VIN­TAGE SMOKE

THE DIMINU­TIVE CATER­PIL­LAR D3400

Diesel World - - Contents - Spe­cial thanks to Kent Bates, Greg Blasquez, Alan Burns, Cater­pil­lar Inc., Lee Fos­burgh, Ron Nash and ACMOC.

The Cater­pil­lar Trac­tor Com­pany wasn’t the first Amer­i­can en­gine maker to of­fer a diesel, but their en­gines set an in­dus­try mark for power, econ­omy and prac­ti­cal­ity. Cater­pil­lar was the first in Amer­ica to ap­ply diesel power to a pro­duc­tion trac­tor in the form of the leg­endary 1931 Cat 60. It’s not a stretch to say Cat’s D9900 diesel quickly pow­ered Cater­pil­lar to a lead­ing po­si­tion in en­gine man­u­fac­tur­ing and the Cat 60 did the same thing for their crawler line.

Be­fore those first D9900s were bro­kenin, the fa­ther of Cat’s diesels, Art Rosen, had the de­sign teams work­ing on new diesels for an ex­panded line of crawler trac­tors. That new line even­tu­ally in­cluded the 1938 D2, Cat’s first small diesel trac­tor. The D3400 diesel was de­vel­oped es­pe­cially for it, along with the 3400G gaso­line de­riv­a­tive, and both were also in­stalled into the 212 mo­tor grader. The D3400 goes down in his­tory as the small­est diesel en­gine Cater­pil­lar has ever mass-pro­duced.

Start­ing in March of 1939, in­dus­trial power units with the D3400 were in­tro­duced, as well as a marine propul­sion ver­sion. At nearly the same time, Cat added it to their gen­er­a­tor line as the 34-15 Diesel Elec­tric Set, sold in rel­a­tively large num­bers into 1947. With the en­gine run­ning at 1,200 rpm (mak­ing 25 hp and 128 lb-ft), it pro­duced 15 KW (kilo­watts) polyphase or 13 KW sin­gle phase, both at 60 cy­cles. Mounted on a skid and weigh­ing 3,030 pounds, it was portable and ver­sa­tile. Prop­erly ser­viced 34-15 gensets could, and did, run for decades with­out ma­jor work.

The D3400 en­gine was a wet-sleeve, in­di­rect-in­jected, four-cylin­der diesel dis­plac­ing 221 cu­bic inches from a 3.75-inch bore and a 5-inch stroke. The crank­shaft was sup­ported by five main bear­ings and the high­est no-load rat­ing listed was 1,525 rpm, with a peak power

rat­ing of 35 hp at 1,500 rpm. Those higher rpm in­ter­mit­tent rat­ings were seen on the D2 crawler and 212 grader or the marine propul­sion en­gines. Gen­er­a­tor con­tin­u­ous rat­ings ranged from 25 to 31.5 hp from 1,200 to 1,440 rpm.

The Cat D3400 Goes to War

The war dom­i­nated Amer­i­can in­dus­try through the first half of the 1940s and, of course, the D2 crawler and 212 grader joined up and went to war wear­ing OD paint. So did the 34-15 gen­er­a­tor sets and many other Cat prod­ucts. Less known are the Cat D3400 en­gines that went to the Navy and Mer­chant Marine for in­stal­la­tion into ships as backup gen­er­a­tors. We dis­cov­ered a Cat D3400 aboard the SS Red Oak Vic­tory (see side­bar), a World War II cargo ship that

served both the U.S. Navy and the Mer­chant Marine. It’s orig­i­nal to the ship and drives a 15 KW, 240-volt DC (Di­rect Cur­rent) gen­er­a­tor that was, and still is, used as backup power.

Cat Evo­lu­tion

The D3400 en­gine was pro­duced from 1938 into 1947, with 19,161 built for the D2 trac­tor, 1,797 for the 212 grader, 6,047 for gen­er­a­tors and power units, and 216 as marine propul­sion units. Ad­di­tion­ally, 2,492 3400G gaso­line en­gines were pro­duced from 1938-42 and were among the last gas en­gines Cat built. Start­ing in 1947, the D311 series en­gines (251ci), re­placed the D3400 and be­came Cat’s small­est diesel. The D311 had di­men­sions and ar­chi­tec­ture sim­i­lar to the D3400, but a larger bore, a cross­flow head and more power (57 hp @ 2,000 rpm).

By the end of the 1930s more than a third of Cater­pil­lar’s in­come came from diesel en­gine sales and it just went up from there. Post­war, Cater­pil­lar in­creased its line en­gine of­fer­ings and is still a lead­ing man­u­fac­turer of diesels known world­wide.

 Still serv­ing! Built in July of 1944, this Cat D3400 diesel has been aboard the SS Red Oak Vic­tory since the ship was com­mis­sioned and cur­rently has 683 hours on the clock. This gen­er­a­tor set dif­fers sig­nif­i­cantly from the 34-15 AC (Al­ter­nat­ing Cur­rent) units Cater­pil­lar built in-house. DC power was re­quired for marine op­er­a­tion, so Fabick Broth­ers Equip­ment Com­pany in Sike­ston, Mis­souri, took spe­cially built D3400 en­gines and added the Ideal Elec­tric 15KW DC gen­er­a­tor heads and the other gear needed for a ship­board in­stal­la­tion. This D3400 car­ries an “SP” suf­fix in its se­rial num­ber, in­di­cat­ing Spe­cial Parts in­cluded by Cat. Those in­clude a wa­ter-cooled ex­haust, dual oil fil­ters, elec­tric start, a higher rated rpm (1,440 vs. 1,200) and a higher 31.5hp rat­ing. The sil­ver paint was ap­plied at Fabick, OD green be­ing its orig­i­nal color.

 Place­ment of the backup gen­er­a­tor var­ied among the Vic­tory ships, of which there were four com­mon sub­types. It was al­ways in the su­per­struc­ture above the hull for a good rea­son; it was well out of the way in case of ma­jor da­m­age in the en­gine room or hull flood­ing. Power could be main­tained even as the ship was sink­ing. On the Red Oak Vic­tory, the backup gen­er­a­tor was placed on the boat deck (sec­ond up from the main deck) of the su­per­struc­ture. The cover be­hind the “Oak” on the sign is the ra­di­a­tor out­let, which would be opened when the en­gine was run­ning. Alan Burns, a re­tired naval of­fi­cer and now a vol­un­teer aboard Red Oak Vic­tory, stands by af­ter al­low­ing Diesel World ac­cess to the gen­er­a­tor. The backup gen­er­a­tor com­part­ment isn’t part of the nor­mal tour but the tour guides can show it to you by spe­cial ar­range­ment.

 Un­like most of the land-based gen­er­a­tor sets and power units that used a 2-cylin­der gas pony en­gine to start, this ver­sion is elec­tric start. It is cooled via a ra­di­a­tor with a blow-thru fan that pushes air out from the com­part­ment. The ra­di­a­tor shell also in­cor­po­rates a very large oil cooler. Cat built its own in­jec­tion pump and in­jec­tors that popped at 1,750 psi. The day­tank above the en­gine holds about 100 gal­lons and with the en­gine burn­ing 3.3 gpm at a full load, that’s about 30 hours of run time to a dry tank.

 Much of the small com­part­ment is taken up by a power dis­tri­bu­tion panel. This is old-school stuff but the unit still works as de­signed and when main power from the ship’s two 300 KW steam turbo-gen­er­a­tors drops off, the old Cat will au­to­mat­i­cally fire up and take the load within 20 sec­onds. It can­not take the ship’s en­tire elec­tri­cal load, but it feeds the most vi­tal equip­ment. This in­cludes emer­gency light­ing, com­mu­ni­ca­tions, gyro com­pass, cer­tain pumps in the en­gine room, the elec­tric an­chor wind­lasses, and a cap­stan lo­cated on the stern.

This is a place all Cat fans should visit! As Cater­pil­lar’s small­est diesel, the D3400 is an im­por­tant part of her­itage dis­play at the Doug Ober­hel­man Visi­tor’s Cen­ter at Cat’s Peo­ria, Illi­nois, head­quar­ters. Shown here is a re­stored 34-15 gen­er­a­tor that’s a part of the ex­hibit. It was re­stored by Kent Bates, a re­tired En­gi­neer from the Cater­pil­lar En­gine Di­vi­sion. Bates had a 35-year his­tory with Cater­pil­lar and has a pas­sion for the com­pany’s old gear. This unit was built in 1947, the last year of pro­duc­tion for the D3400 and the 34-15 gen­er­a­tor. Re­port­edly, it was the backup gen­er­a­tor for an Illi­nois hospi­tal. Yel­low paint is the “tell” for a power unit built af­ter WWII. Dur­ing the war, all Cat equip­ment was painted mil­i­tary Olive Drab, even the small amount of stuff built for civil­ian use.

Im­age by Kent Bates

 This is a 1941 Cat D3400 power unit and you can clearly see the two-cylin­der, 10hp gaso­line pony en­gine mounted over the bell­hous­ing and geared to the fly­wheel via a clutch. The pony en­gine could be man­u­ally started with a rope or, as shown, with a 6-volt starter/gen­er­a­tor. Re­stored by Kent Bates, it’s now on dis­play at Cater­pil­lar’s en­gine plant in Peter­bor­ough, Eng­land. The his­tory of this unit is un­clear but it came from Michi­gan and was pos­si­bly used at a mu­nic­i­pal wa­ter plant. You will be won­der­ing about the gray paint ver­sus the yel­low in the other im­age. Though the trac­tors were yel­low af­ter 1931, Cat painted its in­dus­trial en­gines gray prior to World War II. Af­ter the war, ev­ery­thing got the sig­na­ture Cat Hi-way Yel­low.

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