Trade SDMP/Finney7 - Driving a Geep?

Discussion in 'Resources' started by Steph Dale, 24 February 2013.

  1. Pugsley

    Pugsley Western Thunderer

    Cool! I'd probably use two small motors, hidden in the engine/gearbox castings, one for each end, so they'd both be offset (I think - it's time to refamiliarise myself with DMU drivetrains!).
  2. Steph Dale

    Steph Dale Western Thunderer

    Part the third of the DMU drive gets the motor and drive brackets completed.

    First job is to prep the drive brackets, which I've done on the fret. Comparing with post #283, above, you can see the fixing holes have been drilled out. I decided to use some 8BA cheesehead screws so the holes were drilled 2.5mm, a smidge over the 8BA clearance dimension. Recognising there's lot of ways these brackets could be fitted no fixing screws are provided and the holes have to drilled and tapped if required, by the builder:

    Once they're soldered, cleaned up, blackened and bearings fitted they look a bit like this:

    The motor brackets require a bit more work, starting with the fixing screw holes, as above:

    The right hand spacer is then prepared and checked for the motor front mountings:

    And the left hand one then opened up to take the boss on the back of the motor. I should add at this stage that this fret is supplied with the bores reamed 6mm and a 2mm id ball bearing supplied for the rear mounting of the Canon motor, which has no boss on its back end:

    Once fitted, soldered. cleaned and blackened it looks a bit like this:

    And this:

    More in a mo.

    Rob Pulham, Dog Star and mickoo like this.
  3. Steph Dale

    Steph Dale Western Thunderer

    This is the bit you're going to either love or hate!

    So, depending upon which manufacturer's kit you have it's possible that 'features' will need to be removed from the floor and anyway you choose to do it the fixings for the brackets need sorting. There's a key dimension here in the positioning of the two outer drive brackets to allow for clearances on the universal joints. The motor and central drive bracket can go between, as you choose:

    So returning to a point that I think Martin (Pugsley) raised, I just thought I'd quickly show how the motor can be hidden by the underframe gubbins if it's carefully positioned. I think I've correctly interpreted the Easybuild instructions, but based upon recent experience (and the breakneck pace, more of which later) I can't count on it:

    With all the positions worked out the rib details where the motor sits have been removed (chisel followed by scraping with a curved scalpel) then the holes were drilled and tapped:

    And proceeding at a frightening pace the drive assembled and bogies fitted:

    En route the process has not been without casualties. Along with the scalpel cut to the pad of a finger (yes it does smart a bit when typing) my patience has nearly deserted me. Y'see I got to this point and found there was a definite tight spot and a lot of motor noise; assuming the worst I stripped the drive shafts again and aligned them properly (slacken off the screws a touch, wiggle parts to free running positions, re-tighten) with no joy. Ran the motor up again to a lot of noise, heat from the motor and the sight of a bearing dropping out of the centre drive bracket. I'd missed a bearing with the Loctite, so that was sorted. At this point I thought I'd better run up the motor to bed it in and hopefully reduce the noise. No joy; off the chassis the motor was leaping around the workbench. Not entirely sure what the problem is, I suspect a bent shaft. Whatever; it's knackered so I'll have to get a new one for the full build and means I haven't been able to do any sensible testing. Apart from...:

    1. Grabbing a 6' radius template I locked the bogies off at the desired positions for a 6' radius curve and the drive works very well; it will comfortably go tighter. The dimensions I worked out are accurate. So that's good. I'll be happy to provide that info to anyone who's going to give one of these drives a whirl.
    2. The inclination of the drive shafts isn't as bad as I feared. I knew the sketches were done to 'worst case' dimensions and it's pleasing it's worked out. Also nice to know there's a little bit of a safety net and that the floor being a mm or so above or below the optimum doesn't seem to affect performance.

    There are some pointers to consider before installation;
    Test the motor and run it in before installation (Grr!) infuriating because I always do it; except this once..!
    All manufacturers should test build their products (and ideas) before inflicting them on modellers, sometimes you find the damndest things!
    The extensions to the motor drive using aluminium tube and neoprene tube works well.
    The etched parts also work fine - providing they're used as intended and the bearings retained with Loctite.
    The floor needs to be stiffer than a 'raw' styrene extrusion; accuracy built in during assembly of the drive is instantly lost as soon as the chassis is placed on its wheels. I'll be running a 1/8" square brass section inside the frame rails to solve that problem on this one and I bet a Westdale frame will work very well.

    That's it. I'm pretty happy with the result having learnt a lot in a very short time. I now know I've got a couple of jobs to do in order to build up the rest of the Bubble. But (and the major qualifier) is that as a proof of concept it has worked well.

    Any takers?

    Phill Dyson, tomstaf, Pugsley and 5 others like this.
  4. Dog Star

    Dog Star Western Thunderer


    Your comment about stiffening the underframe moulding rang a bell. You may find a conversation with Ian Norman (@Seahaven) of interest as he had a similar experience with an EZ DMU and needed to stiffen the frame. I recollect that Ian found the underframe was "sinking" in the middle because of the weight of the castings.
    Last edited: 9 May 2015
  5. SimonT

    SimonT Western Thunderer

    two motor option on one chassis with four axle drive for me please.

    With reference to the stiffness, is there anything to gain by placing the motor and all the bearing brackets on to a metal plate, with stiffening webs, and to then bolt the assembly to the plastic chassis?

  6. Steph Dale

    Steph Dale Western Thunderer

    In general terms that's a pretty good solution I think.
    But if you're using two motors you won't have to worry too much about aligning shafts, so I wouldn't feel the need for your particular needs.
  7. Dikitriki

    Dikitriki Flying Squad

    Hi Steph,

    I want a complete kit to drive a 128 please.

    I shall just be driving the inner axle of each bogie; so exactly as you have done yours.


  8. Steph Dale

    Steph Dale Western Thunderer

    Thanks, I'll get back to you off-thread.

    The chassis is with me today at Reading ALSRM show, so if you see a guy with a beard, hat and blue box stocking out the top of his rucksack, it's probably me. Stop me and say hello!

  9. Dog Star

    Dog Star Western Thunderer

    I was accosted by a beard under a hat and offered the chance to inspect...

    The design and production are just so, nice one Steph.
  10. Steph Dale

    Steph Dale Western Thunderer

    Thanks Graham,
    I appreciate the feedback.

    I'll sort the pricing and other details this week, standard motor will be a Mashima 1833.

  11. mth

    mth Western Thunderer

    Have to admitt, it does look better in the flesh.:thumbs:

    Did you show it to Shawn at Easybuild?
  12. Steph Dale

    Steph Dale Western Thunderer

    Yep, I showed it Shawn (and his colleague, who's name escapes me) and they were very interested in seeing the finished article.
    I thought their MetCamm DMU engineering prototype looked very promising too.
  13. Ressaldar

    Ressaldar Western Thunderer

    Hi Steph,

    I think you will find that he answers to - Richard.


  14. Steph Dale

    Steph Dale Western Thunderer

    Pricing for the various components in the SDMP DMU drive is now complete and the full set is available for the princely sum of £99.

    What you get in the set:
    2off 'Blines' 13:1 remote gearbox kits including comprehensive instructions.
    1off Mashima 1833 motor
    1off set of drive brackets
    1off set of motor brackets
    2mm and 3mm aluminium tube for the shafts
    2off universal joint sets
    2inches neoprene tubing to couple the shafts/motor/etc.
    Installation guidance (mostly in the form of the postings on this thread - including the drawings, and an additional set recently completed for shorter-underfame DMUs; the key dimensions)

    What you don't get in the set:
    A DMU; kit, ready to run or otherwise
    Screws/nuts/etc. to fit the parts to the underfame - I can't cover off all the possible materials/part orientations.

    Parts are in stock for an initial batch of sets. This is the standard configuration set as I've shown in this thread; if you want something similar for a specific project (e.g. @SimonT , if you want to use two motors) then please get in touch, I'll be happy to help if I can.

    Pugsley and mickoo like this.
  15. SimonT

    SimonT Western Thunderer

    just for clarity, I presume the bearings are included? I'll try it out on a rebuild of the 103 in the one motor/two axles configuration.
  16. Steph Dale

    Steph Dale Western Thunderer

    Yep the ball-races are included for the gearboxes and drive brackets.
  17. oldravendale

    oldravendale Western Thunderer

    Suitable for a razor edge GWR railcar????
  18. Steph Dale

    Steph Dale Western Thunderer

    I can't see why not, it's essentially a 'universal' set of parts to drive a DMU...
  19. oldravendale

    oldravendale Western Thunderer

    Ooh good. Put me down for one!

    And some drives for 10000/1........
  20. Steph Dale

    Steph Dale Western Thunderer

    Re-arranging the DMU drive components with a few extra items proves to have some rather interesting results...:

    Class22 drive layout 3.jpg

    And yes, this would also work well in Hymeks or other hydraulics. Many US-outline 0-gauge locos also use this style of drive; some to better effect than others. There's a baseplate required to join the components together in this application, which is being worked up at the moment.

    Oh, and for information, mine is D6303. ;)

    Last edited: 16 June 2015