg itself is not enlarged. If this hole is also enlarged or damaged, the nose gear leg would need to be replaced to remain within what is currently published by Van’s Aircraft (the original plans and drawings).

Con't next page....
 
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Nose Gear Lessons learned - Cont'd

5. Breakout Force

Periodically (every 50 flight hours or less), check the nose gear lateral breakout force (22 pounds MINIMUM at the wheel axle). Many RV-A builders/fliers set the breakout force at 24 pounds.

Goal: Reduce/Eliminate Wheel Shimmy.

Note: Slightly lapping the outer contact edges of the two Belleville (spring) washers usually helps in the adjustment and retention of the breakout force (increased contact area).

6. Tire

Every time you fly, pay careful attention to proper tire inflation (35 psi recommended). Check the tire condition and replace the tire or tube as needed for safe operation. Check the pant-to-tire clearance considering tire deflections under load. If needed, modify the wheel pant for adequate tire clearance.

Tip: Use LOTS of talcum powder when installing and inflating the inner tube to make sure that the tube is not sticking, distorting, or folding against the inner wall of the tire. Also, make sure that the valve stem is properly positioned and not under any side stress. An improperly positioned or seated inner tube can be a strong contributor to tire imbalance, out-of-roundness, and nose wheel shimmy.

Note: Tire pressure and nose wheel shimmy can be indirectly coupled by nose gear system problems. Therefore, when changing tire pressure, we would recommend doing so incrementally interspersed with a shimmy check. Generally, there should be no correlation between reasonable (in-range) tire pressure adjustments and shimmy. On the other hand, if shimmy is noticed, then all the nose gear system components and adjustments need to be carefully examined to discover what might be driving the shimmy. A tire pressure change which seems to excite a shimmy should be looked upon as a symptom; not a cause.

7. Takeoff & Landing

Consider treating, or partially treating, every RV-A takeoff and landing as a “soft field” operation. On takeoff, lift and hold the nose wheel/tire off the runway early in the takeoff run. On landing, keep the nose wheel/tire off the runway until the aircraft slows a little and then lower the nose wheel gently.

Goal: Keep the nose gear loads as low as practical.

Comment: If new to RVs, transition training is strongly recommended!

8. Runway Surfaces

CAREFULLY ASSESS runway and taxiway condition BEFORE use. Consider avoiding OBVIOUSLY “Very Rough” or “Very Soft” surfaces. Note: To be clear, we are not saying to avoid grass runways as there are many fine grass runways, but we are recommending that one should consider avoiding very rough or soft surfaces whether they are asphalt, dirt, concrete, grass, gravel, or whatever. Soft surfaces can become particularly treacherous when soaked. Also, sporadically holed or pitted surfaces are risky.

Comment: Anti-Splat Aero sells an add-on brace for the nose gear leg (“The Nose Job”) which is designed to keep the nose gear leg from folding under longitudinal high-load conditions by transferring the load up the gear leg. Anti-Splat also sells “The Lip Skid” designed to provide a slipping surface at the bottom of the nose gear leg. The effectiveness of these products is still open to debate. They may increase safety somewhat for rough or soft field operation, but, in our opinion, it is better to carefully assess and avoid obviously rough or soft surfaces than to depend on these products to bail you out of a potentially bad situation.

BOTTOM LINE: We hope these “Nose Gear Lessons Learned” help our fellow RV-A builders/pilots to safely build, maintain, and operate their great RV airplanes!
 
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Some builders have chosen to go with a taper pin for some improved load margin up-front, but we recommend that the taper pin installation should be viewed as an optional enhancement; not a requirement. Below is some info on taper pin installation.

IMG_3246-M.jpg


Alternate method for Nose Gear Leg retainer bolt:

Alternative: If you have not installed the engine mount or can easily remove the engine mount for working access, you can elect to replace the AN5-20A bolt with an AN386-4-13 taper pin. Many RV-A builders have done this and this alternative seems to be working fine. However, it should be noted that installing a taper pin is not a method approved by Van’s Aircraft.

There are currently two taper pin installation methods:

a. Manual Taper Pin Install (manually ream and taper the gear leg and engine mount simultaneously) by Jim Ellis and posted on Matronics as follows:

http://www.matronics.com/wiki/index.php/Nose_Gear_Strut
Note: ACS now stocks the AN386-4-13 taper pin without a separate part number, and there are other online sources for this taper pin as well.

Taper Tools:

NGT9-L.jpg


Procedure: Manually reaming the nose gear leg and engine mount combination is a three-step process which requires considerable patience and force.

(1) The nose gear leg and engine mount must be properly aligned and clamped in-place to prevent movement. Temporarily installing the AN5-20A bolt or a 5/16-inch hardware bolt (undersized) helps. Both the gear leg and the engine mount are then simultaneously (2) match-drilled and (3) reamed:

(2) Measure the diameter of the taper pin with calipers at the point where the small end will exit the engine mount. Make sure the tapered pin provides enough threads protruding for the castle nut and taper pin washer. You can set up the taper pin with the nut and washer on the threads, then line up the caliper next to the washer. For the initial match-drilling of the hole prior to reaming, use a drill bit slightly under this measurement as your initial drill size. The Matronics instructions say to use an “S” sized bit or 11/32-inch. It is always good to verify this size before you start cutting and drilling. For example, a 21/64-inch drill bit might be better.

For the initial, match-drilled hole, go slowly with the drill RPM’s and use a lot of cutting oil or Boelube frequently to get the factory gear leg and engine mount holes aligned and enlarged (matched) before you begin reaming with the tapered reamer.

(3) Put the tapered reamer into a tap handle. Using generous amounts of cutting oil, begin turning the reamer in the cutting direction only. Do the reaming slowly by hand. You will need to push hard and turn at the same time, so it helps to have another person help with the reaming. Do not turn the reamer in the non-cutting direction, or you will dull the cutting edges. Always turn in the cutting direction only. Remove the reamer frequently and clean off the cutting edges and reapply the cutting oil generously.

Once the reamer starts producing chips, make sure to frequently measure the length of the reamer or taper pin protruding from the hole. The taper pin’s grip shoulder must not protrude more than 1/16-inch beyond the engine mount, because the taper pin washer is actually a collar with a depth between 3/32 and 1/8-inch. Once the reaming process gets started, it will approach the proper taper pin depth very quickly so be observant. A few turns goes a long way to increase the cone depth of the tapered hole, so don’t get too aggressive and go too fast once you are reaming the entire length of the hole or you will overshoot and go too far.

Considerable axial pressure must be continually applied to the reamer to keep the ream process going. Above all, take it slow and do not hurt yourself!

Notes: Some builders have had difficulty keeping the reamer sharp and have resorted to purchasing an additional reamer or two to complete the process. If the reamer is not making chips and has dulled, you can try lightly running a fine sharpening stone along the cutting flute interior edges to get them sharpened up again. One or two strokes of the sharpening stone is plenty. You just want to revive the cutting edge, not take any material off in the process. Also, using a drill for the reaming step is not recommended, because it will spin too fast; quickly dulling the reamer and thus burnishing (surface-hardening) the hole. Slow, manual reaming works best with plenty of cutting oil and steady pressure being used.

There are some good pictures of the process in this thread on VAF: http://www.vansairforce.com/community/showthread.php?t=105870

b. Wire-EDM-Assisted Taper Pin Install (machine-ream the nose gear leg first and then manually ream the engine mount to match).

For those who have had difficulty with the manual reaming process or for those who feel more comfortable with professional tapering of the relatively hard nose gear leg, here is the drawing developed by Bill Pendergrass for Wire-EDM-machining (taper-reaming) of the nose gear leg hole:

Nose%20Gear%20Leg%20Taper-M.jpg


Pros: Manually reaming the engine mount to match an already-machined (tapered) nose gear leg is relatively easy. The engine mount steel is soft in comparison. Also, the nose gear leg is relatively easy to vertically align at the machine shop.

Cons: Finding a reasonable Wire EDM machining shop nearby may not be easy or even possible. The machining cost is probably at least $250 for tapering one gear leg including the set-up cost. Finding several builders to spread the set-up cost over multiple gear legs might be a good idea.
 
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So...

How do-able is the taper pin upgrade in-situ, with the engine hung?

I seem to remember there's not much room in there :eek:
 
How do-able is the taper pin upgrade in-situ, with the engine hung?

I seem to remember there's not much room in there :eek:

I did it on the airplane as a retrofit. Not easy but very possible. Search for Other threads which address some approaches to this.
 
Technically, the only approved Van’s Aircraft solution for fixing a loose nose gear leg would be to repair (weld and drill) or replace the engine mount and continue to use an AN5-20A bolt as specified. This assumes, of course, that the hole in the nose gear leg itself is not enlarged. If this hole is also enlarged or damaged, the nose gear leg would need to be replaced to remain within what is currently published by Van’s Aircraft (the original plans and drawings).

Van's doesn't generally publish approved fixes for any airframe problem.
Just because it has not been published, doesn't mean it wouldn't be considered acceptable. Because of a wide range of variables with any of teh multitudes of possible problems people can encounter, the preference is to look at each one individually.
An X or Y over sized AN bolt has been offered as a suggested fix in many instances. In fact, one of the gear legs on the company RV-7 transition trainer has an X sized bolt.

The down side is they can be extremely expensive.
 
A pic of the upgraded fork with Beringer wheel:

IMG_5777a.jpg


Also notice how the front fairing is cut high for extra ground clearance:

IMG_5789a.jpg
 
Walt, what I noticed was how your wheel pants cover that beautiful wheel. You need some clear wheel pants to show off those wheels.

Nice posts on the wheel bolt issue and clear photos to hopefully keep anyone (including me) from here on out installing things backwards. Thanks
 
nose gear grease

good write up. one thing I noticed is I seem to get better nose wheel fork grease coverage if I have the weight off the nose wheel and rotate the nose wheel side to side when applying grease at the zerk.
 
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Two weeks ago I installed a taper pin - it all went very smoothly EXCEPT for the reamer.

In short, the reamer sold by ACS was of very poor quality. It stopped making chips after getting only about 1/3rd of the way through. Dressing it allowed it to go another few turns making very fine chips, but then it would stop and need to be dressed again. A slightly more expensive tool from MSC Industrial finished the ream very quickly and is still razor sharp.

Another comment - check your taper pin washer. The comment about no more than 1/16" of an inch protruding is a guideline, not a hard and fast rule. In my case, with 1/16" of an inch protruding, the hole in the taper pin was such that it would be impossible to get the cotter pin into place. I continued the ream, slowly, until the pin extended 0.098" which allowed me to just get a cotter pin in place when the castle nut was torqued. There was still more room to go before bottoming out the taper pin washer.

Speaking of torque, there is no need to radically torque the taper pin - as has been said numerous times elsewhere, the nut is only there to retain the taper pin. Make it snug, safety it, and be done.
 
These are all very good recommendations and alternate recommendations. Thank you for pulling these all together in one concise thread. Some you may want to consider adding so that this could be considered a consolidation of the topic and one source for all information:
-1 Nose weight recommendations and limits
-Wheel upgrades to larger diameters
-Anti-splat nose brace
-Anti-splat lip skid
 
How do-able is the taper pin upgrade in-situ, with the engine hung?

I seem to remember there's not much room in there :eek:

Just pull the engine & mount - it's not hard and only took about a day. Then you can make sure everything is lined up and done properly when installing the pin.

A bonus is that you can closely inspect the engine mount and firewall. I took the opportunity to do exactly this during my condition inspection; my firewall is now spotless as well as the engine mount and the exhaust system, FWF wiring, linkages, etc. all received a very complete inspection and cleaning in the process.

The only issue I found was an adel clamp where the rubber cushion had started to crack. I replaced it.
 
Thanks so much Walt

Thanks for taking the time to compile all of this into one place. I'll be referencing your thread when I do the condition inspection on my friends RV6A.
 
Good Work.

WOW!...Nice job to you and your capable assistants Walt. Thanks for your efforts to keep us all as safe as possible.
 
These guys are just Studs. WOW Studs.

Walt Aronow (?Walt? on VAF, RV-7A), Bruce Hill (bruceh, 9A), Bill Palmer (same, 8A in-work), Bill Pendergrass (rzbill, 7A), and Alex Peterson (AlexPeterson, 6A).

I went out to the airport and performed the first test of Vans SB which is turning the aircraft in a tight radius and looking at the inside wheel spin direction. It barely was moving forward which indicates a FAIL!!! Running back out today to remove the wheel pants and check the orientation of the stop flange to see if installed correct (My only out is I am the lazy one and didnt build this thing :( But I sure do love it.

Mine is a RV9a I have the updated fork as well as the antisplataero nose job stiffiner, and beringer front wheel. << All other leg SB complied with..... just need to figure this one out.

Robert M
Olathe KS
 
PDF

Walt,
Why not offer these lesson learned suggestions as a .pdf format? That way six months from now -A drivers won't have to get to the internet and track down an old thread on a forum to review this info.

If you are concerned about changes, date and version it.

Dave A.
 
That way six months from now -A drivers won't have to get to the internet and track down an old thread on a forum to review this info.

That is why I made it a sticky------will stay at the top of the maintenance forum.
 
Thanks, Walt et.al.

Thanks to the team for assembling and posting this information. I sent a note to DR about a way to submit, vet and post such information for future reference by builders and owners. This is a very good start. A very very good start.

Vans has neither the resources or goal to do such documentation for the masses. They certainly can aid in the vetting, but liabilities may limit the ability to officially participate. This leaves the collective experience here on VAF.

The good information is heavily diluted and churned, so this type of dissemination is highly valuable.

EDIT: I put this into a pdf file, so if you want one, PM/email me and I will send it. It includes credits to authors. pictures and some formatting. It is rough, but available for your digital library. I would appreciate if an author would review it for format and suggestions.
 
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Pays to read ALL posts

Passed up this post for days now thinking it was just another rehash of the nose gear argument . It turns out that I think it is one of the most important, informative posts on the subject and that all nose draggers could learn from. Made a hard copy to put in the box with my gear equipment as a reminder and reference to improved practices. Thanks Walt, you've helped me again.;) I just wonder how many RV accidents/ incidents have been avoided due to the existence of the VAF site and it wealth of information. :D
 
B&S vs AN386

it all went very smoothly EXCEPT for the reamer.

In short, the reamer sold by ACS was of very poor quality. It stopped making chips after getting only about 1/3rd of the way through. Dressing it allowed it to go another few turns making very fine chips, but then it would stop and need to be dressed again. A slightly more expensive tool from MSC Industrial finished the ream very quickly and is still razor sharp.

Interesting, maybe that was my problem (not cutting) from the beginning since all 3 reamers I bought came from spruce. Tried dressing the reams with a stone but no luck.

While I am typing and since the conversation is about tapers and buying reams other than at spruce, I wanted to share a little more detail about the ream tapers vs AN386 tapers. This is only to head off future questions about my EDM print by dilligent persons. If you look at the spec differences between Brown and Sharpe tapers and AN386 tapers, there is a descrepancy of .001" per foot specifically on the size of pin we are using. The rest of the sizes match perfectly. To my knowledge, there is no such thing as an AN386 ream. The AN386 taper pins all (with our one exception) follow the geometry of the B&S tapers. It is my opinion that the AN386 pin drawing is "simplified" because the difference is slight and partially compensated by the taper tolerance noted.

Practically, the difference is not confidently measurable on the machined taper bore, even with common machine shop tools like a CMM because it is in the .0000x (ten thousanths of an inch) size range difference. Many factors unrelated to the part itself come into play when discerning measurements that small.

My print follows the B&S standard.
 
My RV-8A was completed in year 2000. When I was doing pre-purchase due diligence, the title search company discovered a NTSB report a few years later regarding a nose gear incident w/o prop strike. Apparently the strut was replaced with the larger diameter model according to my measurement, but alas, this was before the new fork was designed. The second owner was unaware of the incident, and he elected not to replace the fork / shorten the strut when the mandatory SB was released. I am the third owner and I am going to perform the SB, but I'm not sure what direction to go regarding the nose wheel. I'm leaning towards the Antisplat Aero solution that machines the stock wheel to accept new sealed bearings, with spacers that allow torquing the axle bolt to specs without binding the wheel - mainly because it's cheaper, and eliminates the taper bearings. I noticed that Matco offers a new axle that is similar to the Grove axle included with their wheel - which involves drilling hole to accept pins / bolts that prevent the spacers from rotating, somehow improving the torquing procedure, but retains the taper bearing and their periodic servicing requirement. The AntiSplat solution does not require the pins. Any thoughts about which way to go?
 
I would look into the Grove tubeless wheel and Desser tubeless tire. Then send the wheel in to Antisplat Aero for the bearings and spacer......

$$$ but, you will have a fine set-up and solve many nose wheel problems.

Wheel should spin free...... about 3 to 5 rotations or so. Breakout should be set to 22+ lbs. of pull with the wheel off the ground. Check it a few times after some use until it settles in.
 
Sharpening a Dull Taper Pin Reamer

Another method of dressing a dull taper pin reamer that worked for me. Using your finely calibrated eyeball as a guide, lightly press the outside flat of each flute against the flat side of a spinning Scotchbrite wheel on a bench grinder. Use a light touch, just enough to brighten the flute.
 
Grove, Berringer, or Modified Matco?

3. Nose Wheel

Replace the Van?s-supplied Matco nose wheel with an improved Grove, Berringer, or Modified Matco (Anti-Splat Wheel and Bearing Modification) wheel.

I have Matco nose wheel in my RV-6A kit under construction.

How do I decide for an upgrade between Grove, Berringer or Anti-Splat Matco?

I see Anti-Splat uses ball bearings. Grove tubeless uses ball bearings while tubed uses tapered roller bearings. Berringer I don't know.
 
Matco

Just to shed some light on this discussion, I have the vans matco nose wheel on my 7A and have not had any issues during the past 4 years that it's been flying. This 'original' equipment should serve you well if not abused.

Jim Diehl
7A
 
I have Matco nose wheel in my RV-6A kit under construction.

How do I decide for an upgrade between Grove, Berringer or Anti-Splat Matco?

I see Anti-Splat uses ball bearings. Grove tubeless uses ball bearings while tubed uses tapered roller bearings. Berringer I don't know.


The nice thing about the Anti-splat ball bearing mod is that you just tighten the axle nut and you're done, with no question as to whether you have it tightened correctly. The reduced rolling resistance hopefully reduces the odds of the nose gear tucking under. Definitely reduced maintenance.
 
The nice thing about the Anti-splat ball bearing mod is that you just tighten the axle nut and you're done, with no question as to whether you have it tightened correctly. The reduced rolling resistance hopefully reduces the odds of the nose gear tucking under. Definitely reduced maintenance.

The Matco solid axle does exact the same thing and it cost only $50 and adjustable to for a fine tune settings. Once set, the axle bolt can be torqued with no effect on the wheel.
 
The Matco solid axle does exact the same thing and it cost only $50 and adjustable to for a fine tune settings. Once set, the axle bolt can be torqued with no effect on the wheel.

The Matco axle does make it easier to put the axle bolt on without worrying about getting the exact right torque on it, but it does not decrease the rolling resistance of the tapered roller bearings with the rubber seal.
 
The Beringer is both ball bearing and tubeless.

Worth the extra upfront cost to get rid of the tube. I know of at least one builder who had to build and paint a new nose wheel pant because of a flat. That was his third flat due to nose wheel tube failure. He installed the Beringer. No problems since then. I went with the Beringer and have been happy with it. Saves a pound over Vans original set up.
 
Fore and aft vibration of the nosegear leg

Another data point in this report relesed today.

http://www.atsb.gov.au/publications/investigation_reports/2017/aair/ao-2017-001/

Interestingly, video of the nose gear collapse was available to the investigators. As usual, several factors combined to cause this incident but I found this line from the report quite interesting "In all cases, the nose gear struts and forks made contact with the ground, initiating the damage sequence. The FEA concluded that the nose gear strut had sufficient strength to perform its intended function".
 
Unsure if on this plane, the SB from Vans was done or not?
Interestingly that a RV-6A nosed over ... normaly the 7A was doing it, maybe also because of the much higher gear.
 
Oversize AN175-20A bolt solution worked for me

My RV-9A has 800 hours now, and made some noise from the front gear when using the toe bar. I found I could rock it back and forth very slightly with the weight off of it. I purchased the oversize bolt and metal lock nut, and it went back in snugly, having to turn an old nut on the bolt to seat it. After final torque with the new nut, I have no more play in the gear.
This is obviously a huge relief and thank you for the creater of this thread. It proved to be valuable information for this non builder.
 
Way too much play.... The proper amount is NONE. If the plane has 80 hours on it, the bolt is not properly installed. It may be too short. The shank must pass through the entire outer tube and be exposed by at least 1/16 inch on the nut side. The bolt has a slight taper at the start of the threads, and if that area is still in the wall of the outer tube, it will show play.

Use the next longer bolt and washers under the head and under the nut to allow full shank contact with the nut side of the hole. Do not over torque the nut. It has nothing to do with this play.
 
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Repair and improve

Is this too much play in my RV9a nose gear leg? The airplane has about 80 hours since new.
https://youtu.be/zRDVjcM0wt8

During the last annual inspection I discovered roughly the same amount of play between the nose leg and engine mount as seen in this video. Further investigation revealed the bottom hole in the engine mount was flogged out. Disappointing given that a snug NAS bolt had been installed to prevent exactly that.
A6-B905-E9-E168-4573-BA11-EBAF1-CEB5-B0-B.jpg

I think part of the problem was that I had the unfortunate experience of having two Aeroclassic tubeless tyres in a row that were out of round and exciting a lot of shimmy. Third time lucky I got a tyre that was round and the shimmy is now resolved. But I digress.

From here, installing a taper pin seemed to offer a solution to the flogged out hole. Using the procedure described on Matronics as a guide, the appropriate parts were ordered from ACS. However, it became apparent that the damage was worse than expected and the hole was too large for the taper pin.

A5-AC7548-F812-4706-B9-B5-35-A7775-A0472.png



I might have considered a new engine mount at this stage, maybe even a tail wheel conversion, but being on the other side of the world there was now no doubt the repair would involve welding.

To my great relief a master toolmaker offered to repair and improve the engine mount. As (I hope) you can see in these photos, compared to the engine mount tube alone there is now a lot more surface area for the taper pin.
75-AE9-FE0-77-C3-463-E-A400-A8-E79-AC213-AC.png


CACC95-B9-408-F-4-AAB-AAE0-BEDC1-D9-B67-E0.png


The most difficult part of all this was accepting that the engine needed to come off. It got easier after that.

Short of converting to the new nose wheel arrangement, I think my nose gear is now more robust and I don?t anticipate there being any further issues.
 
Nice

I like how that repair was done. More area to support the through bolt and a nice weld to boot. Nice job!

The danger for ?improving? an area such as this is that you could be moving the stress to another unwanted area. I?d recommend you Look at this every 50hr or maybe oil change for the next couple of years. I suspect that you will not have the wear you had before.........but since it is a change, albeit a minor one, won?t hurt to keep an eye on it.

By the way, thanks for sharing!
 
I'm going to disagree.

I'm not an engineer, but I did do the nose gear bolt replacement last year at the first sign of slight play (900 hours on turf). I had a rock solid second lease on life when I finished, but just last weekend I started hearing a new groan out of the mount when castering the nose wheel to position the plane in the hangar. I haven't checked with the wheel off the floor yet (need a helper on the tail) but I'm sure the play is back again.

I like the repair pictured above, and in my opinion the factory mount should be made this way ab initio. In fact, I find it irritating that nose wheel mounts ever left the factory the way they do. Too many have worn loose not to get out ahead of this known (or entirely foreseeable) problem.
 
anyone done the fix with an upsize -X bolt to get rid of a small wiggle on an -A model recently?
finding inconclusive information...

Is a NAS6605-26X, NAS6605-27X or NAS6605-28X the right length?

thanks for a quick confirmation!
 
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