Archived

This topic is now archived and is closed to further replies.

Old Pokey

tandem d9s picture.

7 posts in this topic

I cam across this setup at the great oregon steam up. It is 2 cat d9s hooked together with what appears to be air controls to the slave machine. I've seen similar stuff on here before, but was wondering what the advantages and disadvantages were. I imagine pulling scrapers on a hill would be one reason. Were they reliable?

Share this post


Link to post
Share on other sites

Cat called them Double D9's, as per the model decal DD9H. That particular model, had 410 hp per tractor, for a total of 820 flywheel hp.

They were used mostly for slot dozing, or for pushing large scrapers like 657's or 666's. They never were too popular, as they were not terribly manuverable, and needed an operator that was not "asleep at the wheel". You are right about the air controls. The operator rode the front machine, and the air controls for the rear machine were hooked together with the controls for the front one. They also had a side by side version, which they appropriatly called a SXSD9. I think they were equipped with a 24 ft. dozer.

Share this post


Link to post
Share on other sites

They actually called them "Quad-Trac" back in the late 60's. 2) D9G's for a combined hp rating of 770.

The side by side D9H's were called "Double Dude" these were built from '74 to '77. They had a 48' blade & total weight was 183,000#'s and a total of 820hp.

A contractor named Buster Peterson came up with the idea back in the 60's & he later sold the patent back to Caterpillar.

I have a pic around here some where I'll see if I can find it.

IH RD

Share this post


Link to post
Share on other sites

i worked for a farmer that ran double dudes and he said that they were a back and forth unit for pushing the big pans he said that you avoided turning one at all costs .

Share this post


Link to post
Share on other sites

Sounds like they were more common than I ever thought. I cant imagine that much horsepower on steel tracks. :o That has to be impressive to hear and stand next to as it drives by.

Share this post


Link to post
Share on other sites

Cool Tandem D-9 pics. Courtesy of ACMOC Board.

post-1574-1127273268.jpgpost-1574-1127273315.jpgpost-1574-1127273336.gifpost-1574-1127273380.jpg

IH RD

Share this post


Link to post
Share on other sites

Hi, Old Pokey.

IH RD is right. They were an attempt to get more grunt for push-loading pans.

Apparently Buster Peterson did an experimental version with, I think, 2 A-C HD16's side by side with the middle tracks removed and the two engines joined by a frame which led to the 'Siamese' D8's, 2 x 2U series Cat D8's joined side by side in the same fashion. Only 3 of these were ever made.

As I understand it, he later turned his attention to the concept of 2 tractors nose to tail for more grunt for push-loading and came up with the Dual D9G or DD9G, or Quad-track. When the D9H came out, he did ditto with them. At that time, Cat and Peterson Engineering were using the same enginering protocols to facilitate moving production from one company to the other. Cat used Buster's ability to get an idea or concept

'into iron' quickly to get several different projects up and running faster than they could do it themselves. (Buster had previously worked for R. G. LeTourneau for some years before joining one of the other Peterson brothers at Peterson Engineering.)

The dual D9's did require a wide-awake operator not the least because you had more machine length behind you that in front of you. I have never operated one but some men who had told me that you could not turn sharply travelling forwards with both units under full power because the back one wanted to push the front one sideways and turn it over. How true this, I don't know but I can imagine that it might be a problem.

Almost all were built for push-loading work and were equiped with cushion dozer blades for this reason although some were also equipped with rear-mounted rippers on the back tractor for ripping work as well. Also, as per the photos above, some were equipped with the Collins Giant ripper for sub-soiling work, ripping deep hard pan, often with one or two more D9's either pushing or pulling.

Hope this helps.

You have a wonderful day. Best wishes. Deas Plant.

Share this post


Link to post
Share on other sites