I’ve got an old Blue Box F7B dummy that needs some updated trucks. With some further body detailing, it’s likely to be latched from time to time to some much nicer Genesis and upgraded Stewart/Kato F units. The current visual disparity in the truck details with the Blombergs on those newer locos is rather glaring.
The B unit will remain a dummy as all the others are powered and I’d like to throw my time and money elsewhere. Other than grabs, lift rings and whiskered Kadees it won’t get anything else. No electricals to worry about so I won’t need any pickups on the new trucks. It would be nice to be able to employ the existing pivots that are on the cast chassis but I’m prepared to remove them, then drill and tap replacement mounting holes as necessary. I’m looking for black plastic/delrin and metal wheels if something like that is avaiable. Got any suggestions?
I’m not an expert on it, but my understanding is that the Athearn two-axle plastic locomotive trucks on their F-units and GPs have always been considered very good reproductions of EMD Blomberg trucks. Many folks change the wheelsets out, but the truck sideframes should be good. You might need to ream out the opening for the axles a touch to make them roll better.
I just looked at mine. Mine are plastic, but it’s a one piece casting, and I think the older metal trucks were the same.
The OP will have to find the truck of his liking, and figure out how he can mount it to the frame.
The frame will accept the powered trucks, you could take the gears out of a power truck, to eliminate some drag, and install that, the same way a powered unit goes together, then you’d have the option of removing just the side frames, and replace them with what you want, or a more detailed version of what’s there.
The existing trucks for this Athearn BB are the old cast (white?) metal jobs. In two halves, screwed together with a couple of round head 2-56s at the bolster pivot point. Detail reflects that kind of casting, with a fair amount of flash in or totally covering some of the openings. Wheels are plastic with metal axles.
I’ll get a picture up - after I get back from a trip to the dump. Too many mundane things interrupting the hobby!
I would say the trucks only need replacing if the side frames are the old metal ones. Replace with the plastic side frame version - those plastic Blomberg-B’s were some of the best ever done.
Thanks, Mike and guys. My intial foray using Google came up with two interesting items: 1) the plastic Athearn sideframes seem to be considered the best that have been done, and 2) everything seems to be power trucks. I’d consider just side frames but what to mount them to? I’d also be willing to track down two excess power trucks and gutting the gearing from them, but that leaves what seems to be a major creative effort in mounting them to my dummy chassis. Should Plan B be simply to secure a junker chassis and trucks, gut the gearing, then pop my shell on that?
Attuvian; You mention you would be willing to alter the mounting bolster on the F-7 frame if needed. If so, Kato’s Blombergs are good looking trucks with separately applied swing hanger and brake cylinders. They mount differently than Athearn. They don’t mount at the center of the truck, but are offset a bit. At worst you might need to make new bolsters from brass strip and attach to the frame. Under that wide body that would be hidden with no interference.
The reason I offer this suggestion, if you’re willing to go to the effort, is that I can send you a pair of them that have had their gears removed for other projects. They’ll be fine for dummy use and do have metal wheels. PM me your address if interested.
You can see what they look like if you go on ebay and look for Kato Blomberg trucks HO.
John, I’d be interested in knowing how much of a difference there is between the Kato and the Athearn trucks, as far as the location of the pin from the frame to the truck, and what modifications you did to the frame.
Jim,While correct on the metal side frames the can be replace with the newer trucks…Athearn still list those Blomberg-B’s trucks with the modern frames.
Mike, here’s a side by side comparison of a later BB Athearn truck on the right, with the Kato on the left. The trucks on John’s old locomotive are different from this Athearn truck, so it’s not a direct comparison to his.
Note that the Kato truck’s pivot is off center, I’d say about 3/16 of an inch. It has a nub that would snap into a hole on the frame, held in place by those protrusions on the worm gear cover. The bolster height is close to the same.
John found he had some Athearn BB Blombergs with plastic sideframes, and is going to try to use them, as per our last PM contact. Maybe he’ll post progress here? Dan
I have the plastic version of what John has, and I was going to offer him a set of those, but there still a one piece casting, only in plastic and not the old metal.
Using the trucks that he is, would be the best way to go. He could add metal wheels to that if he wanted to.
The Kato truck pictured is from a Con Cor / Kato MP15. The Stewart / F unit trucks are a perfect fit for the Athearn F frame. I would use a pair of those.
OK, guys, thanks for keeping this thread alive. Southgate notes that I launched the little project yesterday, I remembered that I had an old Athearn GP9 in storage that was a functional dummy as the motor had been removed. Its power trucks have plastic Blombergs. I hauled it out and first checked to see if the two chassis were the same length and I could adapt the Geep’s to take the B unit shell. That would have been simpler but no dice, it was too long. Sorry for this “teaser”: I’ll be out of circulation on the forum for at least the next six hours. I’ll get back later today with the story (and photos) of how this developed.
So I thought. But quickly discovered two initial issues. First, the pivoting face on the Geep truck bolster is about 2.5mm higher than the one on the original cast truck. Second, the casting of the side frames on the original is bad enough that the brake cylinders on the upper edge are merely raised lumps. The separately affixed cylinders on the plastic upgrades stick out about 1.5mm more on each side, restricting the swing of the truck against the drop steps that hang below the body doors. I’m currently woriking out adjustments for both issues. That may require a shift of the king post a milimeter or two toward the coupler platforms. And that might bring into play a restriction to the swing of the face of the gear riser. We shall see what develops. Gotta keep tellin’ myself: “model railroading is . . . .”.
