Topic: Undercarriage for Grumman Avenger

Nooooooooooooooo.............I haven't quite finished yet....

This looks better, I think..................

Rest assured, the mounting flange at the aft side, does clear the drag link.................but only just.  



Tally Hooooooooooooooooooooooooooooo

Andy

Hi Andy, I was going through my Wildcat doc. from the fourties and found this Avenger that run out of hard top and ended up in the AA gun well...



Thought you might like the view from the AA gun as it's even more interesting 



Pretty sturdy stuff them U/C's  How's yours doing btw. 

  Johan

Johan,

Excellent pictures.................thankyou, very much..............    

I am working on the design of the tailwheel at the moment , the main undercarriage design is just about complete, I have ordered the SMC air cylinders......see pics above.........

The first part of our joint project was completed on Saturday.......................the concrete foundation slab      for Steve's new workshop where the Avenger will be built................All my muscles, still ache.............    

I'll post pictures of the tailwheel, when I have something to show you...........    

Tally Hooooooooooooooooooooooo

Andy

The first part of our joint project was completed on Saturday.......................the concrete foundation slab      for Steve's new workshop where the Avenger will be built................

Andy,

I must have missed this post but I have a nice simple question..... how big is Steve's new workshop going to be?  I've been thinking about mine, and now I'm not sure it's big enough :(


Mark.

Mark,

20' x 10', I've told him, it won't be big enough.....................but, he has got his garage also.......        

4 Cu/M of concrete, I've only just recovered....................We did think about doing a 'shed' build thread ........      

Tally Hooooooooooooooooooooooooooooo

Andy

20' x 10', I've told him, it won't be big enough.....................but, he has got his garage also.......        

20' x 10' that's as big as my garage   now I'm positive my 12' x 8' will be too small :( 

It looks like most of the power tools will have to stay in the garage (if I can find 'my end' of the garage )


Mark.

20' x 10' that's as big as my garage   now I'm positive my 12' x 8' will be too small :( 

It looks like most of the power tools will have to stay in the garage (if I can find 'my end' of the garage )


Mark.

It is...........................My shed is 16' x 10' and that is too small, but I couldn't have it any bigger, without even more major groundwork, so I had to be satisfied with it as it is.

Design of the tailwheel is progressing nicely, but I need some F/S pictures. I need to eyeball Steve's new book.........    

T H

Andy

Hi Andy,

I know you love re-inventing the wheel but have you seen this little lot?
http://www.sierragiant.com/prod26.html

I see Darrell also offers plans for these retracts, too.

TTFN,
Neil

Neil,  thats the reason this build is now on,I wanted to build this model a long time ago but the retracts are pretty expensive from Darryl, $800 plus air kit and shipping, vat etc stopped the project, I'm not saying they are overpriced as there is a lot of work goes into them (right Andy ).

Then along came Andy who wanted to have a go at something like this, so we get cheaper and probably IMHO better retracts, plus the satisfaction of the design, build process.

Steve

Hi Andy,

I know you love re-inventing the wheel but have you seen this little lot?
http://www.sierragiant.com/prod26.html

I see Darrell also offers plans for these retracts, too.

TTFN,
Neil

Thanks for the heads up, Neil...................we do know about them..............

We have dismissed them on the grounds, that they are very expensive and not very close to scale, the main legs, lack the folding side strut and the tailwheel isn't much like the full size.

The plan is that we are going to 'blow yer socks off'................ note, I said plan, reality is often, somewhat different.       

Keep watching buddy......................

Tally Hoooooooooooooooooooooooooooo

Andy

Phew.............................we both said the same thing..........lucky or what............        

Phew.............................we both said the same thing..........lucky or what............        

Not luck at all 

I see Darrell also offers plans for these retracts, too.

Neil,

Darrell sends you straight to Charlie for the plans, (they're for the aircraft not the gear btw)  which is why I'm now waiting for 2 large boxes from him ::cc ::cc  (it's only taken 11 months to get this far )


Mark.

which is why I'm now waiting for 2 large boxes from him ::cc ::cc  (it's only taken 11 months to get this far )


Mark.

Nice one mate 

Steve

Charlie shipped my boxes yesterday   he says 7-10 days.

He's sent me piccies of the boxes with my name on them ::cc and a couple of the contents.  I can't post them here though, as the internet cafe won't let me d/l them


Mark.

Just a quick update................

The retracting tailwheel design is nearly complete..........I expect to have the 3D model drawings of it finished in a day or two..........

Keep watching.............

Tally Hooooooooooooooooooooo

Andy

Dear Tiger
Your current avatar is the best one so far
Or should I retract that comment.

Regards Phil G.
PS. Keep up the good work.

Your current avatar is the best one so far

Yep, I think it's pretty good too...................Many thanks to Steve for it.......

Tally Hooooooooooooooooo

Andy

OK guys this is the first stab at the tailwheel design............

Let me know what you think, please.....  





To give an idea of scale the tailwheel is 1 - 3/4" dia the mounting angles are 1/2" x 1/2" the cylinder is 10mm bore and gives a 10 lb  pull at 100 psi.............sorry that we have imperial and metric units, but that's the way life is...........  

The lower part, the bit that is visible, below the fuselage, is about as close to scale as I can manage and still keep it practical to manufacture.

Tally Hoooooooooooooooooooooo

Andy

Andy, how do you know if all the distances and angles of the various pivots are correct so that when the piston pulls it up, the leg will actually rotate and move the correct amounts, and none of all those connecting pieces will try and fight one another due to mismatched lengths when it all starts to rotate?  Can the CAD be told which points are pivots and fixed to the frame and which points are pivots but can move position so that the CAD can simulate a retraction?

Hi Andy, watching with interest. I've only just found this thread. If you need "bits" let me know. I'll soon be oredering some ally angle that could be useful for you 

To give an idea of scale the tailwheel is 1 - 3/4" dia the mounting angles are 1/2" x 1/2" the cylinder is 10mm bore and gives a 10 lb  pull at 100 psi.............sorry that we have imperial and metric units, but that's the way life is...........  

The lower part, the bit that is visible, below the fuselage, is about as close to scale as I can manage and still keep it practical to manufacture.

Tally Hoooooooooooooooooooooo

Andy
[/quote]

Andy I need a lesson....
 You once told me the formula for working out psi/bore dia = pressure, but what confused me was the use of imperial and metric.


Well, here's my way, and I've been head scratching to see where I've gone wrong.

Your Bore is 10mm and you've got 100 PSI

Therefore the Area is pie(3.14) x r x r (Am I right so far?) = 78.55 mm sq

To convert that to imperial divide by 642.2 = .12 square inch

Multiply that by your PSI 0f 100 = 12 pounds of pushy things.

  Colin (probably applying too much logic)

Harry,

I am a mechanical design engineer and have been for about 40 years. There are ways of 'laying out' these mechanisms to ensure that the system works as it should. The fact that I have used CAD in this instance is of no consequence, the job could of been done on a drawing board with paper and pencil. CAD, allows you to be extremely accurate, 12 decimal places if required  3D CAD, presents the finished article in a way that 'non-engineers' ( some one like Christine  ) can appreciate. The prime requirement for this sort of job, is a good understanding of geometry. Some 3D CAD systems do allow the designer, the luxury of 'moving' 3D models, I have worked on some over the years, unfortunately the system I have now does not.

However, I have 100% confidence that this mechanism will operate exactly as it should.....    

Colin,

Thank you for the offer, much appreciated, if we need anything, I'll give you a shout. I do have some angle the correct size, but I haven't machined any of it yet, so I don't know what it's like..............you know what I mean.    

Thanks again........

Tally Hooooooooooooooooooo

Andy

Colin,

You a correct to a point..............

What you have forgotten, is to subtract the cross sectional area of the piston rod............in this particular case.

The cylinder is pulling not pushing.......................       if it was pushing you would indeed, be correct.......    

Tally Hooooooooooooooooooooooooooooo

Andy

So from that I should be able to work out what size piston rod you're using.... more head scratching 

4mm.................Std SMC double acting cylinder.

The lower part, the bit that is visible, below the fuselage, is about as close to scale as I can manage and still keep it practical to manufacture.

Tally Hoooooooooooooooooooooo

Andy

Looks nice Andy, I was just looking at the tailwheel yesterday, welded tubes, just like your model

Is the shock strut fuctional?


Mark.

Looks nice Andy, I was just looking at the tailwheel yesterday, welded tubes, just like your model

Is the shock strut fuctional?


Mark.

It can be, the design allows for it. We thought to start with, I will make it a solid rod, we will then build the model. See how it behaves, maybe, sit the tailwheel on some weigh scales, then determine if it is worthwhile to make a spring/damper unit. It is possible to calculate what the expected weight on the tail wheel will be......................but, what, will be the final weight of the model?...........

Bert's method seems more practical in this case.............at least the provision is there.

All the tubes that are used in the design are from the range supplied by Tony Clark, mostly stainless, but the 10 mm dia 'main' pivot tubes and steering post are carbon steel, the whole assembly will be silver soldered together..............I am looking forward to designing the jig to hold all the parts in place while it's being soldered. The upper parts, non visible will be ally...............

I tried to keep the visible bits as close to the full size design as practical. It's tried and tested .......see   

Tally Hoooooooooooooooooooo

Andy

Wow, Great job. Look very similar. Glad I could be of help.

Darrell Tenny
Sierra Giant

Guys,

Just in case you think I've dropped dead, unlucky, I'm still here........

No further progress to report, Steve and I have a couple of other projects near completion and we will finish these before we start the Avenger.

Designs are just about finalised, but I expect a few things will change once I start the machining, they usually do........

I will post, when something has happened.

Wow, Great job. Look very similar. Glad I could be of help.

Darrell Tenny
Sierra Giant

Darrell..............Thanks for the compliment, I am pleased that you are watching.

Until later guys........

Tally Hooooooooooooooooooooooo 

Andy

Designs are just about finalised, but I expect a few things will change once I start the machining, they usually do........


Tally Hooooooooooooooooooooooo 

Andy

Proper engineering then! 

Dearest Lord Tiger of Tuffley...

Proper job mate!!!

Thought you'd like to see a picture of the U/c for the Helldiver we talked about....



Whilst not the same, there is certainly some shared DNA between the designs isn't there??

and as for the comment about buying v making, well, i will be buying mine from Darrell at Sierra, Why?? Well every u/c manufacturer says they make a scale set for the 100" bates helldiver....but 100% are 0% scale!! and:
a. I don't have a lathe
b. I don't have a mill
c. I don't have the skill (I am only very capable with a ball peen hammer  ::cc ::cc)

Keep up the good work mate.

Tallyski Hoski

Neil

I am only very capable with a ball peen hammer  ::cc ::cc)

Keep up the good work mate.

Tallyski Hoski

Neil

I wouldn't go that far either matey, 

Hows the Storch coming on ?

Steve

I wouldn't go that far either matey, 

Hows the Storch coming on ?

Steve

aaaaaaaaaaaaaaaaaaagggggghhhhh

aaaaaaaaaaaaaaaaaaagggggghhhhh

Good as that eh!!!  :laugh:

Hi Guys, are you flying seaplanes instead of keeping this very interesting thread going 

  Johan

Sorry Johan, we have both been busy, but we hope to make a start soon. 

Steve

Now whom did I meet at Cosford that was pondering over a new kit...   

Guilty as charged