possible chassis for U30B et al

Re: possible chassis for U30B et al

Postby Rob M » Wed Nov 07, 2012 10:45 pm

areibel wrote:I'm asking Santa for some 9" wheelbase TT trucks?


I started working on some 9' trucks for the Lionel GP-9. Still need to do some tweeking on them (the bottom is too low, will have to make it open on bottom)
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Re: possible chassis for U30B et al

Postby railtwister » Thu Nov 08, 2012 10:21 am

Rob M wrote:
areibel wrote:I'm asking Santa for some 9" wheelbase TT trucks?


I started working on some 9' trucks for the Lionel GP-9. Still need to do some tweeking on them (the bottom is too low, will have to make it open on bottom)
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Hi Rob (Santa),

The 9' power truck looks good, what material is it made of, and what are you using for the gears?

Bill in FtL
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Re: possible chassis for U30B et al

Postby Rob M » Thu Nov 08, 2012 10:36 am

The housing and lower gears are made from ABS, the same as the gondolas & railboxes. The worm is a brass one from Kato, along with their bearing blocks. I want to get one of these finished and let it run for a few days to see how the ABS gears hold up.

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Re: possible chassis for U30B et al

Postby scaro » Wed Dec 12, 2012 10:02 am

looks good, rob. let us know how it goes.
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Re: possible chassis for U30B et al

Postby scaro » Tue Jan 29, 2013 8:56 pm

areibel wrote:(snip)

The inside of the GP shell is a little less than 13 MM, so in order to make a radius of less than about 6 feet they need a lot more space to swivel. My best guess for HO was using narrowed Athearn axles and gears in an etched fold up truck/ gearbox with an N scale worm, if I could get it to all fit up together.
Remind me again why we picked this scale? :wtf:


Al, did you calculate what the hood room needed was for a GP truck to swivel to the correct amount? i'm poring over the SD24 and wondering first, if an N worm couldn't be used, but also trying to work out what the minimum gear tower width could be for a 9'4" TT truck. i think it is possible to be brutal and remove enough material from the atlas HO truck to get the gear tower to 7mm wide. this would entail removing a clip on plastic part that protects the worm, so it'd be open. would that be enough to get a loco around a sharp curve?
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Re: possible chassis for U30B et al

Postby areibel » Tue Jan 29, 2013 10:51 pm

Hi Ben,
I didn't really calculate anything, my geometry isn't that good! I did do some crude drawings based on what I knew- with a wall thickness of around .040, that would leave an interior space of just over 13mm inside a six foot hood. I drew two parallel lines 13mm apart, cut out a rectangle and tried to estimate what clearances I'd have with different set ups. Stone age technology, I really need to learn CAD! I think by best guess was around 15 or 16 inches for a minimum radius.
The best N scale candidate I found for the GP was the Atlas N scale Alco C628 truck, the wheelbase is close for a TT scale Bloomberg. But it had it's problems- you need to remove the center wheelsets but keep the axle in place, and you need a bushing about .080 by 2mm with a 1mm stub axle to mount to the Atlas centers (using NWSL wheels). Now for an SD you could use an N scale Bloomberg truck for two axles and hang a dummy axle either inboard or outboard to get the third axle. The N scale truck is only a half a scale inch off, but you'd still need an adaptor to mount the wheels. I thought about looking for 2mm brass tubing with a 1mm bore to try cobbling somethig together, but along came Bull Ants and it mostly got shoved aside. I thought it would be a cure all, but the work that Alex and Rob are doing looks much better!
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Re: possible chassis for U30B et al

Postby ConducTTor » Wed Jan 30, 2013 3:22 am

13mm inside the hood. As for the width of the gearbox/truck, it depends on where the swivel itself is on the truck (it's possible to be off center forward or backward) and the truck itself.
My website: http://www.ttnut.com
It's the website you're already on. But if you want to be even more on it, click the link.
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Re: possible chassis for U30B et al

Postby scaro » Wed Jan 30, 2013 10:29 am

Hi

I've got two C628 trucks and have ordered some bespoke wheels. From what I can see, if you can get a 8.46mm (40" TT) dia wheel milled so it has a stub axle that is 1.5mm per side longer than the existing Atlas wheel, with a 1.2mm long needlepoint, you can insert them into the gear muff and use the same pickup arrangement as on the Atlas truck, but respaced wider. I hope the guy can do them.

However if he cannot, Plan B is getting NWSL code 88 8.17mm (28"HO) wheels drilled for a 1mm axle. Is this why you are saying you need a bushing, Al ? I believe NWSL should be able to do the wheels as a special order drilled for a 1mm axle in the first place.

These NWSL wheels need N scale 1mm axles tapped through them. (These axles are used on Mehano and Rivarossi and most old N wagons, two old N boxcars will give enough for a loco.) The pointed axle end should stay 1.2mm from the wheel face, so it can engage with the brass pickups. Getting these exact may be the trick. The other end of the 1mm dia axle can form a stub axle, and as above, these stubs must be 1.5mm longer each side than the existing Atlas wheel (so you can space the new wheels 3mm wider for 12mm gauge.)

However the pickups are going to need mounting further out. Styrene glued to the gearcase sides? Maybe rash words, but I don't think this should be that hard. You are just connecting the power source in exactly the same way the Atlas does, but with the whole thing stretched wider. The pickups will I assume need brass shim soldered to them so they will connect where they are supposed to on the chassis underside.

The centre wheel. Really, why not just leave the bulk of it there ? It will help the gear stay in place and rotate properly. If you mill the flange and axle needlepoints off those centre wheels, could they not just stay where they are? ... behind an AAR-B truck or a Blomberg they may not even be visible- the leaf spring should obscure them mostly. As long as they don't interfere with the track ... and given new larger dia wheels on the other two axles, they should be lifted out of harm's way?

This is my thinking anyhow. The spacing is exactly 9'4" with a 31' wheelbase, so I'd like to use it for an RS1 which probably needs a lower chassis. I'd like to do GP7s with Lok N Roll and then look at what Alex and RobM are doing for things like GP30s /GP35s that need to be longer.

A warning too ... the similar Atlas RSD 4/5 trucks are no good in this capacity. They are only powered on the first and middle axles; if you use them you will end up with a B- truck powered on only the front axle.
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Re: possible chassis for U30B et al

Postby areibel » Wed Jan 30, 2013 10:56 am

Hi Ben,
On the bushing, that was my thought to make the axle a little stronger. The "stock" NWSL wheels I bought come with a 2mm bore, which isn't exactly a match to the Atlas axle but it's closer than the stub.. IIRC the Atlas axle snaps into the bottom of the truck, and the N scale wheels are up tight against the ends of the axle, the stub slides completely into the plastic. If you're going to push out the wheels .060 on each side to go to TT gauge you're going to be supporting the weight of the locomotive on those little 1mm stubs, I'm afraid what that would do to the plastic axle ends over time. And getting it to hold gauge might be a problem too? If you used a piece of 2mm x 1mm tubing, even make it long enough so you have the .060 plus the width of the wheel, you could press it into the wheel then use a 1mm shaft epoxied into the wheel/bushing/axle assembly to give it some strength. You'd still have an insulated axle (unless you got too crazy with the 1mm shaft), the brass tubing/bushing could even be used as an electrical pick up from the wheels, etc.. I'd have to dig it out and look again, but I think when I looked at the electrical pick up I wasn't sure how reliable it would be if you just tried to bend the Atlas pick ups out enough to touch. I hadn't thought about trying to shim the existing pick ups out, That might help with mounting the sideframes too but I had just thought of some bronze phosphor wire as a wheel wiper or as a pick up on the bushings.
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Re: possible chassis for U30B et al

Postby scaro » Wed Jan 30, 2013 11:25 am

Hi Al, you make a good point on the stubs and the potential for bowing, food for thought.

I've got some code 88 28" (HO) wheels drilled for 2mm axles on the way too, and I might give them a whirl for this ... Reason I ordered them was, I had another 'fit of regauging madness' in relation to the N scale Spectrum SD45 and the alco RSC2. ;-)
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