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Modified MD 45-MD55


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#1 camdigger ONLINE  

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Posted May 27, 2015 - 12:25 PM

I have always been fascinated by crawlers, especially dozers. I have had numerous opportunities over the years to sit on some and even to chase some around pushing a bit of dirt. I've sat on assorted cat machines including D3C, D4H, D5H, D6C, D6H, D6R, D6T, D7G, D7H, D8H, D8K, and D8Ns, a couple JD machines JD 450, JD 850C, Komatsu D65, D65EX,and even an old Deutz of unknown model +/- 200 HP.

I first started seeing the Struck ads in the first Pop Sci and Mech Ill magazines I bought about the time the MD45-55 were still current models. I sent for some info then and again later when the Magnatrac 3000's were new. In that time period even the kits were about the same as my folks paid for the family ride - a bit out of my price range as a teen, so that dream was quashed.

A few decades later, when we were joining the information age of the interweb, I found the Struck website. I pounded through all the pages until I found the Tech section. At that time, they had uploaded PDFs of the plans for the MD 45-55 models. I downloaded the plans and started to dream again. I was especially enthused when I found that the plans Struck had posted included dimensioned drawings.

In the intervening years, I had managed to out together a reasonably well equipped welding/machining shop. Among the various and assorted projects, I had built a few things like the Cadtrac 1500 for Cadplans and some other implements.

Upon review of the plans, I recognized several elements I'd seen in other applications, especially Ag equipment and eventually convinced myself it would be possible to build a mini dozer in my own shop. The only stumbling block was the track system, but by that time, I'd seen some other systems on heavy equipment like Nodwells and Sno Cats that were not based on track chain. Struck themselves even had a track system based on belts for one of their early offerings.
So the story begins. First the side plates.
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I didn't have a source for the identical bearings Struck used, but I did have a good source for flange mount bearings and keyed shafting. So I marked out and cut the shaft hole locations with bolt patterns to match the flange bearings I could find locally.
After the side plates came the bottom plate and rear axle mounts.
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#2 camdigger ONLINE  

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Posted May 27, 2015 - 12:37 PM

AS per Struck, I made the front idlers to rotate independently on a "fixed" front axle. I put the fixed thing in quotations because although it does not rotate with the front idler, the front axle does slide front to back enough to tension the tracks. The rear idlers have the "bull gear" sprocket of the final drive firmly welded to the final drive hub, which in turn, drive the individual tracks. The tracks have to be independent so that they can turn at different speeds to turn the crawler. With a careful selection of sealed ball bearings and hub stock, I found a combination that with a little lathe work and a dose of 7018 made up the hubs.

A front idler
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Rear drive sprocket and hub
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Some process pics

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Edited by camdigger, May 27, 2015 - 12:48 PM.

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#3 camdigger ONLINE  

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Posted May 27, 2015 - 12:44 PM

The Struck minidozers from the MD45 up to the Magnatrac series and the RS 100 and RS196K, use a belt drive transmission design with counter rotating shafts  The earlier machines use a hex profile belt wrapped around the driven pulleys to drive the counter rotating shafts which are then clutched to the final drive with vee belt clutches.  The RS units still have the final drive vee belt clutches, but the counter rotating shafts are driven by a roller chain.  I managed to find weld on pulleys on sale and had the means to make my own custom weld on hubs for the transmission layout.  I even made my own flat faced idler pulleys for the vee belt clutches. 

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Edited by camdigger, May 27, 2015 - 12:46 PM.

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#4 camdigger ONLINE  

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Posted May 27, 2015 - 01:06 PM

So next would be assembly of the transmission....  Far easier said than done, but it did get done....

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Sorry, no real good step by step documentation of the tranny assembly.  I was too busy trying our every bad word in my extensive vocabulary getting all the shafts and belts in the right spots.  As soon as the tranny shafts were assembled, I put on the axles, hubs, and wheels.  Note the MSFH (medium sized f&*^% hammer) still strategically close to hand after assembling the tranny.

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Now nearing the home stretch, I tried to mount the engine - DISASTER!  I had hoped to use the 13 HP Honda knockoff I'd bought on sale for this crawler. Turns out, the body was all of 1" too narrow....  I had to go down to the 6.5 HP Chicom motor to get one to fit.  That means less power, less chance of addition of dozer hydraulics in the future, and no electric start.... sigh.

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#5 camdigger ONLINE  

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Posted May 27, 2015 - 01:25 PM

As the astute observer will already know, I did not opt for a steel track design, but chose to use a belt design instead.  A sympathetic neighbor friend donated me enough antique 6" flat belt to build several mini dozers.  I decided to make up a grouser/guide system using internal guides for track alignment bent up from flat bar using a cheapie knockoff of a Hossfeld bender.  This shows the progression of the guide bars from flat stock to guide...

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I made up a drilling jig and drilled all the holes for the two track belts using a screw tip power drill bit for wood.  It worked better on the machine belting than anything else I tried.

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Of course after all the holes were drilled and the parts drilled and bent, the grouser bars and track guides were installed on the track belts.

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After the belts were assembled, they were installed over the drive and idler wheels on the machine.

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The last item was to install and tension the final drive chain and do the final tensioning of the tracks.

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Almost forgot the footrests.  Cut out of 10 gauge with plasma torch guided by a wooden pattern, bent up in a pressbrake and welded in place for the final touch to date.

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#6 camdigger ONLINE  

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Posted May 27, 2015 - 01:28 PM

So a once over for final adjustments, fill oil and fuel, crossed fingers, pull the starting rope a few times, and... IT LIVES!

 

https://www.youtube....A&feature=email

 

Some comments.... 

The machine moves faster than the Struck models because the wheels are larger than the Struck sprockets.  Makes it harder to control, but might make a better snow plowing machine.

Belt clutches are a bit grabby.  Hopefully, they will wear in a bit and I will eventually get the hang of the little critter.

The tracks have too much grip sideways.  The tracks tend to come off on turns.  The hex head bolts should be replaced with countersunk heads like plow bolts.

The ride is surprisingly rough.  I think the grousers are too far apart. I should really take the tracks off and add a grouser between each existing set.

 

Still to come someday....

Raised dash like the RS models.

Hood

Grill

Dozer and linkage

 

I have an old pressure tank cut up for the mold board of a dozer blade, but need the framework and cutting edge material.

 

So many projects, so little time.  The project got mothballed long term when I cannibalized the motor from it to get my logsplitter (also shop made from scratch) running after I broke the pull rope on it trying to start it in the spring after a lengthy winter rest. 


Edited by camdigger, May 27, 2015 - 01:41 PM.

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#7 boyscout862 ONLINE  

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Posted May 27, 2015 - 02:09 PM

A very nice job and presentation. Good Luck, Rick


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#8 Bmerf ONLINE  

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Posted May 27, 2015 - 02:29 PM

Awesome :worshippy1:

 

Just a suggestion; Would a smaller (or is it larger?) pulley on the engine slow the whole transmission down, making it a bid more manageable?  

 

 Great write up. I can't wait to see more.


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#9 superspeedex OFFLINE  

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Posted May 27, 2015 - 02:31 PM

Nice


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#10 Bruce Dorsi OFFLINE  

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Posted May 27, 2015 - 03:18 PM

Very interesting!  :thumbs:

 

Thanks for posting here!


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#11 Chopperhed OFFLINE  

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Posted May 27, 2015 - 06:26 PM

Awesome :worshippy1:

 

Just a suggestion; Would a smaller (or is it larger?) pulley on the engine slow the whole transmission down, making it a bid more manageable?  

 

 Great write up. I can't wait to see more.

A smaller one on the engine would do it, or a larger one on the driven shaft


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#12 camdigger ONLINE  

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Posted May 27, 2015 - 08:26 PM

Awesome :worshippy1:

 

Just a suggestion; Would a smaller (or is it larger?) pulley on the engine slow the whole transmission down, making it a bid more manageable?  

 

 Great write up. I can't wait to see more.

 

Thanks for the compliments!

 

A larger pulley on the engine would make the machine faster with less tractive force.  Smaller engine pulley would make the machine slower with more tractive force.

 

The issue becomes one of what will work with the Hex section drive belt.  IIRC, the belt is a AA section.  Being a hexagonal section belt, it is less than half as flexible as a standard VEE belt of the same nominal size that has a 4 sided cross section.  At some point, the turn around the pulley becomes too sharp, and belt life suffers as does power transmission efficiency as a lot of effort is put into flexing the relatively stiff drive belt..  A belt supply catalog's engineering section might have data on minimum pulley size.   Boston Gear and Martin Gear both come to mind re Engineering sections in catalogs.  Gates or Goodyear belts might have them too.

 

Belt flexibility issues aside, a smaller drive pulley is more practical than larger driven pulleys for 3 reasons.

1.) there are two driven pulleys and a single drive pulley to be replaced.

2.)  there are clearance issues around the driven pulleys already

3.) because the driving pulley is smaller, a given size change, say 1/2" smaller will make a bigger change in the smaller pulley as a percentage of circumference than the larger driven pulleys.


Edited by camdigger, May 27, 2015 - 08:34 PM.

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#13 holdenboy1960 OFFLINE  

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Posted June 01, 2015 - 08:31 AM

reduction in pullys makes all the difference even 2 or 3 to 1 ratio makes a fair bit of speed change 

in principle 10:1 altered to 13:1 ratio changes speed a lot 

good job too on the make 

 

Shane


Edited by holdenboy1960, June 01, 2015 - 08:32 AM.





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