Heljan bogie gears

[cheesysmith]

I was interested in the way JSW has remotored his 86s in his P4 new street, and how he uses Heljan hymek bogies, being only 1mm short. Having seen how much the second hand hymeks were going for, I needed a different approach. I got the sprues for the hymek bogies from howes of Oxford as spares, and acquired a clayton chassis cheap, decided to dismantle it. I have found that the gears fit perfectly and I now have a motor bogie that is longer that the clayton, and the 3'9" wheels obtained as spares fitted.

 

I now need to find out if all Heljan gear towers inside the bogies use the same gears, but if so, it opens up the possibilities of using the spares and cheap second hand parts to obtain expensive or difficult to get pieces.

[cheesysmith]

I have taken apart a HJ hymek, class 47, and the bogie made using HJ gears from a clayton in the hymek bogie tower obtained as spares. Having taken all of them apart, I have found that they all use identical gears, or near enough. The co-co bogie has a extra pair of smaller gears. You will find attached some photos of the said gears/bogies attached.

 

I have one question, how do you figure out the gears required to buy to replicate the set up shown?

 

 

[Horsetan]

Hmm, I wonder if any of those plastic spurs have a brass equivalent in the Ultrascale range?

[cheesysmith]

Ultrascale already do the replacement axles for the HJ range, so they already have the smaller gears (which should be the same as the axle gears IIRC). We just need the larger gear, the worm and the 2 bearings for it.

[Horsetan]

Ultrascale already do the replacement axles for the HJ range, so they already have the smaller gears (which should be the same as the axle gears IIRC). We just need the larger gear, the worm and the 2 bearings for it.

Interesting. I was wondering if there was any advantage to interspersing the plastic gears with brass ones in between. I have three Heljan Hymeks in P4, all subject to drivetrain experiments.

[billbedford]

The mod of gears is given by:

 

Overall diameter

-----------------------

number of teeth + 2

 

To the nearest 0.1

 

Looking at the photos I'm guessing they are 0.5 mod.

[Horsetan]

Ultrascale already do the replacement axles for the HJ range, so they already have the smaller gears (which should be the same as the axle gears IIRC). We just need the larger gear....

 

I'll be sending in an(other) order into Ultrascale in due course, so I'll take the opportunity to ask whether the small Heljan brass spurs can be bought separately, i.e. unmounted, as well as the cost of a large brass spur.

 

EDIT: there seems a slightly quicker way to get hold of the Heljan-type gears, but not in brass. Currently doesn't take six months to wait, either.....

[cheesysmith]

Come on, DOO tell. A way to get these gears with the bogie towers as spares on the sprue from howes, plenty of repowering options.

[Horsetan]

Come on, DOO tell. A way to get these gears with the bogie towers as spares on the sprue from howes....

EDIT: I'm waiting to see if my enquiry works.

 

The small Heljan gear is about 6.95mm overall diameter, with a centre distance of about 6.09mm, which accords with Bill's 0.5MOD above.

 

The big Heljan gear I will have to extract and measure up.

[billbedford]

There are plenty of 0.5 MOD gears on the internet, here for instance, the problem may be getting ones with the correct bore.

[Horsetan]

There are plenty of 0.5 MOD gears on the internet, here for instance, the problem may be getting ones with the correct bore.

It's a start. Gear width is another thing.

 

EDIT: the large Heljan gear with plain boss is 10.92mm dia. overall, and has 20 teeth.

[Horsetan]

Come on, DOO tell. A way to get these gears with the bogie towers as spares on the sprue from howes, plenty of repowering options.

 

 

UPDATE: the first avenue explored works (I've had a pack of four gears arrive), but is much too expensive, so I will have to look for a cheaper source.

 

There appears to be at least one seller of the 12T gear (in packs, which is helpful) on eBay, so I will have a look at this.

 

The 20T is more of a problem - it's available, but the bore seems to be around 4mm diameter (sleeves to reduce diameter, maybe?) when we only need 2mm.

[billbedford]

Try RB Models. He does both a range of gears and turned knurled centre bushes

 

There is also Mikroantriebe. They are more expensive but give you a bigger range of options.

[Horsetan]

UPDATE: .... at least one seller of the 12T gear (in packs, which is helpful) on eBay, so I will have a look at this.

 

Pack of 20 will be on the way shortly from Hong Kong. Cost: £1.49 - seller doesn't charge anything for postage, which is remarkable.

 

Let's see how they mate with the Heljan original gears, then move on to the 20T cogs.

[Horsetan]

A little plastic bag turned up from Hong Kong this morning, containing 20 12-tooth gears:



....so I took a few out, and tried them in the Heljan Hymek gear casing:



Pleasantly surprised to find that they do mesh quite lightly, and everything revolves, but there is a very slight difference between these and the Heljan originals. The difference is mostly in the thickness of each tooth; the HK gears have thinner teeth than those on the Heljan, and if I put one Hong Kong cog in the middle of Heljan ones, you should be able to spot this:



If you have a Heljan drivetrain which snatches or jams, then one of these HK equivalents might just help free things up a little.

The cost, as I wrote earlier, was £1.49. The eBay seller of these gears didn't even charge for postage!

The next replacement gear to find is the 20-tooth one, with a distance between the 12T and 20T axle centres of 7.95mm. Interestingly, the Ultrascale spur gear calculator reckons this measurement should be more like 8.12mm.

If anyone wants to try these generic gears, the eBay seller's ID is "sellerbible". A variety of different sizes, number of teeth, etc. are available, at unbelievably modest cost.