"A train is like this."
Translation:Ilyen egy vonat.
Hungarian doesn't use van or vannak in copula sentences. That are sentences of the type "[Subject] is [quality]", for example:
- Ez vonat. - This is a train.
- A házak zöldek. - The houses are green.
- János orvos. - János is a doctor.
- A barátaim nagyszerűek. - My friends are great.
However, the other conjugations of van are still used, either regarding other grammatical persons, or for sentences in the past tense:
- Ez volt vonat. - This was a train.
- A házak zöldek voltak. - The houses were green.
- Orvos vagyok. - I am a doctor.
- Nagyszerűek voltatok. - You were great.
And van and vannak are used in question of existence, location, or time, i.e. external properties:
- Ott van a vonat. - The train is there.
- Vannak zöld házak. - There are green houses.
- Az orvos az irodája van. - The doctor is in her office.
- Barátaim vannak. - I have friends. (lit. "Friends exist for me")
That doesn't mean the same because it actually doesn't include a predicate, not even implied. It's really just "a train like this".
If you want to say a whole sentence, you should say "Egy vonat olyan, mint ez." and I don't think it sounds similar to the original sentence. It sounds like you are pointing at something visually illustrating what "a train" is similar to.
The same for "Egy olyan vonat, mint ez." It can be "This is a train like this" or just "a train like this" - but it's still about stricter, demonstrated similarity.