Vendors hear from student teams at the end of every term. The messages that get a reply look like a customer question: one constraint, one part, one date. The messages that get silence are project tours with a hope that someone will design the thing for you.
You are allowed to ask. You are not owed a free design review. Write the scoped question.
Expertise, not a tour
Ask a busy expert. Show the constraint. Show the part or the class of part you already picked. Ask whether it meets the constraint, or which of two catalogue numbers does. That is answerable from a spec they already own.
"We are a senior-design team building a robot for a class, here is our story" is not a question. Respect their time. They will not watch a video to find the ask.
If a measurement is a guess, label it. A confident load your assistant estimated is how you get a yes that fails on the bench.
Do not invent a purchase order, a company name, or a budget. If the course gave you a number, use that number. If it did not, omit money.
One owner, one date
Name the person on the team who will read the reply. A generic "our team" is how the answer lands in a mailbox nobody checks.
Give the date you will freeze the design, and say you will pick the conservative option if you do not hear. That default is how you stop waiting on a stranger.
A sufficient reply is yes, no, or a catalogue pointer. Tell them a polite decline is welcome. Student teams sometimes forget that vendors may say no.
They get email; you approve the send
They are almost certainly not on RelayLink. The send is email and a link. If they happen to have an account, you need an accepted contact — the refusal will not tell you which.
You draft. You read the part numbers. You confirm the send. A vendor should not receive a fabricated spec because the model completed a sentence.
No attachments. Datasheets live on their site. The briefing is the question.
Nicknames stay private unless you share them. Write the names on the course roster.
If they block you, the block is silent. Use the public contact form they already publish.
When the question fits on a datasheet line, connect your assistant and send that line — not the tour.