Avid Flyer Mk IV Major Change and Upgrade


31 posts in this topic

Posted (edited)

Well after my illustrious gear fail landing last October, I have gathered the parts and will be getting her ready for flight in mid to late Feb.  I pulled my 582 (using a Harbor Freight hydraulic table, which was surprisingly easy.) I packed it up in a big plastic tub sold at Walmart, using about 5 pillows as recommended by 'Rick".

I shipped it to "Rotax Rick" Ron Davis, and he swapped parts and is sending back (4 weeks later) a zero time 91 HP 670 engine with my C box. I will also install a Warp Drive 3-blade 72" Prop with Standard blades, nickel leading edges and HPL hub, ground adjustable, and a new set of wide Lowell Fitt gear with my old 8.00 x 6 wheels and brakes to round out the major items.

I will keep you all informed of how it goes, I will drop back to Phase 1 for 5 hours, and take careful notes.

I am now based at Parowan, UT, so that 6000 feet will make the 91 HP mighty welcome.

 

670.jpg

Gear 338Ssmall.jpg

Edited by nlappos
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Posted

I’ll be watching your 670 testing closely!! 

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Posted

I've never known of anyone still regularly flying one a year later.  

I hope you have better luck.

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Posted

Great! I too will be pulling for you! What shape/type of exhaust system will you be running? That's the main thing from keeping me from putting a 670 in my MKIV.  

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Posted (edited)

I have an exhaust modified from my 582 system by Mike Hair. I'll let you know here how it fits. I think it looks generally like this for an upside down Avid Mk IV

exhaust.jpg

Edited by nlappos
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Posted

The mass moment of inertia on the 72” square tipped Warp probably exceeds the capacity of the C gearbox (6000 kg-cm^2). Most opt for the taper tip if they're using a three blade Warp. 

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Posted

Av8r_Sed,

I am checking with the Warp Drive folks. Some literature says ok, some says not (70" max for 3 blades). Thanks for the heads up.

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Posted (edited)

I keep repeating this, but Daryl told me that I would probably get same TO and faster cruise with more static pitch on 68" 3-blade tapered than with 72" for my Subaru engine.  EDMO

Edited by EDMO

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Posted

Av8r_Sed,

I am checking with the Warp Drive folks. Some literature says ok, some says not (70" max for 3 blades). Thanks for the heads up.

Warp Drive wants to sell you a prop.  They are not the people to check on this with. 

If you don't believe us, call LEAF, Lockwood or CPS to get accurate information on your Rotax gearbox.

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Posted (edited)

I have always had a good experience dealing with Darrel at Warp Drive.  I don't doubt that he would try to convince me that a Warp drive is better than an IVO, but I think I can believe him if he says : this Warp drive prop should work in your application.   I have a 70" or 71" LH taper tip Warp hanging on the wall at home.  Has new blades, used hub, SS inlaid leading edge protection.  Also have a 70" square tip LH used but good shape.  I'm not around there right now, but if it came down to it, I could get my son to ship one.  PM me or give a call  218- seven five zero- 38fiftyone.  JImChuk   PS  spinners for both of them also......

PS PS  just ran across  a picture of the square tip, and it's a 68" diameter.  

Edited by 1avidflyer

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Posted

I don't know if they still will shorten blades for you, or exchange blades with you, or what the cost, but believe they have worked with buyers before to give them satisfaction.  EDMO

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Posted

Av8r_Sed,

I am checking with the Warp Drive folks. Some literature says ok, some says not (70" max for 3 blades). Thanks for the heads up.

Warp Drive wants to sell you a prop.  They are not the people to check on this with. 

If you don't believe us, call LEAF, Lockwood or CPS to get accurate information on your Rotax gearbox.

Agree.  Bad prop for the C and when used on the 912 they will tear up the sprag clutch too.  They sure are easy to repair and maintain though.  Lot's of thrust too.  Good prop on a belt drive PSRU. 

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Posted

After the head's up (Thanks AV8r_Sed!) I did some homework. The polar moment of the Warp Drive 3 bladed at 72" is slightly (10%) above 6000 kgcm2, so I sent it back for cutting to 70" and tapering. Won't slow down my refit.

This is a pretty good group.

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Posted

Ok lined up all the major items for the refit of my Avid. New Rotax 670, new Warp Drive prop (cut and tapered), new Fitt Cabane Gear, and new matched exhaust system. Tomorrow starts the wrench turning!

IMG_0012.jpg

IMG_0013.jpg

IMG_0014.jpg

IMG_0021.jpg

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Posted

Nick,  Are you going to use those stiff springs?  EDMO

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Posted

nlappos,

I hope you realize that is not the correct manifold for your 670. If your plane is a Kitfox you will need the shortest version of the Rave engine manifold to keep the elbow from interfering with the cowling.

 

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Posted

Sorry nlappos, I see your picture is prior to modification of the exhaust and your plane is an avid. Please disregard my prior comment.

PS Mike developed the 582 pipe modification on my 670 engine

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Posted

FoxDB

Sharp eyes! That’s the old 582 Y pipe I was matching for size. The short fat 670 Y pipe is coming from EBay soon.

Any thoughts on EGT?

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Posted

Nick,  Are you going to use those stiff springs?  EDMO

What would you recommend instead, EDMO?

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Posted (edited)

Nick,  Are you going to use those stiff springs?  EDMO

What would you recommend instead, EDMO?

Leni had a Snomobile spring substitute that gives less stiffness and more travel before the spring coils bottom out on each other.   The earlier post made about the springs you have described this problem which can bend your longerons.   I think the Snogo springs are 325 lbs / inch compression.  I bought one before he said that I might be better off with a 190 or 220 for my nosegear.  Not trying to sell it to you. 

I think they are Honda, and I copied the chart he posted.  If you cant get info from him, then TJay or others may have bought them, or I can look at my unopened package and maybe get the numbers and address for you.   I don't know where the original posts are about this, or where the chart is.  Others know more than I do about this.  Maybe you can search for the posts?  I've got Grove gear, so just reading about these.  I am unfamiliar with the Fitt gears, so just wanted you to know there may be better options for them.  EDMO 

Edited by EDMO

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Posted

Ed,

I will check the spring rate on the ones I have as a start. Meanwhile, any advice from the Guys Who Have Already Been There?

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Posted (edited)

Ed,

I will check the spring rate on the ones I have as a start. Meanwhile, any advice from the Guys Who Have Already Been There?

Here is link to spring chart that Leni posted. 

Posted 12 Jun 2017 · Report post

Here is a chart for various snowmachine springs that can be used for those of us making or modifying a spring type gear.

 

Snowmobile_Rear_Suspension_-_Front_Arm_Springs.pdf

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Ed,

I will check the spring rate on the ones I have as a start. Meanwhile, any advice from the Guys Who Have Already Been There?

Here is one copy of the chart Akflyer posted.  I think the thread may be "Bush gear failures"?   I cant find "325" on there, so maybe he gave me a number to order it from another chart?   EDMO

For those of you that have been having issues opening it up ad a PDF here are a few more options for you.

 

:BC:

 

Snowmobile_Rear_Suspension_-_Front_Arm_Springs.docx

Snowmobile_Rear_Suspension_-_Front_Arm_Springs.jpg


Don't expect me to be politically correct....
#1 snake oil sales man since 1-22-09
Leonard Perry

Edited by EDMO

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Posted

Lots of info on this.  The gear geometry is kind of hosed up and with those spring you only get around 1.8" of travel before everything goes metal to metal and you bend your gear or your bird.  LOTS of documented cases on this.

Bob McCaa (I think) posted a well written word doc on his "research" and figuring out what helps the design the most.  Seems that #1 is to lower the attach point for the strut from the top of the axle tube to the end of the axle tube like the cub gear is.  He made a pretty nice mod for that.  #2 would be to lower the attach point on the vee 2-3 inches so you don't have a straight pull on the cabane strut tubes. 

#3 is to lengthen the slots and change out to the other springs that give you more travel before things go metal to metal.

My new gear design takes all this into consideration and fixes the issues that other gears of this type have had.  Ease of manufacturing means shit when you are destroying peoples airplanes and breaking their backs.  My gear wont be on the market till I beat the ever loving crap out of it and prove to myself that true "bush" or off airport work is not going to fold them or the plane up the first time you hit a good bump or drop it in from a couple feet.

:BC:

 

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Posted (edited)

I did an analysis of the Fitt Cabane gear that I have and the numbers all look good, as does the sizing of the coil spring. Let me post them for you all to shoot holes in them (and the way I analyzed it).

 

Fitt Gear.jpg

Edited by nlappos
analysis redone more data

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Posted

Beef up the sides of the fuse and seat truss.  computer numbers are always better than flight reports, pics of bent fuselages and pireps hahahahaha.

:BC:

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