I'm thinking about getting a locomotive might be an athearn genesis 4-8-8-4 or a 4-8-4 Niagara.
Which do you like better and what radius should i use?
I like the bigboy, but in trems of radius, use the largest you can use on your layout. I would use a minimum radius of at least 24" with either engine for best results, but they may just barely make 22" radius.
I would check the stated minimum radius for the Big Boy. That loco is essentially the equivalent of a 4-8-4 in terms of rigid wheelbase, but I don't know offhand what degree of flex Athearn may have built into the model. For both locos, you are going to have to be careful with large overhang on curves. If you have double track curves, you'll probably need at least 3" of track separation to avoid scraping cars on the outside track of the curves.
Please note that ABC's recommendations work well for N scale, and are rather tight for HO. 36" is a fairly good minimum radius for larger steam, but there are many models (brass) that require more.
Quote from: Nigel on January 21, 2010, 11:04:14 PM
Please note that ABC's recommendations work well for N scale, and are rather tight for HO. 36" is a fairly good minimum radius for larger steam, but there are many models (brass) that require more.
Athearn's website states that the HO BigBoy was manufactured to be able to run on 22" radius, but if I were running it I would run it on a much larger radius, but some people can't fit curves larger than 22-24 inches.
The Athearn Big Boy and Challenger will either one work on 22" although they will both look horrible. The boiler is so far out of line with the front engine that you'll probably think it's off track from time to time when it isn't. The lead truck on the Challenger is prone to coming off track easily on 22" and I would suspect the Big Boy would be the same although I only have Challengers but have run other folks Big Boys a bit. 32" to 36" is the best with the 32" being about the minimum I'd personally recommend since it's the tightest radius the engines start to look reasonable on.
As for the 4-8-4, I have BLI Niagaras and they run quite well all the way down to 22" even though they, too, look much better on 30" or larger.
Regards
On my layout, I have a minimum radius of 24", but my minimum is about 30" on all my mainlines. I never run anything that is large (i.e. passenger cars or anything else greater than 80 feet long) on anything other than my 30" radius mainline. I usually try to avoid trouble, but no matter what you do it seems you always will have some problems.
I have the Lionel HO Challenger. I have run it on as small as 20" curves. It does not have problems of derailing. (of course I am at slow speeds!!)
It is a superb engine. I bought it at a steal, and wished I had bought more.
The Lionel Challenger is manufactured a lot differently than the Athearn Big Boy and Challenger and likewise has no impact on what radius curves the Atheran locomotives are able to make, but if someone wanted to know about the Lionel model, they're in luck.