GEA, a 3.5'' live steam narrow gauge locomotive

[Henk]

So on to the hornblocks guides. Machined from 10x10 mm, with a length such that there are two from each length.

And in the vice:

I was a bit worried that there was not enough meat held in the vice, but I could do 0.75 mm depth, which was OK I guess. I am still a bit squeezy about getting too much smoke from the cutting oil. I do not want to ruin my cutter.

And there are 8 sufficiently equal parts.

And before rivetting onto the frame plates:

And after:

I did find that (not unexpectedly), the tolerance of drilling and riveting is not really 0. The actual slot inner dimension between 24.80 and 25.00 with the nominal size 25 mm. Parallelism of each slot is OK I guess (say .03 mm max). As I have not made the hornblocks themselves yet, I may end up making the dimentions of those slot specific. But then again, that is of course less satisfying. So probably what I will do is target the hornblocks a bit under 25, and see whether the natural variation will suggest to assign them to a specific spot, or that I need to skim the guides.

 

[kvom]

Locomotives can't be machined too precisely as you undoubtedly know. I've been advised on my build that they should be made "halfway worn out". The axle boxes will need room to flex.

 

[Henk]

kvom,

Sorry, I missed your reply. Actually I did not know about the halfway worn part for locomotives. Thanks for that piece of info. In the mean time I have fitted the hornblocks (before finishing them fully though), see next post. BTW, this happened to me before, getting good advice, which I only digested after already having continued. I should probably improve there...

I have wondered about the amount of play one should built in for sideways movement of the hornblocks. When there is not play at all, then the axle does not have the freedom to have the left hand side higher / lower than the right hand side. So I indeed targeter for a not so tight fit sideways (0.2 mm). I hope that is sufficient, otherwise I need to increase play there.

Henk

 

[Henk]

The hornblocks themselves were machined from a single bar of "some steel". Sorry, I do not know how to distinguish hot rollled from cold rolled. I guess it is just st-37 (and I do not know the international term for that other than just plain iron). It machined nicely.

Flycutting:

I was not really happy with the surface finish, but at least there were some marks form both sides of the cutter -though there was a clear dominance from one side. So tramming was not too bad.

No pictures from milling the side recess, but nothing spectacular.

Sawing of the individual pieces:

Yes, I would like to have a bandsaw, but I cannot afford to reserve the space it would need. And to be honest, it only takes 5-10 minutes to cutoff (each), and it almost feel like doing honest work!

Finishing off in length + smoothing some edges:

Though of course this is not visible, I was quite happy with the tolerance on the length, they were all within +/- 0.02 mm. This dimension is completely uncritical, but I try anyway - and only throw away stuff when it is not usable.

Henk

 

[Henk]

So I stil had the problem of fitting the hornblocks to the guides. I considered milling the guides, and started making a milling setup:

The round bar between the frame plates and the glue clamp are there to improve rigidity. However, after making this setup, it dit not feel anywhere near stiff enough to do decent milling. Surface finish would be horrible, and I really needed to take off just a few 0.01 of a mm.

So I decided to use a file instead, and put some tape around the other end.

Because there is the guide on the other side, one cannot accidentally file under the wrong angle. I was very glad with this, as I do not consider myself brilliant on filing. I did notice that because one cannot really put any pressure, the metal removal rate was very low. This suited me fine - I only wanted to remove a little material.

So now I have the four hornblocks fitted (in this picture they are still a tight fit, but afterwards I did some more carefull filing, and now they are all a nice sliding fit)

I also got to use the engineering blue (not on any picture) to show the high spots. That tube had been waiting for two years to be used, but it really was helpfull.

Henk

 

[Henk]

One hornblock bored:

The instructions proposed a production method I did not really like. It involved first boring, slit-sawing out the inner block, inserting a piece of brass with the same thickness as the saw. I choose to make a little block inside first - I felt it was then easier to retain accuracy between inner and outer block. The position of the inner block is maintained by a little pin that is barely visible (left hand side of left block). Were I to do it again, I would probably increase the size of the inner block. It is now nominally equal in size as the hole itself. This leads to a very sharp edge internally. After it has been fully assembled, this will not be a bother, as there will also be bronze bearing shells anyway. But still, it does not look right when it is disassembled.

 

[Henk]

Then the bearing shells,, two bars of bronze soldered together:


Turned with parting line on center.


Then a minor mishap: After boring and reaming of the last shell, I noticed after I took it out of the collet, that one side of the solder joint came loose. I turned the OD down a bit, and press-fitted thin ring on both ends.
That is how the following ugly duckling came to be:


Turning dow the center part on a spigot posed no problem. I had a little sweat when turning down the edge, but that was also no problem. The reatining nut put in enough pressure to stabilize it. You can see the remnants of the two rings hanging there.

Which makes current frame status as follows:

 

[napoleonb]

Dat ziet er vreselijk mooi uit Henk, petje af.

Really nice solution for that riveting. I'm awaiting the parts for my Decauville 020 to arrive from the laser-cutter and was thinking what to do with the rivets as I want to be able to dissassemble it.

 

[Henk]

Thanks. For the rivetting I would love to take credit, but must admit that I am just following the instructions.

Also for some reason sometimes the photos look better than reality. And you probably understand for some reason that these photos have a higher likelyhood of ending up over here!

 

[Herbiev]

Coming along nicely Henk. Great work. Great pictures.

 

[Henk]

Now back to the wheels. They needed the profile of 3 degrees and the axle hole bored. I had already beveled the spokes. For the latter I had to rechuck the wheels in the rotary table and 4 jaw. This was easier than I had anticipated. As a side note, apparently it is possible to align stuff in the rotary table by ~ 1 deg.

Profiling:*

This is done in a single setup on a simple jig in the 4-jaw. Nothing spectacular - just rather time consuming. The radius of 1 mm I did with 'manual cnc' with steps of 15 degrees.

There was the issue of one of the wheels with a few holes drilled on the wrong (i.e. The counterweight side) places. I want to really press fit the wheels onto the axles - this is a new operation (and level of accuracy) for me. So I thought it was a good idea to get some practice and also press fit some rods in there.*

This was a good practice, which reinforced my intent of indeed press fitting the wheels.Then some cleaning up of this wheel. You can still see the four former holes.*

 

[kvom]

As you likely know, opposite-side wheels need to be accurately quartered to prevent the side rods from binding. For a press fit this will require some sort of jig to align the second wheel on the axle.

 

[Henk]

Kvom,

I am aware of that. I really do appreciate any feedback such as your help. The jig is already done, see below.*



It's built-up and I opened up the axle holes opposite from the cranks. This should ensure maximum accuracy in that direction I think, while still allowing taking the finished axle from the jig. The biggish holes on the left are non functional- they happened to be present in the scrap I had lying around.

The axles I did not turn between centers.*My experience in turning between centers is that after a while, there was always a significant play on the tail end.

I dialed them into the 4 jaw to less then 10 um tir, turned one end, end then flipped it (and of course dialed in the other end).*
With a succes rate per side of close to 50% you can imagine there is quite a number of 110 mm pieces of silversteel in my scrap bin.*The diameter on the axles side I targeted 10.04 mm with at most 5 micron deviation. The axle holes are 10.02 mm.*

But before using the quartering jig, first I need to get the crank pin holes to size and in correct position on the wheels.

Henk
P.S. Apologies for the stars with each return character i typed this message in my email program and the stars appear after copying.*

 

[RonGinger]

I missed this thread when it started, great job and nice photos.

I am in Boothbay Maine, and we have a narrow gauge museum here that has 4 engines that look exactly like your model- They were made by Henschel in Germany. Here is a link to a page that shows some of the activity there. http://plsntcov.8m.com/BRV/Railroad1.htm

Are there plans for this engine? I have often thought of modeling one, but the work of measuring and drawing plans has put me off..

 

[kvom]

On my loco I used Loctite 620 with a slip fit to fasten the wheels to the axle, rather than pressing. I felt more comfortable with that, and it was easier to have a do-over (heat joint with torch and press out).

 

[Henk]

Hi all,

Long time no posting - mainly due to slow progress. Life and stuff.

I will pick up where I left off - I just have to dig into my memory for some parts. And also now progress will be slow, but I am not in a huge hurry.

So pressing the wheels onto the axles, using the jig I showed above.



Minor issue is that there is a small wobble. I do not know yet whether this will turn out to be a problem. I'll see after I tested the frame on its wheels on a track. As to the why of the wobble, The vice is not perfect to keep the pressing force perpendicular to the axle. BTW: long time ago I did get a small press for exactly this action... I just forgot to take into account that the full axle AND the wheel thickness needed to fit in. Bummer. So I considered myself lucky not having to get a bigger one and had this vice lying around to do the job. Maybe I should have gotten the larger press after all.

 

[bazmak]

Nice work,i will be following this post with interest,it brings back happy memories.I would like to add comments
1 Making the wheels from solid i assume without CNC is not easy and i think you are doing an excerlent job
2 I assume you predrilled a couple or more suitable holes and bolted the frames together before drilling and machining completely as a pair ?
3 One of my big problems was drilling the crankpins accurately and great care care with quartering the wheels.I made a drilling fixture and a jig but found way down the line tight spots in the connecting rods.Very difficult to overcome
without great accuracy
4.I made a tapered mandrel,mounted the wheel between collet and tailstock centre and final turned the outside of the wheels/treads at the same setting
My congratulations so far and i will be following this thread with great interest
If you read up on other models no matter how different, setups jigs and fixtures
are very similar in showing the best/easiest methods to make different items
Regards Barry

 

[Henk]

>Making the wheels from solid i assume without CNC is not easy and i think you are doing an excerlent job

Thanks - admittedly I think the wheels look better in photos than in real life. Given the amount of work I guess it would have been wiser to not do spokes. but then again those spokes were my main excuse for getting the turn table in the first place.

I assume you predrilled a couple or more suitable holes and bolted the frames together before drilling and machining completely as a pair ?

yep

3 One of my big problems was drilling the crankpins accurately and great care care with quartering the wheels.I made a drilling fixture and a jig but found way down the line tight spots in the connecting rods.Very difficult to overcome

Though I have progressed somewhat, I am still not 100% sure that the quartering is good enough - so I keep my fingers crossed.

Henk

 

[Henk]

Here's a pic with the frame on its wheels.



With a lot of imagination there is a resemblence to a loco. I do think I need to loosen up the hornblocks somewhat to have a nice springing action. Specifically the allowed tilt of the axles needs to be increased.

Henk

 

[Henk]

The very rustig start of two connection and two coupling rods :

For one rod ( in the front) the thickness has already been reduced from 6 to 5 mm.
They would take an incredibly long time to finish. I think this picture is 20 months old.

Henk