 Joined: 18/04/2022(UTC) Posts: 29 Location: New South Wales, Sydney
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Dear Forum members, I am replacing a set of connecting rods from a Trix 22458. They are a prefabricated part that clips in at the front with a plastic split pin that clips into the driving wheels. I have attached a screenshot of the exploded spare parts drawing and the part is number 15 on the diagram. The original part broke where the plastic split pin inserts into the wheel. The loco has been disassembled, the old part has been removed and the new part is on the way from Marklin. I presume it is a simple matter of clipping the new assembly in at the front, orientating the wheels correctly and then pushing the split pin into the driving wheel hole. Are there any pitfalls or tricks that I need to know before replacing the part. It seems pretty straightforward but I thought I should check before risking damaging a new part and starting over again. Any advice welcome. Rob 
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 Joined: 04/02/2011(UTC) Posts: 3,563 Location: Paris, France
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Hi Rob No this is delicate work that calls for - removing the loco's body - removing the tiny rod screws and washers and remember where they were). On some models they are different depending on the axle. - removing the screw (circled in green) attaching the distribution frame (circled in red). Attention there are washers / insulation parts - dis-engaging the piston rods and guides from piston  To assemble proceed in reverse order Check that all screws are tight (not too much) and that the rods are moving freely no matter the sideways play of the axles Cheers Jean |
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Joined: 18/04/2022(UTC) Posts: 29 Location: New South Wales, Sydney
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Hi Jean,
Thanks for the tips. The loco has been disassembled and the broken part removed. I did note the insulating washer and also the connecting rod spacing ring.
My main areas of concern were the order of reassembly - ie does it matter if you attach the new assembly to the wheel first of engage the rods and guides to the piston or the other way around. From your post I think you are suggesting the former rather than the latter. The second issue is the orientation of the connecting rods. It seems to me that it just has to be the reverse of the other side. I am planning to see where the other side sits and then rotate the wheels 180 degrees and replicate the position of the valve gear on the side to be repaired. I may be mistaken but the hole in the wheel for the pin looks to be slightly rectangular in shape, suggesting that there are only two possible positions for the plastic split pin. That being the case, the orientation of the valve gear can either be correct or 180 degrees out - rather than just a little bit out if the hole was circular, but I could be mistaken about this.
The parts have arrived in Australia and with any luck I will have them this week, so I should be able to attend to this next weekend.
Rob
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 Joined: 05/12/2008(UTC) Posts: 1,801 Location: Crozet, Virginia
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Originally Posted by: Rob11966  The second issue is the orientation of the connecting rods. It seems to me that it just has to be the reverse of the other side. I am planning to see where the other side sits and then rotate the wheels 180 degrees and replicate the position of the valve gear on the side to be repaired.
Hey Rob, You are on the right track so to speak. But one side of a steam loco drivetrain is out of phase with the other by 90 degrees, not 180. Even though these rods are driven by the wheel and not the other way round, a model steamer will not operate unless the wheels are properly quartered. It works like that becuase the pistons are double acting, and that means four power inputs per wheel revolution, two from each cylinder. |
Regards,
Jim
I have almost all Märklin and mostly HO, although I do have a small number of Z gauge trains!
So many trains and so little time. |
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Joined: 04/02/2011(UTC) Posts: 3,563 Location: Paris, France
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Hi Rob Originally Posted by: Rob11966
My main areas of concern were the order of reassembly - ie does it matter if you attach the new assembly to the wheel first of engage the rods and guides to the piston or the other way around. From your post I think you are suggesting the former rather than the latter.
I thiink it is best to do things in this order: - position the wheels so that wheel screws are accessible - engage the piston rods and the guide bar into the piston - attach the distribution frame to the loco chassis - attach the rods and coupling rods (copy cat the other side of the loco (washers and which connecting rod goes external to the other) - often, the wheel screws near the pistons are shorter to avoid jamming with the connecting rod (from the piston) I don't have a large experience. I did this on this loco a KPEV T16 (37166)  Cheers Jean |
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Joined: 18/04/2022(UTC) Posts: 29 Location: New South Wales, Sydney
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Ok Jim,
Thanks, that's really useful. I'm glad I asked the question, and it just goes to show that you don't know what you don't know!
I will have to look closely at an intact model and play with the wheel orientation - I am spatially confused now, complicated by the fact that the 1 o'clock position on the right side is orientated forward and the 1 o'clock position on the left side is orientated backwards.
Rob
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Joined: 18/04/2022(UTC) Posts: 29 Location: New South Wales, Sydney
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Thanks Jean, The order makes sense, thank you. All I have to do know is work out the orientation of the wheels with respect to the 90 degree phase shift. I have to get my head around that! Rob Addit - I have just had a play around with a functioning loco and I have worked it out. I can see the wheel counterbalance weights are offset on either side by 90 degrees. Therefore, when the wheel counterbalance weights are directly downwards on the right side on this particular locomotive, the wheel connecting rod is orientated at approximately the 7 o'clock position when viewed from the right (orientated forward with respect to the front of the loco). When I move the loco forward so the left hand counterweight (on the corresponding wheel) is orientated directly downwards, the wheel connecting rod is at the 7 o'clock position when viewed from the left (orientated backwards when compared to the front of the loco). This then places the connecting rods 90 degrees out of phase. It's hard to describe, so I have attached two explanatory photo's, but I think I have worked it out correctly now.  
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Joined: 04/02/2011(UTC) Posts: 3,563 Location: Paris, France
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Originally Posted by: Rob11966 The order makes sense, thank you. All I have to do know is work out the orientation of the wheels with respect to the 90 degree phase shift. I have to get my head around that! Hi Rob Yes indeed driving wheels are "quartered" and they all must be quartered in the same "direction" (e.g. Left side is 90° clockwise ahead of the other side) This is quite easy to see if one of the wheels is installed in the wrong direction. On a normal distribution gear change, you don't have this issue as the other distribution gear remains in place. I am sure you are quite there Good work Jean |
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Joined: 05/12/2008(UTC) Posts: 1,801 Location: Crozet, Virginia
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Following up on Jean's advice, which as usual is correct.
If the bolts on the right side are at 12:00, those on the left side are ahead and at 3:00. Or if the right side is "rods down" where the bolts are at 6:00 the left side rods would be at 9:00. It is also important that all wheels on a side align at the same position. Once you start playing with it I think it will be pretty obvious. |
Regards,
Jim
I have almost all Märklin and mostly HO, although I do have a small number of Z gauge trains!
So many trains and so little time. |
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Joined: 18/04/2022(UTC) Posts: 29 Location: New South Wales, Sydney
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Thanks everyone, The part arrived yesterday and I attempted the repair this evening. Jean, I followed your advice and the steps as you outlined. It is actually quite fiddly as you indicated - the parts are very fragile. Jim, thanks for the encouragement, the orientation of the connecting rods was pretty straightforward when I got into it - however, I may well have messed it up, if not for the advice. I also had some soldering of pickup wires to the front circuit board. Unfortunately not my neatest job but I guess perfection can be the enemy of good, so I left it alone. Anyhow, I am pleased to report a happy ending after all of that - it now works perfectly! Thank you to everyone for the advice. Repair complete! 
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 2 users liked this useful post by Rob11966
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