SD70M - Powered

Post details of your rolling stock developments - locomotive, carriages, DMUs, etc.
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Re: SD70M - Powered

Post by Slarge »

Do anyone know what the exact specification of the gears that are used in all T-Gauge trains?
Gears are all M0.15, the numbers of teeth are as follows:

The first gen gearbox (103's)
Motor 10. Crown 24/10. 32/10. 45. Wheel 10.

The second gen gearbox (9000)
Motor 10. Crown 24/10. 24/18. 24/10. 45. Wheel 10.

I had noted this down a year or so ago from a translation of the German forum: http://web109.s1.deinserver.net/t-gauge/forum.php
The post was by the T-Pioneer: Uwe Fenk http://www.uwefenk.de/QTT.htm

you can buy gears & worms here http://www.shop.kkpmo.com/index.php?cPa ... f708dd9cad

Hope it is of some help.
Your model is looking insanely awesome, i wish i had the time to dedicate to t-gauge, how is your 2-10-0 coming along?

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ConnorL
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Re: SD70M - Powered

Post by ConnorL »

Perfect! Thank you! I ordered the right one! I am still wondering why my gearbox still jams, I tried the toothpaste and cleaned it extremely well...no changes, tried adding ultra-thin lubricates...still no changes.

I made the gears extremely loose so they can move freely, I am wondering if I made them TOO lose causing problems? Is it better to have the gears that is tight in place, that can be worn down or...?

I'm becoming little concerned about how my project is progressing right now...It seems that the motor is unable to provide a large torque to overcome the friction. I might have to modify the chassis to add gear ratios.

About the Santa Fe 2-10-2, I am putting it on hold...I realized that I'm jumping from one project to another wasn't a good idea as they made the overall project slower. I decided to go ahead and finish what is the easiest and what is almost done.

Either ways...it's all about Trials and Testings! Not everything is perfected at the start, I'm trying to get it reliable enough so any future shoppers won't have any problems that I'm having right now.

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Re: SD70M - Powered

Post by Slarge »

The only other thing i can think of is that the gears could be too close together, or not have sufficient under cut Image.
The other thing i did notice is that on the largest gear, the one that connects the gearbox to the wheels, is that this gear has a bevel across the teeth, i assume this is to reduce friction as the wheel bogie pivots when going around a bend.
That said if you can leave it running for a period of time the friction may reduce through natural wear-and-tear?
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ConnorL
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Re: SD70M - Powered

Post by ConnorL »

I still can't figure out what the problem is.

I'm hoping anyone can see it, I had the gears and the worm measured to the nearest specification.

Image

Thanks

I was thinking the middle gear is too loose? (See the half-circle gap of the bogie and the gear hole itself)

GarrattHamster
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Re: SD70M - Powered

Post by GarrattHamster »

Hi ConnorL

It maybe me. But i think it could be the worm gear. the Diameter of it could be a fraction to big or the Hmmm teeth section maybe to much in leanth. I am sorry if i don't make sense. my mind and the termoligy is not as it use to be :|

ConnorL
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Re: SD70M - Powered

Post by ConnorL »

So are you saying that the wormgear's diameter should be smaller/larger? Or should the middle gear be smaller/larger? Or do you mean the teeth in the wormgear is too thick?

The wormgear isn't 100% accurate, I had hard time modeling the teeth. In the picture it might be little off, but thanks for the suggestion. I'll try it out.

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dkightley
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Re: SD70M - Powered

Post by dkightley »

Manufacturing such precise mechanical components always has its difficulties.

The accuracy of the individual components cannot always be relied upon as being as good as the customer expects...or the supplier can provide.

Being realistic, we need to design things with a good dose of allowance for misalignment, shrinkage, deformation, and any other physical anomoly that might creep in.

With the fact that we're not talking about transmission of high power or torques, its best to err quite markedly on the side of ensuring there's plenty of space/slack to allow for the inaccuracies. I don't think theres any danger of designing in too much slack in gear meshes....unless the gears actually drop out of mesh. On the other hand, should gears be too tight meshing, then the jamming symtoms as described could happen. Particularly regular jamming when gear trains are run under no load.

And lets not forget the issue might even be caused by a combination of "ovality" in both a shaft and its journal....causing tightness once or twice a revolution.

This is one of the joys of T gauge. It's size introduces challenges that don't exist in larger scales..... ;)
Doug Kightley
Webmaster here and volunteer at the National Tramway Museum http://www.tramway.co.uk

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dkightley
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Re: SD70M - Powered

Post by dkightley »

I was thinking the middle gear is too loose? (See the half-circle gap of the bogie and the gear hole itself)
Having looked closer at the drawing, I'm wondering if I've spotted what the problem may be.....

You've drawn the gears in a position where the centre gear is "defying gravity". Should it be allowed to fall, it would naturally move into tighter mesh with both axles pinions...at the same time. And depending on the direction of rotation, this would naturally force the gears into tighter mesh...resulting in friction and/or jamming.

You do need to lift the lower half of the centre shaft journal up...sufficient to prevent tighter meshing. And probably lift the worm up as well to allow float in an upward vertical direction....rather than downward.
Doug Kightley
Webmaster here and volunteer at the National Tramway Museum http://www.tramway.co.uk

ConnorL
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Re: SD70M - Powered

Post by ConnorL »

Whoa! I forgot about that, good catch! I think that might be the problem! I'll go ahead and fix it up then order another test print (Just the bogie) with other trains.

I agree what you're saying, it is too tight when the gear falls in place. I'll post an update of the bogie here to make sure that it looks good before wasting another $15 in 3D printing.

ConnorL
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Re: SD70M - Powered

Post by ConnorL »

Here's the updated bogie, the placement of the middle gear had been moved. What do you think? Do you think this will work?

Image

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Re: SD70M - Powered

Post by Slarge »

Also the gear is mounted in the bogie and will twist (in relation to the worm) when on a corner so the width of the gear becomes an important factor.
The space between teeth will need to accommodate the diagonal measurement of the teeth width at the angle on the curve. If they can't the worm will effectively force the spur gear downward.
Hope that makes a bit of sense?! In theory the worm should be raised a fraction making for a looser tollerence.
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ConnorL
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Re: SD70M - Powered

Post by ConnorL »

Is this better? The wormgear had been moved up 0.1mm.

Is the spacing between the middle gear and the wormgear better? Remember the wormgear have 0.05mm spacing between the bogie and itself.

Image

GarrattHamster
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Re: SD70M - Powered

Post by GarrattHamster »

To me that look's a lot better.

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Re: SD70M - Powered

Post by Slarge »

Tollerence looks good, should allow for all manner of movement.
Are you using solidworks? (if so you could animate it before printing)

ConnorL
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Re: SD70M - Powered

Post by ConnorL »

I was using Solidworks till it expired about 2 weeks ago, I'm using Autodesk Inventor right now. I used the assembly to see if there's plenty of space and...I think there is. I'm going to order these tomorrow with TTX Intermodal double stack well cars.

ConnorL
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Re: SD70M - Powered

Post by ConnorL »

Sorry, no updates so far...

Currently experimenting home-made brass etching.

This is my first attempt, I did it too quickly.

Image

robertshrives
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Location: Birmingham, UK

Re: SD70M - Powered

Post by robertshrives »

Hi great progress - looking to use the chassis on British Co - Co models so hope you get it all working well- you will have then sold three to me !
Thanks
Robert

ConnorL
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Re: SD70M - Powered

Post by ConnorL »

A small update. Brass etching was successful.

I ran into a problem... The brass sheet was not 100% brass in the middle making the etching take a long time and uneven etching.

Still first brass etch attempted ever in my entire life. I will be buying thinner and 100% pure brass.
Image

robertshrives
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Re: SD70M - Powered

Post by robertshrives »

Hi , great etchings - must be very small !! How goes the chassis?
Robert

ConnorL
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Re: SD70M - Powered

Post by ConnorL »

Hello,

Sorry for late reply, it went well.

I will keep on trying again, to make the brass etching smoother and more sharp instead of wavy as seen.

It fits well on the chassis, I'm nearly done! Just few more tweaking...then I can start focusing on the electronics.

Image

I will be making more brass handrails this weekend.

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