The path of less resistance? J72 conversion

David Knight
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The path of less resistance? J72 conversion

Postby David Knight » Thu Sep 23, 2010 8:52 pm

I thought it might be helpful to try to show an easier path for converting an engine to P4 and full suspension. I have had an ancient Mainline/Palitoy J72 sitting in my to-do box for a few years now and after a botched attempt with the Mainly Trains kit I decided to give the Bill Bedford frame a try. You see this here before you because Mark Stapleton has encouraged me do do so and because he wants us to have a new engine (or two) for our joint layout's next exhibition in 2012 :oops: Shame works wonders :D

A few illustrations of the basic components follow;
The basic bits.jpg

The etchings.jpg

Finally the heart of the suspension system, Bill's cunning plan to simplify the whole thing. The wire (spring) is held by clips that are part of the etch at the top with modified bearings that ride in purpose built guides all held in place by cosmetic (but functional) spring etchings.
[/attachment][attachment=0]the springy bits.jpg

BTW the usual disclaimer applies, no connection with Bill other than as a customer.

Cheers,

David
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the springy bits.jpg
Last edited by David Knight on Thu Sep 23, 2010 11:18 pm, edited 1 time in total.

David Knight
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Re: The path of less resistance? J72 conversion

Postby David Knight » Thu Sep 23, 2010 8:55 pm

As a note to the above posting, the images went on in reverse order despite my best efforts but the captions should help :oops:

Cheers,

David

EDIT: Thanks to Keith's suggestion the previous error has been corrected. Thanks Keith,

Cheers,

David
Last edited by David Knight on Thu Sep 23, 2010 11:20 pm, edited 1 time in total.

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grovenor-2685
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Re: The path of less resistance? J72 conversion

Postby grovenor-2685 » Thu Sep 23, 2010 9:50 pm

If you click on the 'Place inline' button next to your attachments they will be put into the text of your message wherever the cursor is and you can re-arrange them (by cut and paste) to your heart's content.
You should still be able to go back in to edit it if you wish.
Regards

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Flymo748
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Re: The path of less resistance? J72 conversion

Postby Flymo748 » Fri Sep 24, 2010 5:40 am

davknigh wrote:I thought it might be helpful to try to show an easier path for converting an engine to P4 and full suspension. I have had an ancient Mainline/Palitoy J72 sitting in my to-do box for a few years now and after a botched attempt with the Mainly Trains kit I decided to give the Bill Bedford frame a try.


That bottom photo shows it all. That really is a very, very clever bit of design. I only hope that the coupling rod centres match the axle centres!

Flymo
Beware of Trains - occasional modelling in progress!
www.5522models.co.uk

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David Thorpe
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Re: The path of less resistance? J72 conversion

Postby David Thorpe » Fri Sep 24, 2010 7:25 am

I agree with Fklymo - that looks like a very interesting design. As I too have a Mainline J72 body languishing in a drawer, I'm sorely tempted. I shall however wait and see how you get on with it!

David

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Will L
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Re: The path of less resistance? J72 conversion

Postby Will L » Fri Sep 24, 2010 10:53 am

It certainly looks the business. If it is designed as well as it looks and it makes up accurately (and I'm not trying to suggest it won't), then this could be a very good way of trying out CSB's. Note the properly jointed Connecting Rods!

Think I would still prefer the springs captive in the fulcrums and the block captive on the spring, as I like the way that holds everything together without the need of keeper plates etc. I would suggest the add on springs on this one could be a niggle point.


Will

simonmoore

Re: The path of less resistance? J72 conversion

Postby simonmoore » Fri Sep 24, 2010 7:01 pm

I look forward to seeing the finished product & your final thought's on this kit. I have just been looking for a chassis for a Mainline j72 & didn't realize Bill Bedford did a chassis kit for this loco. Waiting for some money to be sent to me then i am going to order one of these kit's they look simple enough for me to have ago at as a beginner. When i read the instruction's i noticed although it shows how to fit the motor it doesn't give a suggestion as to what is the best choice to use. What motor/gearbox have you chosen ?

Simon.

David Knight
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Re: The path of less resistance? J72 conversion

Postby David Knight » Fri Sep 24, 2010 7:24 pm

A bit more progress to report and a few questions to answer. First off, what was done. All folds reinforced with solder except for the hornguides as I'll explain in a tick. The cosmetic springs can be held in place with 14 BA screws. On the advice of Ted I tried the tap before cleaning anything up and it cuts and works just fine. I have some unused 14 BA screws from an Allan Gibson hornblock kit. Bill's instructions say that for tuning the frame wire across the gap will hold the bearings in place and that the springs can be soldered in place with short guide pins later but I want to be able to take mine apart if need be without messing up the paint. BTW run the tap through after soldering or you'll have to do it over again :? . A 1 mm drill run through the holes in the springs themselves should give adequate clearance

Why I did not solder the hornguide sides yet: there is a need to do a bit of fettling as the bearings vary in width from 3.98 mm to 4.03 mm and the slots are also slightly inconsistent. Not a huge error but there will need to be some matching up done and I want to keep the filing to a minimum. EDIT note dimensional changes I don't know what I was thinking also the clarification on gearbox model :?

Simon, I originally had planned to use a Mashima 1224 with a High Level 54:1 Road runner PLUS which should still fit. Bill's design seems to call for a vertical mount, he does not recommend any particular motor.

Will, Hope the comments about the 14BA screws clarify my position there.
Last edited by David Knight on Tue Sep 28, 2010 1:41 pm, edited 2 times in total.

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Will L
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Re: The path of less resistance? J72 conversion

Postby Will L » Fri Sep 24, 2010 9:53 pm

davknigh wrote:
Will, Hope the comments about the 14BA screws clarify my position there.


It did and it's a valid solution. Actually 12 valid solutions but who am I to quibble.

The motor mount and particularly part 18 on the J72, is like the one provided in the C12 chassis kit, The construction of which I have promised to come back to at some point. I never manger to work out how you were suppose to fit the motor mount on the C12 kit, though I admit I had plans of my own and didn't try too hard to find out, so the J72 instructions has added to my understanding.

An advantage of this style of horn guides is that most (if not all) gearboxes will fit no trouble. The limiting factor to note is the width available between the folded back horn guides.

Will

DougN
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Re: The path of less resistance? J72 conversion

Postby DougN » Sun Sep 26, 2010 10:23 am

Quite Brilliant. I think that Bill/Ted's design is to take the heart ache out of the new chassis building. I have been reading up for the Q6 which will turn up at the door any day now. Dave bradwell uses the same idea of accurate etching to form the horn guide. So as the J72 was my first P4 loco over 14 years ago :shock: (the old perserverance chassis that is) I am quite interested in how the new all singing and dancing will work :D .
Doug
Still not doing enough modelling

David Knight
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Re: The path of less resistance? J72 conversion

Postby David Knight » Sun Sep 26, 2010 11:31 pm

A further update of progress while some of you lot were enjoying Scaleforum :) .

The issue with the bearings turned out not to be a problem at all. As with many of these things they fit in one direction and not the other. All bearings now fit and are identified as to their slots. One point where I might have gone astray was when bending the sides of the hornblocks I twisted from the bottom and as a result the sides tapered rather than being parallel. To cure this I took a large slot screwdriver placed it in a vice and eased the frame down with firm but gentle pressure. It seemed to do the trick.

Drilling the holes in the cosmetic springs benefitted from a jig to support the work. The jig consisted of a small off cut of thin MDF that was placed in a vice with the 'ears' supported on the top edge. The 'ears' were then further supported by a pair of tweezers to keep them from rotating while the 1 mm hole was drilled with a pin vice.

Some time was spent offering up the various frame crossmembers to their intended destinations.

BTW the instructions can be downloaded from Bill's site here;

http://www.mousa.biz/frames/lner_frames.html

Second one down.

Cheers,

David

simonmoore

Re: The path of less resistance? J72 conversion

Postby simonmoore » Mon Sep 27, 2010 9:58 am

Thats great news about the bearings :D I've made a order for my kit & i shall follow your thread & tips to hopefully make mine trouble free. I will order the motor/gearbox & wheels this coming week & hopefully have something to work on this coming saturday. I have been researching a model on rmweb & fotopic to try to find a suitible prototype to model. Look forward to more updates.

Simon.

David Knight
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Re: The path of less resistance? J72 conversion

Postby David Knight » Mon Sep 27, 2010 1:25 pm

Simon,

Glad this thread is of some use. One thing of value is to learn from my mistakes such as the drilling of the spring etches after removing them from the fret when they would have been more rigid if left in place. The problem is my 'inner child' which surfaces frequently. Despite being in my 6th decade, I just can't wait to put the bits together :roll:

Cheers,

David

simonmoore

Re: The path of less resistance? J72 conversion

Postby simonmoore » Mon Sep 27, 2010 2:54 pm

davknigh wrote:
. The problem is my 'inner child' which surfaces frequently. I just can't wait to put the bits together :roll:



I know those 2 feelings all too well i'm 28 but i still feel like that child with his first airfix model aeroplane kit . I don't like etchs to be flat long i prefer them in some state of 3 dimension. Hopefully the chassis kit will arrive before weekend & i have a highlevel road runner +. Gibson usually have wheels to me next day so all being well this coming weekend i can make a start. When you mentioned about the bearings going one way is this in regard to the shape of them & where the hole is positioned?

Simon.

David Knight
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Re: The path of less resistance? J72 conversion

Postby David Knight » Mon Sep 27, 2010 5:08 pm


I know those 2 feelings all too well i'm 28 but i still feel like that child with his first airfix model aeroplane kit . I don't like etchs to be flat long i prefer them in some state of 3 dimension. Hopefully the chassis kit will arrive before weekend & i have a highlevel road runner +. Gibson usually have wheels to me next day so all being well this coming weekend i can make a start. When you mentioned about the bearings going one way is this in regard to the shape of them & where the hole is positioned?

Simon.


About the bearings; I'm not sure about why it works this way but it does ;) probably clever design on the part of Bill. There is bound to be some variation in size but happily it all worked out for me without having to resort to major bodging. After bending up the sides of the hornguides and with the main etch still in the flat I offered up each bearing to the etch to see if it would slide to the top of a slot. If so, grand, if not the bearing was turned through 180 and tried again. Once all the bearings had found a home they and the corresponding slot were marked so they would always be able to be re-matched. I used roman numerals as they are easy to do with a scriber. The marks were made on the top of the slot and the top of the bearing so the orientation would be right. Hopefully this explains things well enough as my camera is not up to the sort of closeups that this would require. If not keep on asking :)

Cheers,

David

simonmoore

Re: The path of less resistance? J72 conversion

Postby simonmoore » Mon Sep 27, 2010 5:23 pm

No that clarify,s what i was wondering i've had some help with my model regarding a prototype & i,m happy to say i have found a critter to model :D
My body is the same as your,s & i need to change it with the different safety don't suppose you know who does castings for these?

Simon.

David Knight
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Re: The path of less resistance? J72 conversion

Postby David Knight » Mon Sep 27, 2010 8:15 pm

simonmoore wrote:My body is the same as your,s & i need to change it with the different safety don't suppose you know who does castings for these?

Simon.


If you are happy with a straight exchange then you might be able to fashion some safeties out of bits of brass tube & rod. If you have access to a lathe or a minidrill you cold try your hand at turning/filing some up. Getting to the point, I don't know of a source but I'll bet someone on this forum can point us in the right direction :)

Cheers,

David

David Knight
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Re: The path of less resistance? J72 conversion

Postby David Knight » Tue Sep 28, 2010 1:49 pm

Sigh, a further correction. My chosen gearbox is the HighLevel Roadrunner + not the straight Roadrunner. My apologies to anyone who was misled by this error.

Progress will slow for a bit as I have to source a new set of axles since the set that came with my wheels are too short :roll: Normal service will be resumed as soon as possible.

simonmoore

Re: The path of less resistance? J72 conversion

Postby simonmoore » Tue Sep 28, 2010 4:09 pm

What wheelsets are you using Dave, Gibson?? I'm ordering my wheels this friday so i thought i best check so i can have a trouble free weekend modeling. Also a quick question regarding fixing the body to the chassis. Today i have been doing a bit of work on the body of my J72 in preparation for weekend & i noticed my body has a front screw fixing & moulded lugs in the metal chassis that fix the body to the chassis is your body the same or doe's it have a fixing at the back?
Also how is the chassis designed with regards to fixing it to the body?

Simon.

David Knight
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Re: The path of less resistance? J72 conversion

Postby David Knight » Tue Sep 28, 2010 5:58 pm

I have Gibson wheels that I got a while ago so there may have been some QC issues at the time.

Mine has the same style of body as yours so I suspect that I will be making a shelf inside the body with plastic sheet and angles and fixing the frame with a couple of screws attached to captive nuts. Besides, this is an opportunity to do up the cab interior ;) . There are suitable holes in the etched frame but they don't line up with anything in the body :shock: There will also be a small matter of filling the gap left in the boiler underside that was previously occupied by the old mechanism but that can wait 'till later. The Mainly Trains conversion had a cast weight but it is a tad eccentric so will need filing first.

Cheers,

David

simonmoore

Re: The path of less resistance? J72 conversion

Postby simonmoore » Tue Sep 28, 2010 7:05 pm

I think that the chassis is built for the later body without the horrible mainline / airfix motor offering. Hopefully i wont have the same issues as you speak of with my wheelset when i order it. Tonight i have been fighting with wire bar to make some pipes for the body & the pipe won :D

Simon.

David Knight
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Re: The path of less resistance? J72 conversion

Postby David Knight » Sat Oct 02, 2010 5:27 pm

Flymo748 wrote:That bottom photo shows it all. That really is a very, very clever bit of design. I only hope that the coupling rod centres match the axle centres!

Flymo


Funny you should mention that. I have progressed to the point that a test fitting of the rods over pointed axles is possible and they fit a treat. The set-up for the rods is foolproof (I hope) as they are set up in their frets in such a way as to virtually guarantee proper alignment if the assembly instructions are followed and you don't break them out of their individual frets prematurely. A cropped illustration will help here.
side rods.jpg

I have already soldered the knuckle pin in place on the actual fret and after cleaning up any excess solder I intend to treat the knuckle area to a coat of gun blue so as to lessen the chances of the whole thing soldering up solid.

Cheers,

David

David Knight
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Re: The path of less resistance? J72 conversion

Postby David Knight » Mon Oct 04, 2010 11:29 pm

Further progress. Some pics of the rods in their frets so you can see how cunningly they are designed including the gun blued bits. The knuckle pin should be obvious as well as the layers built up around it.
coupling rods.jpg


The cosmetic sides have also been added to the main frame structure. This helps make the frame more rigid. Note that the cross brace with ports for the cylinders should be added first and then filed down so the sides do not have an unsightly bulge ;) The remaining braces can be added after the sides go on. The final brace which holds the torque reaction link needs to wait until the gearbox is ready for fitting. You should be able to see the cut-outs where I placed the solder cream. More good design, much easier than trying to sweat the whole thing together.
frame progress.jpg


In both pics you can see a secret weapon that my wife found for me in a Dollar store. They are kiddie clothespins that have been modified so they will grip better and save me from burning my fingers. Dead cheap and very useful.

Cheers,

David

David Knight
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Re: The path of less resistance? J72 conversion

Postby David Knight » Mon Oct 11, 2010 11:49 pm

A little more progress. Thanks to a hint from Ted (thanks Ted) I made a minor modification to the front spacer. The difference is obvious if you compare the pic at the end of the last posting and this one.
further progress.jpg


Holes have been added on either side of the spacer so as to give a clear sight of the wire anchor. You can also see that the wheels are coming together complete with bearings and the rear set has been tried for size and fit (It works ! :D ) One set of nearly finished coupling rods are also visible.

Just a small idea for a jig for filing those pesky top hat bearings.
handy clamp.jpg


Made up from a cheap parallel clamp with a thinned top jaw that has had a 'V' filed in it. Good for the 2 mm or larger variety although I do admit it is a touch stretched to hold the larger bearing shown.

Cheers,

David

David Knight
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Re: The path of less resistance? J72 conversion

Postby David Knight » Sun Oct 17, 2010 11:15 pm

A bit of an update with some pics to show what's been going on.

First off a shot to show wheels & rods in place. I've been right pleased with the rolling qualities when shunted by an existing engine. The pic shows the gearbox partially assembled to help judge where to fix the torque reaction link base.
so far so good.jpg


The rest of this posting is devoted to the brake gear. Bill's instructions show what looks to be a detachable brake gear and rigging in the same manner as Chris Gibbon does with his High Level kits. This is a Good Thing especially with the ability to drop the wheels from the frame that this kit enjoys. The trick is, how to do it? What follows is my interpretation of the drawing built into brass and nickel silver using Bill's etch.

After assembling the main components it becomes apparent that a bit of cunning is needed to make this detachable. For the middle and rear sets the exercise is straight forward, run a length of brass rod through the frame then solder the bracket and brake shoe to the ends of the rod but not to the frame.
brake gear before.jpg


The underpinnings can be done in the same manner not forgetting to thread the activator rods into their places before making the join.
brake gear underside.jpg


Once all this is in place the top cross rods can be snipped off flush with the frame on the inside.
brake gear after.jpg


This will not work with the front brakes. The front pair need to be assembled and separated before assembly as there are spacers in the way that won't let you get in to snip the wire :shock:

We're not finished quite yet but the rest follows along the same lines taking advantage of natural spring to hold things in place. More in the not too distant future.


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