Soma automatica de input por classe

[laracdp@hotmail.com 0]

<script type="text/javascript">
$(document).ready(function(){
$('#form_prepare').submit(function(){
var $this = $( this );
 
function getMoney( el ){
var money = id( el ).value.replace( ',', '.' );
return parseFloat( money )*100;
}
 
var tr = '<tr>'+
'<td>'+$this.find("input[name='descricao']").val()+'</td>'+
'<td>'+$this.find("input[name='qtd']").val()+'</td>'+
'<td><input type="hidden" class="valorAmortizar" value="'+$this.find("input[name='qtd']").val()+'" />'+$this.find("input[name='qtd']").val()+'</td>'+
'<td><input type="hidden" class="valorAmortizars" value="'+$this.find("input[name='valor_unitario']").val()+'" />'+$this.find("input[name='valor_unitario']").val()+'</td>'+
 
 
'<td><input type="text" class="total_item" value="'+$this.find("input[name='qtd']").val()  *  $this.find("input[name='valor_unitario']").val()+'" /></td>'+
 
 
'<td> <button onclick="RemoveTableRow(this)" class="btn btn-danger" type="button"><span class="glyphicon glyphicon-trash" aria-hidden="true"></span> Remover</button></td>'+
'</tr>'
$('#grid').find('tbody').append( tr );
 
return false;
});
});
</script>
<h6>Detalhamento da Despesa</h6><hr>
<form action="" method="post" OnSubmit="soma()" id="form_prepare">
<div class="row">
<div class="col-md-8">
<label>Descrição</label>
<input type="text" onkeyup="maiuscula(this)" maxlength="100" class="form-control" name="descricao" id="descricao" required="">
</div>
</div>
 
<div class="row">
<div class="col-md-2">
<label>Quantidade</label>
<input type="text" maxlength="13" onkeypress="javascript: return EntradaNumerico(event);"   class="form-control" name="qtd" id="qtd" required="">
</div>
<div class="col-md-2">
<label>Valor Unitário(R$)</label>
<input type="text"  maxlength="14" onkeypress="return(MascaraMoeda(this,'.',',',event))" class="form-control" name="valor_unitario" id="valor_unitario" required="">
</div>
</div>
<div class="row" align="center"><br>
<button name="ok" type="submit" OnSubmit="soma()" class="btn btn-success">Adicionar</button>
<button class="btn btn-primary" type="reset">Novo</button>
</form>
</div>
<div class="row" ><br>
<table id="grid" class="table table-hover">
<thead>
 <tr>
<th>Descrição</th>
<th>Qtd.</th>
<th>Qtd. Disponível</th>
<th>Valor Unitário</th>
<th></th>
 </tr>
</thead>
<tbody>
 
</tbody>
</table>
<label>Total (R$)</label>
<input type="text" id="resultado" readonly="readonly" class="form-control" onblur="return(MascaraMoeda(this,'.',',',event))" />
</div>
 

 

não estou conseguindo somar os inputs pela classe, são campos dinamicos