Hornsb-Akroyd Crawler Tractor build

[10KPete]

Gail, I went back through this thread but didn't find the answer; how will you steer this thing? The two sides seem to be  locked together at the double 16 tooth axle.

Pete

[GailinNM]

Pete,
I explained it some back on post #64 but it will be more clear if I elaborate here now that more parts have been made and more drawings posted.
First off in the latest drawing I show the 64 tooth gear attached to the rear axle.  That should have been labeled as "Rear Axle ASSEMBLY". In post 64 I had in exploded view of the rear axle but to make things easier I am posting it again now.


The 64 tooth gear and associated clutch plate have not yet been made so there are no photos of it. At the time I was not sure that I could get every thing else around the gear and that I might have to drop  down to a 60 tooth gear. Now I know that the 64 tooth gear will fit.

The As you noted the two 64 tooth gears are coupled to each other with the 16 tooth gear pair that locked to each other.  The 64 tooth gears are free wheeling in bearings on the axle and have a dog clutch face as a part of them. The dog is double sided and is keyed to the axle.  When slide one way it engages the 64T gear through the clutch face to drive the axle. When in the middle the axle is free wheeling and drag will cause a gradual turn as the other axle will be under power, and when slid all the way away from the gear the other side of the dog engages the brake facing which is bolted to the frame and locks the track to the frame for a full skid turn.  The left and right dogs are driven through yokes by a servo which allows both axles to be powered when it is in the center position and goes through the above routing for one axle or the other as it if moved away from center.

I used two  64T gears so I could put the inner axle bearings between them on a bracketIt seemed to be the easiest way to get the inner bearings mounted so the axles were independent.

I will probably get to the 64 tooth gears and clutch plate in ablut two beks when all the other gears are finalized.  I want to cut all the gears at once as I need assistance to mount the indexing head on the mill as I no longer can do it by myself. It only weighs about 40 pounds -- but getting old sucks.
 Hope this clears it up for you (and quite possibly others).
Gail in NM

[10KPete]

Got it!  Thanks Gail. 

Pete

[Roger B]

I'm still following along and enjoying the build     

I think that you said somewhere that you had made some O gauge locos with hit and miss engines. Are there any details available?

[GailinNM]

Thanks for following along Roger.  Not much of note accomplished on the crawler for the last few days.  Some more CAD detailing and metal sawed and squared up for chassis parts.  My band saw has  has a few issues so I took 1/2 a day off to correct them. And since we have had n ice weather I worked outside to prep the flower beds for spring.

Roger, your memory is fairly good, but the locomotives were Gauge 1 instead of Gauge 0.  For those not familiar with the gauges, Gauge 1 is 1-3/4 inches (45mm) bet/ween the rails and Gauge 0 is 1-1/4 inches between the rails. I have built ten locomotives using this engine design in Gauge 1.  I wont clutter this thread up wit a lot of photos of them, but since it is the same engine design I will show a little bit.
Here is a Woolwich Arsenal locomotive and was the first IC powered locomotive produced. I built 6 of these with minor variants plus 2 prototypes.

ANd here is a video of one of the prototypes running at idle on a track so you can hear what the crawler should sound like.
<a href="https://www.youtube.com/watch?v=a-csJ3As7dc" target="_blank">http://www.youtube.com/watch?v=a-csJ3As7dc</a>
And finally a video of the last IC locomotive built with this engine.  It is a Baldwin Mechanical as used during WW1 as a trench locomotive for moving goods and personnel to and from the front lines, mostly in France.
<a href="https://www.youtube.com/watch?v=xXnWSJOSuE0" target="_blank">http://www.youtube.com/watch?v=xXnWSJOSuE0</a>
Gail in NM

[Roger B]

Thank you Gail, very nice models   

The Ffestiniog Railway in North Wales has a much modified version of the Baldwin fitted with a diesel engine and an additional pair of carrying wheels at the front.

I was confused remembering the gauge as I have models in both. In the picture the high level is 32mm gauge and the low level 45mm.

Is that your outdoor line? It looks to be dual gauge, what is the second gauge 2", 2.5" or the strange 'American Standard' 2 1/8" ?

[GailinNM]

Thanks Roger.  Yes, the track is dual gauge for one loop. 45mm gauge and 2-1/2 inch galugle.  The track belongs to Jim, my building friend, in Utah, about 600 miles from me.  Each loop is 250 foot long, a scale mile in 1:20..7 scale which is popular for live steamers in the Rocky Mountain reagon as we have numerous 3 foot narrow gauge mining railways. 

Sorry for the delay in updating this thread.  Not a lot of progress on the crawler but I have not been idle.  Back in the beginning of this trhread there was a photo of the band saw setup sawing strips of 1/2 inch plate for the trread plates.  I was sawing through the 10 inch section of the plate.  When cleaning up the strips to width I noticed the the cut had a bow in it of about 0.-25 inch.  This  is normally an indication of insufficient tension in the blade. So I set up my shop built tension gauge.  Sure enough my calibrated thumb that I had been using to set tension had gotten out of calibration. By about 2:1.  Blade tension should have been 15K to 20K PSI.  I measured 8K.   While I was at it I decided to change the tires on the saw blade wheels as the old ones were getting really bad.  Went with polyurethane tires. Because of the odd size of this saw they were  cheaper than the old rubber tires.  Took a few days to get them but they work very well.

So with that and a few other shop and household chores out of the way it is back to the crawler.

Nest up was the 64 tooth gear and clutch drive plates for the rear axles.  They started off life as some 1144 steel barstock 1-3/8 diameter.  Faced the end and turned down an 1/8 long section to 1 inch diameter  for the clutch plate. Then parted off to a little over 1/5 inch thick.  I know there is more overhang from the chuck than is desirable, but with sharp toos and slow feeds I had no problems. Besides  none of these dimensions are very critical.
Gail in NM

[GailinNM]

The blanks were held in a 1 inch collet and faced off to 0.250 inch long. This dimension is some what critical as a bearing is going to be installed in each side with a spacer in between the inner races. If the dimension is held it makes it easy to get the spacer length right so there is no axial pressure on the bearings.



Then the blanks were center drilled, drilled and reamed 3/8 inch diameter for the bearings.



Gail in NM

[GailinNM]

The blanks were moved over to a vertical 5c collet on the milling machine and the 12 holes that engage the dogs for the clutch were put in with a center cutting 5/32 4 flute end mill going to a 0.140 depth.  The collet may look a little funny as it is one of my standard ones that I made up from a 5c clutch dollet blank that has both 1=3/4 and 1-3/8 pockets in it. 
Gail in NM

[GailinNM]

The blanks were then mounted on a mandrel held in a dividing head on the CNC mill to cut the gear teeth. The dividing head is an ancient Ellis head that I put a 5C collet closer on and am driving with a stepping  motor being driven with a Sherline rotary table controller.  My CNC controller does not have a 4th axis but provides an Index Out pulse on command and then waits for and Index back pulse from the Sherline controller when the indexing is complete before continuing.



And for those of you who nust have some action here is a 40 second video clip of the gear cutting. Two passes are made for each tooth.
Gail in NM

<a href="https://www.youtube.com/watch?v=MkYW26nGCNI" target="_blank">http://www.youtube.com/watch?v=MkYW26nGCNI</a>

[zeeprogrammer]

Gosh. Even with close-up shots the parts look fabulous.

Outdoor track...envy.

[GailinNM]

Thanks Zee.  I am not much for running trains, I mostlly like to build things.  My track is a pile of LGB track that I set up for testing before hauling my toys off to steamups on other peoples tracks.

Finally here are the finished parts ready for assembly.
Gail in NM

[90LX_Notch]

Gail I always enjoy your builds and have been silently following along.  This is a really neat project.

-Bob

[GailinNM]

Thanks Bob. BTW I really enjoyed your Ultra Tiny project.  I built a 1/16 X 1/16 bore-stroke years ago so really appreciate what you accomplished. I got the  ports a little off so it was harder to start than yours.  I put a microphone near the exhaust on it and fed a freq counter and it measured about 40K RPM at 15 PSI as I recall.

I ran into a minor problem with the crawler.   The just completed 64 tooth gear/cutch disk is supported by two FR168 ball bearings with a spacer in between them to take the axial pressure on the inner races when mounted.
     
I made up the spacers to ny drawing and installed the two bearings and spacer in the gear and assembled to the rler axle assembly.  The gear did not turn freely.  Disassembled the axle assembly and measured across the bearing faces.  It measured about 0.009 more than it should.  Removed the spacer and it still measured the same so it must be the flange thickness on the bearing.  China bearings so any thing is possible.  Measured 0.e036 thickness. Off to the internet for specifications.  Found two different specifications.  One for 0.023 amd one for 0.036 thickness, with most manufacturers not even bothering to dimension it.  SKF and other brand names showed 0.0336 and since that agreed wit what I had measured on my bearings I decided that it must be right.

So where had "I" screwed up.  Went to my CAD model of the bearing  that I had made years ago and I had drawn the flange thickness as 1/32 (0.0313). Why? Well probably because I normally keep the snap setting on the CAD lat 1/64 inch and assumed the thickness was 1/32. This was the first time that it had bit me.

After changing the /model of the bearing I had two choices.   I could counter bore the 64 tooth gear by 0.004 on each side or I could change the spacer thickness.  Since I had allowed an extra 0.05 on the axle length to allow for tolerance build up from machining and plate thicknesses I  went with changing t spacer length. none of the mating parts would be affected.

New spacers made, installed and everything is fine.
Gail in NM

[Tennessee Whiskey]

You can pull their leg, but not mine; Coot figured that out didn't he? I once heard " The difference between good and great is how well you cover the mistake " Think you're well on the way to past great.

Cletus